1
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Okuzono Y, Miyakawa S, Itou T, Sagara M, Iwata M, Ishizuchi K, Sekiguchi K, Motegi H, Oyama M, Warude D, Kikukawa Y, Suzuki S. B-cell immune dysregulation with low soluble CD22 levels in refractory seronegative myasthenia gravis. Front Immunol 2024; 15:1382320. [PMID: 38711503 PMCID: PMC11071663 DOI: 10.3389/fimmu.2024.1382320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 04/01/2024] [Indexed: 05/08/2024] Open
Abstract
Myasthenia gravis (MG), primarily caused by acetylcholine receptor (AChR) autoantibodies, is a chronic autoimmune disorder causing severe muscle weakness and fatigability. In particular, seronegative MG constitutes 10%-15% of MG cases and presents diagnostic challenges especially in early-onset female patients who often show severe disease and resistance to immunosuppressive therapy. Furthermore, the immunopathology of seronegative MG remains unclear. Thus, in this study, we aimed to elucidate the pathogenic mechanism of seronegative MG using scRNA-seq analysis and plasma proteome analysis; in particular, we investigated the relationship between immune dysregulation status and disease severity in refractory seronegative MG. Employing single-cell RNA-sequencing and plasma proteome analyses, we analyzed peripheral blood samples from 30 women divided into three groups: 10 healthy controls, 10 early-onset AChR-positive MG, and 10 refractory early-onset seronegative MG patients, both before and after intravenous immunoglobulin treatment. The disease severity was evaluated using the MG-Activities of Daily Living (ADL), MG composite (MGC), and revised 15-item MG-Quality of Life (QOL) scales. We observed numerical abnormalities in multiple immune cells, particularly B cells, in patients with refractory seronegative MG, correlating with disease activity. Notably, severe MG cases had fewer regulatory T cells without functional abnormalities. Memory B cells were found to be enriched in peripheral blood cells compared with naïve B cells. Moreover, plasma proteome analysis indicated significantly lower plasma protein levels of soluble CD22, expressed in the lineage of B-cell maturation (including mature B cells and memory B cells), in refractory seronegative MG patients than in healthy donors or patients with AChR-positive MG. Soluble CD22 levels were correlated with disease severity, B-cell frequency, and RNA expression levels of CD22. In summary, this study elucidates the immunopathology of refractory seronegative MG, highlighting immune disorders centered on B cells and diminished soluble CD22 levels. These insights pave the way for novel MG treatment strategies focused on B-cell biology.
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Affiliation(s)
- Yuumi Okuzono
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Shuuichi Miyakawa
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Tatsuo Itou
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Masaki Sagara
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Masashi Iwata
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Kei Ishizuchi
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Koji Sekiguchi
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Haruhiko Motegi
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
- Department of Neurology, The Jikei University School of Medicine, Tokyo, Japan
| | - Munenori Oyama
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
| | - Dnyaneshwar Warude
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Yusuke Kikukawa
- Oncology Drug Discovery Unit Japan, Research, Takeda Pharmaceutical Company Limited, Kanagawa, Japan
| | - Shigeaki Suzuki
- Department of Neurology, Keio University School of Medicine, Tokyo, Japan
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2
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Wong KL, Li Z, Ma F, Wang D, Song N, Chong CH, Luk KK, Leung SO. SM03, an Anti-CD22 Antibody, Converts Cis-to- Trans Ligand Binding of CD22 against α2,6-Linked Sialic Acid Glycans and Immunomodulates Systemic Autoimmune Diseases. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2022; 208:2726-2737. [PMID: 35688465 DOI: 10.4049/jimmunol.2100820] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 03/08/2022] [Indexed: 06/15/2023]
Abstract
SM03, an anti-CD22 recombinant IgG1 mAb, is currently in a phase III clinical trial for the treatment of rheumatoid arthritis (NCT04312815). SM03 showed good safety and efficacy in phase I systemic lupus erythematosus and phase II moderate to severe rheumatoid arthritis clinical trials. We propose the success of SM03 as a therapeutic to systemic autoimmune diseases is through the utilization of a novel mechanism of action unique to SM03. CD22, an inhibitory coreceptor of the BCR, is a potential immunotherapeutic target against autoimmune diseases. SM03 could disturb the CD22 homomultimeric configuration through disrupting cis binding to α2,6-linked sialic acids, induce rapid internalization of CD22 from the cell surface of human B cells, and facilitate trans binding between CD22 to human autologous cells. This in turn increased the activity of the downstream immunomodulatory molecule Src homology region 2 domain-containing phosphatase 1 (SHP-1) and decreased BCR-induced NF-κB activation in human B cells and B cell proliferation. This mechanism of action gives rationale to support the significant amelioration of disease and good safety profile in clinical trials, as by enabling the "self" recognition mechanism of CD22 via trans binding to α2,6 sialic acid ligands on autologous cells, SM03 specifically restores immune tolerance of B cells to host tissues without affecting the normal B cell immune response to pathogens.
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Affiliation(s)
- Kin L Wong
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Zhengdong Li
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Felix Ma
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Dong Wang
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Nan Song
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Chi H Chong
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Ka K Luk
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
| | - Shui O Leung
- SinoMab BioScience Ltd., Hong Kong Special Administrative Region, China
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3
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Getahun A. Role of inhibitory signaling in peripheral B cell tolerance*. Immunol Rev 2022; 307:27-42. [PMID: 35128676 PMCID: PMC8986582 DOI: 10.1111/imr.13070] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 12/16/2022]
Abstract
At least 20% of B cells in the periphery expresses an antigen receptor with a degree of self-reactivity. If activated, these autoreactive B cells pose a risk as they can contribute to the development of autoimmune diseases. To prevent their activation, both B cell-intrinsic and extrinsic tolerance mechanisms are in place in healthy individuals. In this review article, I will focus on B cell-intrinsic mechanisms that prevent the activation of autoreactive B cells in the periphery. I will discuss how inhibitory signaling circuits are established in autoreactive B cells, focusing on the Lyn-SHIP-1-SHP-1 axis, how they contribute to peripheral immune tolerance, and how disruptions of these circuits can contribute to the development of autoimmunity.
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Affiliation(s)
- Andrew Getahun
- Department of Immunology and Microbiology University of Colorado SOM Aurora Colorado USA
- Department of Immunology and Genomic Medicine National Jewish Health Denver Colorado USA
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4
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Lennon CS, Cao H, Hall AM, Vickers MA, Barker RN. The red blood cell as a novel regulator of human B-cell activation. Immunology 2021; 163:436-447. [PMID: 33728669 PMCID: PMC8274151 DOI: 10.1111/imm.13327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 02/12/2021] [Accepted: 03/01/2021] [Indexed: 01/08/2023] Open
Abstract
Non‐immune cells are increasingly recognized as important in regulating immunity, but the role of red blood cells (RBC) remains relatively unexplored, despite their abundance in the circulation and a cell surface rich in potential ligands. Here, we determine whether RBC influence the activation state of human B cells. Separation of RBC from peripheral blood mononuclear cells increased B‐cell expression of HLA‐DR/DP/DQ, whilst reconstitution reduced the levels of B‐cell activation markers HLA‐DR/DP/DQ, CD86, CD69 and CD40, as well as decreasing proliferative responses and IgM secretion. Inhibition of B cells required contact with RBC and was abrogated by either removal of sialic acids from RBC or blocking the corresponding lectin receptor CD22 on B cells. Chronic lymphocytic leukaemia B cells express low levels of CD22 and were less susceptible to inhibition by RBC, which may contribute to their activated phenotype. Taken together, the results identify a novel mechanism that may suppress inappropriate responsiveness of healthy B cells whilst circulating in the bloodstream.
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Affiliation(s)
| | - Huan Cao
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Andrew M Hall
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Mark A Vickers
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Robert N Barker
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
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5
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Mathias LM, Stohl W. Systemic lupus erythematosus (SLE): emerging therapeutic targets. Expert Opin Ther Targets 2020; 24:1283-1302. [PMID: 33034541 DOI: 10.1080/14728222.2020.1832464] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a heterogeneous clinical presentation whose etiologies are multifactorial. A myriad of genetic, hormonal, immunologic, and environmental factors contribute to its pathogenesis, and its diverse biological basis and phenotypic presentations make development of therapeutics difficult. In the past decade, tens of therapeutic targets with hundreds of individual candidate therapeutics have been investigated. AREAS COVERED We used a PUBMED database search through April 2020 to review the relevant literature. This review discusses therapeutic targets in the adaptive and innate immune systems, specifically: B cell surface antigens, B cell survival factors, Bruton's tyrosine kinase, costimulators, IL-12/IL-23, the calcineurin pathway, the JAK/STAT pathway, and interferons. EXPERT OPINION Our ever-improving understanding of SLE pathophysiology in the past decade has allowed us to identify new therapeutic targets. Multiple new drugs are on the horizon that target different elements of the adaptive and innate immune systems. SLE research remains challenging due to the heterogenous clinical presentation of SLE, confounding from background immunosuppressives being taken by SLE patients, animal models that inadequately recapitulate human disease, and imperfect and complicated outcome measures. Despite these limitations, research is promising and ongoing. The search for new therapies that target specific elements of SLE pathophysiology are discussed as well as key findings, pitfalls, and questions surrounding these targets.
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Affiliation(s)
- Lauren M Mathias
- Division of Rheumatology, Department of Medicine, University of Southern California Keck School of Medicine , Los Angeles, CA, USA
| | - William Stohl
- Division of Rheumatology, Department of Medicine, University of Southern California Keck School of Medicine , Los Angeles, CA, USA
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6
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Abstract
Sialic acid-binding immunoglobulin-type lectins (Siglecs) are expressed on the majority of white blood cells of the immune system and play critical roles in immune cell signaling. Through recognition of sialic acid-containing glycans as ligands, they help the immune system distinguish between self and nonself. Because of their restricted cell type expression and roles as checkpoints in immune cell responses in human diseases such as cancer, asthma, allergy, neurodegeneration, and autoimmune diseases they have gained attention as targets for therapeutic interventions. In this review we describe the Siglec family, its roles in regulation of immune cell signaling, current efforts to define its roles in disease processes, and approaches to target Siglecs for treatment of human disease.
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Affiliation(s)
- Shiteng Duan
- Departments of Molecular Medicine, and Immunology and Microbiology, Scripps Research, La Jolla, California 92037, USA;
| | - James C Paulson
- Departments of Molecular Medicine, and Immunology and Microbiology, Scripps Research, La Jolla, California 92037, USA;
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7
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Almaani S, Rovin BH. B-cell therapy in lupus nephritis: an overview. Nephrol Dial Transplant 2019; 34:22-29. [PMID: 30165690 DOI: 10.1093/ndt/gfy267] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/13/2018] [Indexed: 12/28/2022] Open
Abstract
Systemic lupus erythematosus (SLE) is an autoimmune multisystem disease that commonly affects the kidneys. It is characterized by persistent autoantibody production that targets a multitude of self-antigens. B-cells, plasmablasts and plasma cells, as the source of these autoantibodies, play a major role in the development of lupus nephritis (LN), and are therefore promising therapeutic targets. To date, however, randomized clinical trials of B-cell therapies in LN have not lived up to expectations, whereas uncontrolled cohort and observational studies of B-cell antagonists have been more promising. In this article, we will review the current experience with B-cell therapy in LN and highlight the pitfalls that may have limited their success. We will conclude by suggesting B-cell-centric approaches to the management of LN based on what has been learned from the overall B-cell experience in SLE.
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Affiliation(s)
- Salem Almaani
- Division of Nephrology, Department of Internal Medicine and Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, USA
| | - Brad H Rovin
- Division of Nephrology, Department of Internal Medicine and Davis Heart and Lung Research Institute, The Ohio State University Medical Center, Columbus, OH, USA
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8
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Wasim L, Buhari FHM, Yoganathan M, Sicard T, Ereño-Orbea J, Julien JP, Treanor B. N-Linked Glycosylation Regulates CD22 Organization and Function. Front Immunol 2019; 10:699. [PMID: 31019513 PMCID: PMC6458307 DOI: 10.3389/fimmu.2019.00699] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Accepted: 03/14/2019] [Indexed: 11/29/2022] Open
Abstract
The organization and clustering of cell surface proteins plays a critical role in controlling receptor signaling; however, the biophysical mechanisms regulating these parameters are not well understood. Elucidating these mechanisms is highly significant to our understanding of immune function in health and disease, given the importance of B cell receptor (BCR) signaling in directing B cells to produce antibodies for the clearance of pathogens, and the potential deleterious effects of dysregulated BCR signaling, such as in B cell malignancies or autoimmune disease. One of main inhibitory co-receptors on B cells is CD22, a sialic-acid binding protein, which interacts homotypically with other sialylated CD22 molecules, as well as heterotypically with IgM and CD45. Although the importance of CD22 in attenuating BCR signaling is well established, we still do not fully understand what mediates CD22 organization and association to BCRs. CD22 is highly glycosylated, containing 12 N-linked glycosylation sites on its extracellular domain, the function of which remain to be resolved. We were interested in how these glycosylation sites mediate homotypic vs. heterotypic interactions. To this end, we mutated five out of the six N-linked glycosylation residues on CD22 localized closest to the sialic acid binding site. Glycan site N101 was not mutated as this resulted in lack of CD22 expression. We used dual-color super-resolution imaging to investigate the impact of altered glycosylation of CD22 on the nanoscale organization of CD22 and its association with BCR. We show that mutation of these five glycosylation sites increased the clustering tendency of CD22 and resulted in higher density CD22 nanoclusters. Consistent with these findings of altered CD22 organization, we found that mutation of N-glycan sites attenuated CD22 phosphorylation upon BCR stimulation, and consequently, increased BCR signaling. Importantly, we identified that these sites may be ligands for the soluble secreted lectin, galectin-9, and are necessary for galectin-9 mediated inhibition of BCR signaling. Taken together, these findings implicate N-linked glycosylation in the organization and function of CD22, likely through regulating heterotypic interactions between CD22 and its binding partners.
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Affiliation(s)
- Laabiah Wasim
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | | | - Myuran Yoganathan
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Taylor Sicard
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - June Ereño-Orbea
- The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Jean-Philippe Julien
- Department of Immunology, University of Toronto, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Bebhinn Treanor
- Department of Immunology, University of Toronto, Toronto, ON, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada.,Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
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9
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Clark EA, Giltiay NV. CD22: A Regulator of Innate and Adaptive B Cell Responses and Autoimmunity. Front Immunol 2018; 9:2235. [PMID: 30323814 PMCID: PMC6173129 DOI: 10.3389/fimmu.2018.02235] [Citation(s) in RCA: 110] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 09/07/2018] [Indexed: 12/12/2022] Open
Abstract
CD22 (Siglec 2) is a receptor predominantly restricted to B cells. It was initially characterized over 30 years ago and named “CD22” in 1984 at the 2nd International workshop in Boston (1). Several excellent reviews have detailed CD22 functions, CD22-regulated signaling pathways and B cell subsets regulated by CD22 or Siglec G (2–4). This review is an attempt to highlight recent and possibly forgotten findings. We also describe the role of CD22 in autoimmunity and the great potential for CD22-based immunotherapeutics for the treatment of autoimmune diseases such as systemic lupus erythematosus (SLE).
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Affiliation(s)
- Edward A Clark
- Department of Immunology, University of Washington, Seattle, WA, United States.,Division of Rheumatology, Department of Medicine, University of Washington, Seattle, WA, United States
| | - Natalia V Giltiay
- Division of Rheumatology, Department of Medicine, University of Washington, Seattle, WA, United States
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10
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Özgör L, Meyer SJ, Korn M, Terörde K, Nitschke L. Sialic Acid Ligand Binding of CD22 and Siglec-G Determines Distinct B Cell Functions but Is Dispensable for B Cell Tolerance Induction. THE JOURNAL OF IMMUNOLOGY 2018; 201:2107-2116. [DOI: 10.4049/jimmunol.1800296] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 07/27/2018] [Indexed: 12/20/2022]
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11
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Taher TE, Bystrom J, Ong VH, Isenberg DA, Renaudineau Y, Abraham DJ, Mageed RA. Intracellular B Lymphocyte Signalling and the Regulation of Humoral Immunity and Autoimmunity. Clin Rev Allergy Immunol 2017; 53:237-264. [PMID: 28456914 PMCID: PMC5597704 DOI: 10.1007/s12016-017-8609-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
B lymphocytes are critical for effective immunity; they produce antibodies and cytokines, present antigens to T lymphocytes and regulate immune responses. However, because of the inherent randomness in the process of generating their vast repertoire of antigen-specific receptors, B cells can also cause diseases through recognizing and reacting to self. Therefore, B lymphocyte selection and responses require tight regulation at multiple levels and at all stages of their development and activation to avoid diseases. Indeed, newly generated B lymphocytes undergo rigorous tolerance mechanisms in the bone marrow and, subsequently, in the periphery after their migration. Furthermore, activation of mature B cells is regulated through controlled expression of co-stimulatory receptors and intracellular signalling thresholds. All these regulatory events determine whether and how B lymphocytes respond to antigens, by undergoing apoptosis or proliferation. However, defects that alter regulated co-stimulatory receptor expression or intracellular signalling thresholds can lead to diseases. For example, autoimmune diseases can result from altered regulation of B cell responses leading to the emergence of high-affinity autoreactive B cells, autoantibody production and tissue damage. The exact cause(s) of defective B cell responses in autoimmune diseases remains unknown. However, there is evidence that defects or mutations in genes that encode individual intracellular signalling proteins lead to autoimmune diseases, thus confirming that defects in intracellular pathways mediate autoimmune diseases. This review provides a synopsis of current knowledge of signalling proteins and pathways that regulate B lymphocyte responses and how defects in these could promote autoimmune diseases. Most of the evidence comes from studies of mouse models of disease and from genetically engineered mice. Some, however, also come from studying B lymphocytes from patients and from genome-wide association studies. Defining proteins and signalling pathways that underpin atypical B cell response in diseases will help in understanding disease mechanisms and provide new therapeutic avenues for precision therapy.
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Affiliation(s)
- Taher E Taher
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK
| | - Jonas Bystrom
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK
| | - Voon H Ong
- Centre for Rheumatology and Connective Tissue Diseases, Royal Free Hospital, University College London, London, UK
| | | | - Yves Renaudineau
- Immunology Laboratory, University of Brest Medical School, Brest, France
| | - David J Abraham
- Centre for Rheumatology and Connective Tissue Diseases, Royal Free Hospital, University College London, London, UK
| | - Rizgar A Mageed
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK.
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12
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Abstract
An important underlying mechanism that contributes to autoimmunity is the loss of inhibitory signaling in the immune system. Sialic acid-recognizing Ig superfamily lectins or Siglecs are a family of cell surface proteins largely expressed in hematopoietic cells. The majority of Siglecs are inhibitory receptors expressed in immune cells that bind to sialic acid-containing ligands and recruit SH2-domain-containing tyrosine phosphatases to their cytoplasmic tails. They deliver inhibitory signals that can contribute to the constraining of immune cells, and thus protect the host from autoimmunity. The inhibitory functions of CD22/Siglec-2 and Siglec-G and their contributions to tolerance and autoimmunity, primarily in the B lymphocyte context, are considered in some detail in this review. The relevance to autoimmunity and unregulated inflammation of modified sialic acids, enzymes that modify sialic acid, and other sialic acid-binding proteins are also reviewed.
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Affiliation(s)
- Vinay S Mahajan
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA.,Departments of Medicine and Pathology, Harvard Medical School, Boston, MA, USA.,Deaprtment of Pathology, Brigham and Women's Hospital, Boston, MA, USA
| | - Shiv Pillai
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA.,Departments of Medicine and Pathology, Harvard Medical School, Boston, MA, USA
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13
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Müller J, Lunz B, Schwab I, Acs A, Nimmerjahn F, Daniel C, Nitschke L. Siglec-G Deficiency Leads to Autoimmunity in Aging C57BL/6 Mice. THE JOURNAL OF IMMUNOLOGY 2015; 195:51-60. [PMID: 25987743 DOI: 10.4049/jimmunol.1403139] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 04/20/2015] [Indexed: 01/06/2023]
Abstract
Siglec-G, a member of the sialic acid-binding Ig-like lectin (Siglec) family, is expressed on B cell and dendritic cell surfaces. It acts as an inhibitory coreceptor and modulates B cell activation, especially on B1 cells, as Siglec-G-deficient mice show mainly a B1 cell-restricted phenotype resulting in increased B1 cell numbers. Although higher B1 cell numbers are discussed to be associated with autoimmunity, loss of Siglec-G does not result in autoimmune disease in BALB/c mice. However, there is evidence from Siglec-G × CD22 double-deficient mice and Siglec-G(-/-) mice on an autoimmune-prone MRL/lpr background that Siglec-G is important to maintain tolerance in B cells. In this study, we analyzed the role of Siglec-G in induction and maintenance of B cell tolerance on C57BL/6 background and in the FcγRIIb-deficient background. We find that aging Siglec-G-deficient and Siglec-G × FcγRIIb double-deficient mice develop an autoimmune phenotype with elevated autoantibody levels and mild glomerulonephritis. Aging Siglec-G-deficient mice have elevated numbers of plasma cells and germinal center B cells, as well as a higher number of activated CD4 T cells, which likely all contribute to autoantibody production. Additional loss of the inhibitory receptor FcγRIIb in Siglec-G(-/-) mice does not result in exacerbation of disease. These results indicate that Siglec-G is important to maintain tolerance in B cells and prevent autoimmunity.
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Affiliation(s)
- Jennifer Müller
- Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany; and
| | - Benjamin Lunz
- Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany; and
| | - Inessa Schwab
- Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany; and
| | - Andreas Acs
- Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany; and
| | - Falk Nimmerjahn
- Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany; and
| | - Christoph Daniel
- Department of Nephropathology, University of Erlangen-Nuremberg, 91058 Erlangen, Germany
| | - Lars Nitschke
- Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany; and
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14
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Baba Y, Kurosaki T. Role of Calcium Signaling in B Cell Activation and Biology. Curr Top Microbiol Immunol 2015; 393:143-174. [PMID: 26369772 DOI: 10.1007/82_2015_477] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Increase in intracellular levels of calcium ions (Ca2+) is one of the key triggering signals for the development of B cell response to the antigen. The diverse Ca2+ signals finely controlled by multiple factors participate in the regulation of gene expression, B cell development, and effector functions. B cell receptor (BCR)-initiated Ca2+ mobilization is sourced from two pathways: one is the release of Ca2+ from the intracellular stores, endoplasmic reticulum (ER), and other is the prolonged influx of extracellular Ca2+ induced by depleting the stores via store-operated calcium entry (SOCE) and calcium release-activated calcium (CRAC) channels. The identification of stromal interaction molecule 1(STIM1), the ER Ca2+ sensor, and Orai1, a key subunit of the CRAC channel pore, has now provided the tools to understand the mode of Ca2+ influx regulation and physiological relevance. Herein, we discuss our current understanding of the molecular mechanisms underlying BCR-triggered Ca2+ signaling as well as its contribution to the B cell biological processes and diseases.
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Affiliation(s)
- Yoshihiro Baba
- Laboratory for Lymphocyte Differentiation, WPI Immunology Frontier Research Center (IFReC), Osaka University, Suita, Osaka, 565-0871, Japan. .,Laboratory for Lymphocyte Differentiation, RIKEN Center for Integrative Medical Sciences (IMS), Kanagawa, Yokohama, 230-0045, Japan.
| | - Tomohiro Kurosaki
- Laboratory for Lymphocyte Differentiation, WPI Immunology Frontier Research Center (IFReC), Osaka University, Suita, Osaka, 565-0871, Japan.,Laboratory for Lymphocyte Differentiation, RIKEN Center for Integrative Medical Sciences (IMS), Kanagawa, Yokohama, 230-0045, Japan
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15
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Nitschke L. CD22 and Siglec-G regulate inhibition of B-cell signaling by sialic acid ligand binding and control B-cell tolerance. Glycobiology 2014; 24:807-17. [PMID: 25002414 DOI: 10.1093/glycob/cwu066] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
CD22 and Siglec-G are two B-cell expressed members of the Siglec (sialic acid-binding immunoglobulin (Ig)-like lectin) family and are potent inhibitors of B-cell signaling. Genetic approaches have provided evidence that this inhibition of B-cell antigen receptor (BCR) signaling by Siglecs is dependent on ligand binding to sialic acids in specific linkages. The cis-ligand-binding activity of CD22 leads to homo-oligomer formation, which are to a large extent found in membrane domains that are distinct from those containing the BCR. In contrast, Siglec-G is recruited via sialic acid binding to the BCR. This interaction of Siglec-G with mIgM leads to an inhibitory function that seems to be specific for B-1 cells. Both CD22 and Siglec-G control B-cell tolerance and loss of these proteins, its ligands or its inhibitory pathways can increase the susceptibility for autoimmune diseases. CD22 is a target protein both in B-cell leukemias and lymphomas, as well as in B-cell mediated autoimmune diseases. Both antibodies and synthetic chemically modified sialic acids are currently tested to target Siglecs on B cells.
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Affiliation(s)
- Lars Nitschke
- Division of Genetics, Department of Biology, University of Erlangen, Erlangen, Germany
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Angata T. Associations of genetic polymorphisms of Siglecs with human diseases. Glycobiology 2014; 24:785-93. [PMID: 24841380 DOI: 10.1093/glycob/cwu043] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Genetic polymorphism studies in humans provide unique opportunities to understand human biology and the mechanisms of diseases. Correlations between polymorphisms in the genes encoding human Siglecs and various diseases have been reported. Leading examples, such as the CD33 polymorphism associated with late-onset Alzheimer's disease, are well supported by genetic replication and mechanistic studies, while some others (such as SIGLEC8 polymorphism associated with bronchial asthma and SIGLEC14 polymorphism associated with exacerbation of chronic obstructive pulmonary disease) may benefit reinforcement by independent genetic replication or mechanistic studies. In a few cases, such as MAG polymorphism associated with psychological disorder and CD22 polymorphism associated with autoimmune disease, the phenotype associated with a genetic polymorphism of a Siglec gene and that of an enzyme gene involved in the biosynthesis of Siglec ligand show some overlap, providing indirect support for the observed genotype-phenotype association. Although studies using engineered mutant mice have provided invaluable insights into the biological functions and mechanisms of diseases, it is not always possible to develop appropriate mouse model to replicate human situations because of significant species-to-species differences, which can be a major obstacle in understanding the biology of some of human CD33/Siglec-3-related Siglecs. Further studies in genetic polymorphisms of human Siglecs, combined with appropriate functional studies, may reveal unexpected biological roles of human Siglecs, and identify possible targets for prevention and/or treatment of certain diseases.
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Affiliation(s)
- Takashi Angata
- Institute of Biological Chemistry, Academia Sinica, 128 Academia Road, Section 2, Nankang District, Taipei 11529, Taiwan
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Abstract
A high proportion of peripheral human B cells produce polyreactive or autoreactive antibodies, which indicates that they have escaped the elimination of self-reactive B cells in the bone marrow. CD22 and Siglec-G are two inhibitory receptors of the sialic-acid-binding immunoglobulin-like lectin (Siglec) family that inhibit the B-cell antigen receptor (BCR) signal. The ability of these two receptors to bind sialic acids is crucial for regulating inhibition and inducing tolerance to self-antigens. Sialylated glycans are usually absent on microbes (although several pathogenic microorganisms have evolved strategies to mimic self by decorating their surfaces with sialic acids) but abundant in higher vertebrates and might, therefore, provide an important tolerogenic signal. Combined Siglec-G deficiency and CD22 deficiency leads to spontaneous autoimmunity in mice, and mutations in an enzyme that modifies Siglec ligands are directly linked to several autoimmune diseases in humans. New data show that high-affinity ligands for CD22 and Siglec-G can be used to induce antigen-specific B-cell tolerance, which might be one strategy for the treatment of autoimmune diseases in the future.
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Bökers S, Urbat A, Daniel C, Amann K, Smith KGC, Espéli M, Nitschke L. Siglec-G deficiency leads to more severe collagen-induced arthritis and earlier onset of lupus-like symptoms in MRL/lpr mice. THE JOURNAL OF IMMUNOLOGY 2014; 192:2994-3002. [PMID: 24600033 DOI: 10.4049/jimmunol.1303367] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Siglec-G is a member of the sialic acid-binding Ig-like lectin (Siglec) family expressed on all B cells. Siglec-G-deficient mice show a large expansion of the B1 cell compartment, demonstrating the crucial role of Siglec-G as an inhibitory receptor on this cellular subset. Although Siglec-G-deficient mice did not develop spontaneous autoimmunity, mice double-deficient for Siglec-G and the related Siglec protein CD22 did show autoimmunity at an older age. In this study, we addressed the question of whether loss of Siglec G on its own affects disease severity in animal models of rheumatoid arthritis and systemic lupus erythematosus. Siglec-G-deficient mice showed moderately increased clinical severity and higher inflammation of the knee joints following collagen-induced arthritis, when compared with control mice. The Siglec-G-deficient mouse was also backcrossed to the autoimmune prone MLR/lpr background. Although both Siglec-G-deficient and control MRL/lpr mice developed a lupus-like disease, Siglec-G-deficient MRL/lpr mice showed an earlier occurrence of autoantibodies; a higher lymphoproliferation of B and T cells; and an earlier onset of disease, as shown by proteinuria and glomerular damage in the kidney. Moreover, Siglec-G-deficient female mice showed a significantly reduced survival compared with female control MRL/lpr mice. Thus, the loss of the inhibitory receptor Siglec-G led to a moderate exacerbation of disease severity and early onset in both collagen-induced arthritis and spontaneous lupus nephritis in MRL/lpr mice.
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Affiliation(s)
- Susanne Bökers
- Division of Genetics, Department of Biology, University of Erlangen-Nürnberg, 91058 Erlangen, Germany
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Taher TE, Muhammad HA, Rahim A, Flores-Borja F, Renaudineau Y, Isenberg DA, Mageed RA. Aberrant B-lymphocyte responses in lupus: inherent or induced and potential therapeutic targets. Eur J Clin Invest 2013; 43:866-80. [PMID: 23701475 DOI: 10.1111/eci.12111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 04/29/2013] [Indexed: 12/11/2022]
Abstract
BACKGROUND Lupus is a prototype autoimmune disease of unknown aetiology. The disease is complex; manifest diverse clinical symptoms and disease mechanisms. This complexity has provided many leads to explore: from disease mechanisms to approaches for therapy. B-lymphocytes play a central role in the pathogenesis of the disease. However, the cause of aberrant B-lymphocyte responses in patients and, indeed, its causal relationship with the disease remain unclear. DESIGN This article provides a synopsis of current knowledge of immunological abnormalities in lupus with an emphasis on abnormalities in the B-lymphocyte compartment. RESULTS There is evidence for abnormalities in most compartments of the immune system in animal models and patients with lupus including an ever expanding list of abnormalities within the B-lymphocyte compartment. In addition, recent genome-wide linkage analyses in large cohorts of patients have identified new sets of genetic association factors some with potential links with defective B-lymphocyte responses although their full pathophysiological effects remain to be determined. The accumulating knowledge may help in the identification and application of new targeted therapies for treating lupus disease. CONCLUSIONS Cellular, molecular and genetic studies have provided significant insights into potential causes of immunological defects associated with lupus. Most of this insight relate to defects in B- and T-lymphocyte tolerance, signalling and responses. For B-lymphocytes, there is evidence for altered regulation of inter and intracellular signalling pathways at multiple levels. Some of these abnormalities will be discussed within the context of potential implications for disease pathogenesis and targeted therapies.
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Affiliation(s)
- Taher E Taher
- Bone & Joint Research Unit, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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Taher TE, Muhammad HA, Bariller E, Flores-Borja F, Renaudineau Y, Isenberg DA, Mageed RA. B-lymphocyte signalling abnormalities and lupus immunopathology. Int Rev Immunol 2013; 32:428-44. [PMID: 23768155 DOI: 10.3109/08830185.2013.788648] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lupus is a complex autoimmune rheumatic disease of unknown aetiology. The disease is associated with diverse features of immunological abnormality in which B-lymphocytes play a central role. However, the cause of atypical B-lymphocyte responses remains unclear. In this article, we provide a synopsis of current knowledge on intracellular signalling abnormalities in B-lymphocytes in lupus and their potential effects on the response of these cells in mouse models and in patients. There are numerous reported defects in the regulation of intracellular signalling proteins and pathways in B-lymphocytes in lupus that, potentially, affect critical biological responses. Most of the evidence for these defects comes from studies of disease models and genetically engineered mice. However, there is also increasing evidence from studying B-lymphocytes from patients and from genome-wide linkage analyses for parallel defects to those observed in mice. These studies provide molecular and genetic explanations for the key immunological abnormalities associated with lupus. Most of the new information appears to relate to defects in intracellular signalling that impact B-lymphocyte tolerance, cytokine production and responses to infections. Some of these abnormalities will be discussed within the context of disease pathogenesis.
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Affiliation(s)
- Taher E Taher
- Bone & Joint Research Unit, William Harvey Research Institute, Barts
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21
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Walker JA, Hall AM, Kotsopoulou E, Espeli M, Nitschke L, Barker RN, Lyons PA, Smith KGC. Increased red cell turnover in a line of CD22-deficient mice is caused by Gpi1c: a model for hereditary haemolytic anaemia. Eur J Immunol 2012; 42:3212-22. [PMID: 22930244 DOI: 10.1002/eji.201242633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Revised: 08/02/2012] [Accepted: 08/24/2012] [Indexed: 11/06/2022]
Abstract
CD22, an inhibitory co-receptor of the BCR, has been identified as a potential candidate gene for the development of autoimmune haemolytic anaemia in mice. In this study, we have examined Cd22(tm1Msn) CD22-deficient mice and identified an increase in RBC turnover and stress erythropoiesis, which might be consistent with haemolysis. We then, however, eliminated CD22 deficiency as the cause of accelerated RBC turnover and established that enhanced RBC turnover occurs independently of B cells and anti-RBC autoanti-bodies. Accelerated RBC turnover in this particular strain of CD22-deficient mice is red cell intrinsic and appears to be the consequence of a defective allele of glucose phosphate isomerase, Gpi1(c). This form of Gpi1 was originally derived from wild mice and results in a substantial reduction in enzyme activity. We have identified the polymorphism that causes impaired catalytic activity in the Gpi1(c) allele, and biochemically confirmed an approximate 75% reduction of GPI1 activity in Cd22(-/-) RBCs. The Cd22(-/-).Gpi1(c) congenic mouse provides a novel animal model of GPI1-deficiency, which is one of the most common causes of chronic non-spherocytic haemolytic anaemia in humans.
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Affiliation(s)
- Jennifer A Walker
- Cambridge Institute for Medical Research and Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK
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22
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CD22 and Siglec-G in B cell function and tolerance. Trends Immunol 2012; 33:413-20. [PMID: 22677186 DOI: 10.1016/j.it.2012.04.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 03/31/2012] [Accepted: 04/27/2012] [Indexed: 12/15/2022]
Abstract
The immune system has evolved into two main arms: the primitive innate arm that is the first line of defense but relatively short-lived and broad acting; and the advanced adaptive arm that generates immunological memory, allowing rapid, specific recall responses. T cell-independent type-2 (TI-2) antigens (Ags) invoke innate immune responses. However, due to its 'at the ready' nature, how the innate arm of the immune system maintains tolerance to potentially abundant host TI-2 Ags remains elusive. Therefore, it is important to define the mechanisms that establish innate immune tolerance. This review highlights recent insights into B cell tolerance to theoretical self TI-2 Ags, and examines how the B cell-restricted sialic acid binding Ig-like lectins (Siglecs), CD22 and Siglec-G, might contribute to this process.
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Paulson JC, Macauley MS, Kawasaki N. Siglecs as sensors of self in innate and adaptive immune responses. Ann N Y Acad Sci 2012; 1253:37-48. [PMID: 22288608 DOI: 10.1111/j.1749-6632.2011.06362.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Siglecs are expressed on most white blood cells of the immune system and are known to modulate the activity of cell signaling receptors via regulatory motifs in their cytoplasmic domains. This immunoglobulin subfamily of coreceptors recognize sialic acid containing glycans as ligands, which are found on glycoproteins and glycolipids of all mammalian cells. By virtue of their ability to recognize this common structural element, siglecs are increasingly recognized for their ability to help immune cells distinguish between self and nonself, and dampen autoimmune responses.
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Affiliation(s)
- James C Paulson
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA.
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24
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Jellusova J, Nitschke L. Regulation of B cell functions by the sialic acid-binding receptors siglec-G and CD22. Front Immunol 2012; 2:96. [PMID: 22566885 PMCID: PMC3342095 DOI: 10.3389/fimmu.2011.00096] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 12/28/2011] [Indexed: 01/08/2023] Open
Abstract
B cell antigen receptor (BCR) engagement can lead to many different physiologic outcomes. To achieve an appropriate response, the BCR signal is interpreted in the context of other stimuli and several additional receptors on the B cell surface participate in the modulation of the signal. Two members of the Siglec (sialic acid-binding immunoglobulin-like lectin) family, CD22 and Siglec-G have been shown to inhibit the BCR signal. Recent findings indicate that the ability of these two receptors to bind sialic acids might be important to induce tolerance to self-antigens. Sialylated glycans are usually absent on microbes but abundant in higher vertebrates and might therefore provide an important tolerogenic signal. Since the expression of the specific ligands for Siglec-G and CD22 is tightly regulated and since Siglecs are not only able to bind their ligands in trans but also on the same cell surface this might provide additional mechanisms to control the BCR signal. Although both Siglec-G and CD22 are expressed on B cells and are able to inhibit BCR mediated signaling, they also show unique biological functions. While CD22 is the dominant regulator of calcium signaling on conventional B2 cells and also seems to play a role on marginal zone B cells, Siglec-G exerts its function mainly on B1 cells and influences their lifespan and antibody production. Both Siglec-G and CD22 have also recently been linked to toll-like receptor signaling and may provide a link in the regulation of the adaptive and innate immune response of B cells.
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BAFF and innate immunity: new therapeutic targets for systemic lupus erythematosus. Immunol Cell Biol 2012; 90:293-303. [PMID: 22231653 DOI: 10.1038/icb.2011.111] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Recently, the B cell has emerged as a cornerstone of systemic lupus erythematosus (SLE) pathogenesis. This has been highlighted by studies of the cytokine B-cell-activating factor of the tumour necrosis factor (TNF) family (BAFF), a crucial factor regulating B-cell maturation, survival and function. Overexpression of BAFF in mice leads to the development of an SLE-like disease, independent of T cells but instead relying on innate immunity mechanisms. Moreover, BAFF has been shown to be elevated in the serum of patients suffering from autoimmune conditions, especially SLE, and may correlate with disease activity. These findings challenge the previous notion that T:B-cell collaboration is the sole driver of SLE. In recent years, controlled trials have for the first time tested targeted therapeutics for SLE. However, agents designed to target B cells failed to meet primary endpoints in clinical trials in SLE, suggesting that a more complex role for B cells in SLE awaited elucidation. By contrast, on 9 March 2011, the US Food and Drug Administration approved belimumab, a fully human anti-BAFF monoclonal antibody, as a new B-cell-specific treatment for SLE. This article will review over 10 years of research on the BAFF system, key findings that led to this recent positive clinical outcome and propose a model potentially explaining why this B-cell-specific therapy has yielded positive results in clinical trials. We will also review promising therapies presently in clinical trials targeting innate immunity, which are likely to revolutionize SLE management towards a personalized and targeted therapy approach.
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Sang A, Yin Y, Zheng YY, Morel L. Animal Models of Molecular Pathology. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 105:321-70. [DOI: 10.1016/b978-0-12-394596-9.00010-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Traczewski P, Rudnicka L. Treatment of systemic lupus erythematosus with epratuzumab. Br J Clin Pharmacol 2011; 71:175-82. [PMID: 21219397 DOI: 10.1111/j.1365-2125.2010.03767.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Systemic lupus erythematosus is a prototypic autoimmune disease characterized by abnormalities in the activity of B-cells and T-cells. A novel specific treatment for autoimmune diseases is B-cell depletion with monoclonal antibodies. Epratuzumab is a monoclonal antibody that targets CD22 antigen on B-cells. Initial phase II and two terminated early phase III studies suggest that treatment of systemic lupus erythematosus with this immunomodulatory agent is effective, well tolerated and significantly improves the patient's quality of life. In vitro studies and clinical trials with non-Hodgkin lymphoma patients indicate epratuzumab can potentially serve as a complementary drug in combination therapy with another inhibitor of B-cell activity, rituximab, which is a monoclonal anti-CD20 antibody.
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Kawasaki N, Rademacher C, Paulson JC. CD22 regulates adaptive and innate immune responses of B cells. J Innate Immun 2010; 3:411-9. [PMID: 21178327 DOI: 10.1159/000322375] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 10/29/2010] [Indexed: 01/01/2023] Open
Abstract
B cells sense microenvironments through the B cell receptor (BCR) and Toll-like receptors (TLRs). While signals from BCR and TLRs synergize to distinguish self from nonself, inappropriate regulation can result in development of autoimmune disease. Here we show that CD22, an inhibitory co-receptor of BCR, also negatively regulates TLR signaling in B cells. CD22-deficient (Cd22(-/-)) B cells exhibit hyperactivation in response to ligands of TLRs 3, 4 and 9. Evidence suggests that this results from impaired induction of suppressors of cytokine signaling 1 and 3, well-known suppressors of TLR signaling. Antibody-mediated sequestration of CD22 on wild-type (WT) B cells augments proliferation by TLR ligands. Conversely, expression of CD22 in a Cd22(-/-) B cell line blunts responses to TLR ligands. We also show that lipopolysaccharide-induced transcription by nuclear factor-κB is inhibited by ectopic expression of CD22 in a TLR4 reporter cell line. Taken together, these results suggest that negative regulation of TLR signaling is an intrinsic property of CD22. Since TLRs and BCR activate B cells through different signaling pathways, and are differentially localized in B cells, CD22 exhibits a broader regulation of receptors that mediate adaptive and innate immune responses of B cells than previously recognized.
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Affiliation(s)
- Norihito Kawasaki
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA 92037, USA
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29
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Duong BH, Tian H, Ota T, Completo G, Han S, Vela JL, Ota M, Kubitz M, Bovin N, Paulson JC, Paulson J, Nemazee D. Decoration of T-independent antigen with ligands for CD22 and Siglec-G can suppress immunity and induce B cell tolerance in vivo. ACTA ACUST UNITED AC 2009; 207:173-87. [PMID: 20038598 PMCID: PMC2812539 DOI: 10.1084/jem.20091873] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Autoreactive B lymphocytes first encountering self-antigens in peripheral tissues are normally regulated by induction of anergy or apoptosis. According to the “two-signal” model, antigen recognition alone should render B cells tolerant unless T cell help or inflammatory signals such as lipopolysaccharide are provided. However, no such signals seem necessary for responses to T-independent type 2 (TI-2) antigens, which are multimeric antigens lacking T cell epitopes and Toll-like receptor ligands. How then do mature B cells avoid making a TI-2–like response to multimeric self-antigens? We present evidence that TI-2 antigens decorated with ligands of inhibitory sialic acid–binding Ig-like lectins (siglecs) are poorly immunogenic and can induce tolerance to subsequent challenge with immunogenic antigen. Two siglecs, CD22 and Siglec-G, contributed to tolerance induction, preventing plasma cell differentiation or survival. Although mutations in CD22 and its signaling machinery have been associated with dysregulated B cell development and autoantibody production, previous analyses failed to identify a tolerance defect in antigen-specific mutant B cells. Our results support a role for siglecs in B cell self-/nonself-discrimination, namely suppressing responses to self-associated antigens while permitting rapid “missing self”–responses to unsialylated multimeric antigens. The results suggest use of siglec ligand antigen constructs as an approach for inducing tolerance.
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Affiliation(s)
- Bao Hoa Duong
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA
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Santiago-Raber ML, Baudino L, Izui S. Emerging roles of TLR7 and TLR9 in murine SLE. J Autoimmun 2009; 33:231-8. [PMID: 19846276 DOI: 10.1016/j.jaut.2009.10.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by B cell hyperactivity leading to the production of various autoantibodies and subsequent development of glomerulonephritis, i.e. lupus nephritis. Among the principal targets of autoantibodies produced in murine SLE are nucleic acid-protein complexes, such as chromatin and ribonucleoproteins, and the envelope glycoprotein gp70 of endogenous retroviruses. The preferential production of these autoantibodies is apparently promoted by the presence of genetic abnormalities leading to defects in the elimination of apoptotic cells and to an enhanced expression of endogenous retroviruses. Moreover, recent studies revealed that the innate receptors TLR7 and TLR9 are critically involved in the activation of dendritic cells and autoreactive B cells through the recognition of endogenous DNA- or RNA-containing antigens and subsequent development of autoimmune responses against nuclear autoantigens. Furthermore, the regulation of autoimmune responses against endogenous retroviral gp70 by TLR7 suggested the implication of endogenous retroviruses in this autoimmune response. Clearly, further elucidation of the precise molecular role of TLR7 and TLR9 in the development of autoimmune responses will help to develop novel therapeutic strategies and targets for SLE.
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Affiliation(s)
- Marie-Laure Santiago-Raber
- Department of Pathology and Immunology, Centre Medical Universitaire, University of Geneva, 1211 Geneva 4, Switzerland
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Haraldsson MK, Louis-Dit-Sully CA, Lawson BR, Sternik G, Santiago-Raber ML, Gascoigne NRJ, Theofilopoulos AN, Kono DH. The lupus-related Lmb3 locus contains a disease-suppressing Coronin-1A gene mutation. Immunity 2008; 28:40-51. [PMID: 18199416 PMCID: PMC2274909 DOI: 10.1016/j.immuni.2007.11.023] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 11/12/2007] [Accepted: 11/28/2007] [Indexed: 10/22/2022]
Abstract
Here, we show that a lupus-suppressing locus is caused by a nonsense mutation of the filamentous actin-inhibiting Coronin-1A gene. This mutation was associated with developmental and functional alterations in T cells including reduced migration, survival, activation, and Ca2+ flux. T-dependent humoral responses were impaired, but no intrinsic B cell defects were detected. By transfer of T cells, it was shown that suppression of autoimmunity could be accounted for by the presence of the Coro1a(Lmb3) mutation in T cells. Our results demonstrate that Coronin-1A is required for the development of systemic lupus and identify actin-cytoskeleton regulatory proteins as potential targets for modulating autoimmune diseases.
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Affiliation(s)
| | | | - Brian R. Lawson
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
| | - Gabriel Sternik
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
| | | | | | | | - Dwight H. Kono
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
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Abstract
CD22 is an inhibitory coreceptor of the B-cell receptor (BCR), and plays a critical role in establishing signalling thresholds for B-cell activation. Like other coreceptors, the ability of CD22 to modulate B-cell signalling is critically dependent upon its proximity to the BCR, and this in turn is governed by the binding of its extracellular domain to alpha2,6-linked sialic acid ligands. Manipulation of CD22 ligand binding in various experimental settings has profound effects on B-cell signalling, but as yet there is no complete model for how ligand binding in vivo controls normal CD22 function. Several elegant studies have recently shed light on this issue, although the results appear to suggest two mutually exclusive models for the role of ligand binding; in either promoting or inhibiting, CD22 function. We shall therefore discuss these results in detail, and suggest possible approaches by which these conflicting experimental findings might be reconciled. We shall also consider a second important issue in CD22 biology, which relates to the role that defects in this receptor might play in mediating autoimmune disease. We review the current evidence for this, and discuss the importance of genetic background in modifying CD22 function and predisposition to autoimmunity.
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Affiliation(s)
- Jennifer A Walker
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Cambridge CB2 0XY, United Kingdom.
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Misu N, Zhang M, Mori S, Miyazaki T, Furukawa H, Sasaki T, Nose M, Ono M. Autosomal loci associated with a sex-related difference in the development of autoimmune phenotypes in a lupus model. Eur J Immunol 2007; 37:2787-96. [PMID: 17823981 DOI: 10.1002/eji.200637016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Sex-related differences (SrD) are a general characteristic of human autoimmune diseases. There is an increasing body of evidence that suggests a link between sex-related hormones and autoimmune onsets. Here, through a genetic approach using a lupus mouse model, we attempted to show the involvement of genetic factors in the development of SrD in autoimmune diseases. Using MRL/lpr x (MRL/lpr x C57BL/6.Fas(lpr))F1 (MBN2) mice, the whole genome was searched to identify linkage loci to autoimmune phenotypes inherited from a lupus MRL/Mp.Fas(lpr) (MRL/lpr) strain of mice, which exhibits glomerulonephritis, splenomegaly and antinuclear autoantibody. The genome-wide association study confirmed four linkage loci on chromosomes 4, 7, 13, and 17. Furthermore, differential analyses performed using male and female groups of MBN2 mice revealed that two loci located on chromosomes 4 (41-72 cM, MRL/lpr allele) and 7 (4-21 cM, B6/lpr allele) were male specific and suppressed autoimmune phenotypes. Notably, the sum effect of the two loci adequately explained a range of SrD developed in the MBN2 mice. Our present findings suggest the presence of a male-predominant mechanism underlying the development of SrD in autoimmunity, depending on the effects of autosomal loci under an undefined male-specific condition.
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Affiliation(s)
- Naoko Misu
- Department of Pathology, Tohoku University Graduate School of Medicine, Sendai, Japan
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35
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Nakatani K, Qu WM, Zhang MC, Fujii H, Furukawa H, Miyazaki T, Iwano M, Saito Y, Nose M, Ono M. A genetic locus controlling aging-sensitive regression of B lymphopoiesis in an autoimmune-prone MRL/lpr strain of mice. Scand J Immunol 2007; 66:654-61. [PMID: 17983422 DOI: 10.1111/j.1365-3083.2007.02020.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aging readily affects immune system under the influence of environmental and/or intrinsic factors while accelerating the development of various immune disorders including autoimmune diseases. Little is known about molecular and cellular mechanisms connecting between immune senescence and development of autoimmune diseases. Here, we first show strain-specific and aging-sensitive onset of B-cell abnormality in a lupus-prone MRL/Mp.Fas(lpr) (MRL/lpr) strain of mice. This abnormality was characterized by the regression of B lymphopoiesis in the bone marrow of this strain. We next examined the association between the B-cell regression and onset of autoimmune diseases in aged (MRL/lpr x C3H/He.Fas(lpr)) F2 mice, in which pathologic phenotypes, such as glomerulonephritis, vasculitis, sialoadenitis and arthritis, variously developed. We also searched whole genome to identify genetic loci linked to the B-cell regression by using the same F2 mice. The B-cell regression manifested in the spleen of F2 mice was retrospectively evaluated by reverse transcriptase-based PCR quantification. The results demonstrated that the onset of autoimmune diseases in the F2 mice was not associated with the aging-sensitive B-cell regression. The genetic study identified a significant locus responsible for the B-cell regression in the vicinity of D5Mit233 (29 cM). This is first evidence for the presence of a genetic locus that affects B lymphopoiesis in an aging-sensitive manner.
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Affiliation(s)
- K Nakatani
- First Department of Internal Medicine, Nara Medical University, Kashihara, Japan
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36
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Liu K, Li QZ, Yu Y, Liang C, Subramanian S, Zeng Z, Wang HW, Xie C, Zhou XJ, Mohan C, Wakeland EK. Sle3 and Sle5 can independently couple with Sle1 to mediate severe lupus nephritis. Genes Immun 2007; 8:634-45. [PMID: 17728789 DOI: 10.1038/sj.gene.6364426] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Genetic analyses of the lupus-prone NZM2410 mouse have identified multiple susceptibility loci on chromosome 7, termed Sle3 and Sle5. Both of these loci were contained within a large congenic interval, originally termed as Sle3 that strongly impacts a variety of myeloid and T-cell phenotypes and mediates fatal lupus nephritis when combined with Sle1. We have now produced two subcongenic strains, B6.Sle3 and B6.Sle5, carrying the Sle3 and Sle5 intervals separately and characterized their phenotypes as monocongenic strains and individually in combination with Sle1. Neither B6.Sle3 nor B6.Sle5 monocongenic strain develop severe autoimmunity; however, both of these intervals cause the development of severe glomerulonephritis when combined with Sle1. Thus, B6.Sle1Sle3 and B6.Sle1Sle5 exhibit splenomegaly, expansion of activated B and CD4+ T-cell populations and high levels of IgG and IgM autoantibodies targeting multiple nuclear antigens, intact glomeruli and various other autoantigens. In addition, B6.Sle1Sle3 mice also produced higher levels of IgA antinuclear autoantibodies, which were implicated in the development of IgA nephropathy. Our results indicate that Sle3 and Sle5 can independently complement with Sle1, through shared and unique mechanisms, to mediate the development of severe autoimmunity.
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Affiliation(s)
- K Liu
- Department of Immunology, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9093, USA.
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37
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Yarkoni Y, Fischel R, Kat I, Yachimovich-Cohen N, Eilat D. Peripheral B cell receptor editing may promote the production of high-affinity autoantibodies in CD22-deficient mice. Eur J Immunol 2006; 36:2755-67. [PMID: 16983722 DOI: 10.1002/eji.200636190] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
CD22-deficient mice are characterized by B cell hyperactivity and autoimmunity. We have constructed knock-in CD22-/- mice, expressing an anti-DNA heavy (H) chain (D42), alone or combined with Vkappa1-Jkappa1 or Vkappa8-Jkappa5 light (L) chains. The Ig-targeted mice produced a lupus-like serology that was age- and sex-dependent. High-affinity IgG autoantibodies were largely dependent on the selection of B cells with a particular H/L combination, in which a non-transgenic, endogenous L chain was assembled by secondary rearrangements through the mechanism of receptor editing. Moreover, we present evidence that these secondary rearrangements are very prominent in splenic peripheral B cells. Since CD22 is primarily expressed on the surface of peripheral B cells, we propose a model for the development of a lupus-like autoimmune disease by a combination of peripheral receptor editing and abnormal B cell activation.
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Affiliation(s)
- Yuval Yarkoni
- Department of Medicine, Hadassah University Hospital, Faculty of Medicine, Hebrew University, Jerusalem, Israel
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38
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Inaoki M, Echigo T, Hayashi H, Nagaoka T, Hasegawa M, Takehara K, Fujimoto W, Tedder TF, Sato S. Decreased expression levels of CD22 and L-selectin on peripheral blood B lymphocytes from patients with bullous pemphigoid. J Autoimmun 2006; 27:196-202. [PMID: 17055225 DOI: 10.1016/j.jaut.2006.09.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 09/08/2006] [Accepted: 09/12/2006] [Indexed: 12/01/2022]
Abstract
Bullous pemphigoid (BP), an autoimmune subepidermal-blistering disease of the elderly, is caused by antibodies against BP antigens at the epidermal basement membrane zone (BMZ). CD22 is a B lymphocyte specific response regulator, which is down-regulated after B-cell activation. Old CD22-deficient mice produce class-switched autoantibodies. To assess the role of CD22 in the pathogenesis of BP, we examined CD22 expression on B cells from BP patients and correlated its expression with clinical parameters. B cell expression of CD22 was 20% lower in BP patients when compared to healthy control subjects. In addition, B cells from BP patients showed decreased expression of L-selectin, which is an indicator of leukocyte activation, and CD22 expression levels were correlated with L-selectin expression. These results suggest that the decreased CD22 expression may be associated with the activation of B cells in BP. CD22 expression levels in BP patients did not correlate with the levels of anti-epidermal BMZ antibodies, and old CD22-deficient mice did not develop the anti-epidermal BMZ antibody. These results suggest that a decrease in CD22 expression may not be associated with BP-specific antibody production.
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Affiliation(s)
- Makoto Inaoki
- Department of Dermatology, Kanazawa University Graduate School of Medical Science, Kanazawa, Ishikawa, Japan.
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39
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Kono DH, Theofilopoulos AN. Genetics of SLE in mice. ACTA ACUST UNITED AC 2006; 28:83-96. [PMID: 16972052 DOI: 10.1007/s00281-006-0030-7] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Accepted: 07/04/2006] [Indexed: 01/12/2023]
Abstract
Genetic studies in spontaneous, induced, and gene-manipulated mouse models of SLE have provided significant insights into the potential number and diversity of genes that can promote, resist, and modify lupus susceptibility. Novel genes and mechanisms of disease pathogenesis have also been identified. Importantly, mouse models have provided an initial view of the genomic landscape of lupus-affecting genes, and have documented the complexities of verifying and determining the role of specific candidate loci and genes. Mouse models of lupus should continue to serve as a vital approach to defining the genetics of SLE.
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Affiliation(s)
- Dwight H Kono
- Department of Immunology/IMM3, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, 92037, USA.
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40
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Steinfeld SD, Youinou P. Epratuzumab (humanised anti-CD22 antibody) in autoimmune diseases. Expert Opin Biol Ther 2006; 6:943-9. [PMID: 16918261 DOI: 10.1517/14712598.6.9.943] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
B cells play an important role in the pathogenesis of many autoimmune diseases. Different approaches targeting the B cell compartment are under investigation. Selective modulation of B cells has been recently achieved using a humanised monoclonal antibody against the B cell surface marker CD22. This antibody (epratuzumab) was originally developed for the treatment of non-Hodgkin's lymphoma and was found to be effective, with a very good safety profile. Recent studies have demonstrated the efficacy and safety of epratuzumab in several autoimmune diseases, including systemic lupus erythematosus and primary Sjögren's syndrome.
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Affiliation(s)
- Serge D Steinfeld
- Erasme University Hospital, Department of Rheumatology, Route de Lennik 808, Brussels 1070, Belgium.
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41
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Watson LC, Moffatt-Blue CS, McDonald RZ, Kompfner E, Ait-Azzouzene D, Nemazee D, Theofilopoulos AN, Kono DH, Feeney AJ. Paucity of V-D-D-J rearrangements and VH replacement events in lupus prone and nonautoimmune TdT-/- and TdT+/+ mice. THE JOURNAL OF IMMUNOLOGY 2006; 177:1120-8. [PMID: 16818769 DOI: 10.4049/jimmunol.177.2.1120] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CDR3 regions containing two D segments, or containing the footprints of V(H) replacement events, have been reported in both mice and humans. However, the 12-23 bp rule for V(D)J recombination predicts that D-D rearrangements, which would occur between 2 recombination signal sequences (RSSs) with 12-bp spacers, should be extremely disfavored, and the cryptic RSS used for V(H) replacement is very inefficient. We have previously shown that newborn mice, which lack TdT due to the late onset of its expression, do not contain any CDR3 with D-D rearrangements. In the present study, we test our hypothesis that most D-D rearrangements are due to fortuitous matching of the second apparent D segment by TdT-introduced N nucleotides. We analyzed 518 sequences from adult MRL/lpr- and C57BL/6 TdT-deficient B cell precursors and found only two examples of CDR3 with D-D rearrangements and one example of a potential V(H) replacement event. We examined rearrangements from pre-B cells, marginal zone B cells, and follicular B cells from mice congenic for the Lbw5 (Sle3/5) lupus susceptibility loci and from other strains of mice and found very few examples of CDR3 with D-D rearrangements. We assayed B progenitor cells, and cells enriched for receptor editing, for DNA breaks at the "cryptic heptamer" but such breaks were rare. We conclude that many examples of apparent D-D rearrangements in the mouse are likely due to N additions that fortuitously match short stretches of D genes and that D-D rearrangements and V(H) replacement are rare occurrences in the mouse.
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Affiliation(s)
- Lisa C Watson
- The Scripps Research Institute, Department of Immunology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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42
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Pisitkun P, Deane JA, Difilippantonio MJ, Tarasenko T, Satterthwaite AB, Bolland S. Autoreactive B cell responses to RNA-related antigens due to TLR7 gene duplication. Science 2006; 312:1669-72. [PMID: 16709748 DOI: 10.1126/science.1124978] [Citation(s) in RCA: 674] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Antibodies against nuclear self-antigens are characteristic of systemic autoimmunity, although mechanisms promoting their generation and selection are unclear. Here, we report that B cells containing the Y-linked autoimmune accelerator (Yaa) locus are intrinsically biased toward nucleolar antigens because of increased expression of TLR7, a single-stranded RNA-binding innate immune receptor. The TLR7 gene is duplicated in Yaa mice because of a 4-Megabase expansion of the pseudoautosomal region. These results reveal high divergence in mouse Y chromosomes and represent a good example of gene copy number qualitatively altering a polygenic disease manifestation.
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Affiliation(s)
- Prapaporn Pisitkun
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases (NIAID), NIH, Rockville, MD 20852, USA
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43
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Eisenberg R. Targeting B cells in systemic lupus erythematosus: not just déjà vu all over again. Arthritis Res Ther 2006; 8:108. [PMID: 16732895 PMCID: PMC1526641 DOI: 10.1186/ar1967] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Epratuzumab (anti-CD22) is a humanized monoclonal antibody that recognizes a pan-B-cell marker. It potentially downregulates B cell activity through negative signaling, as well as depleting B cells moderately. The uncontrolled series discussed by Dörner and colleagues in this issue of Arthritis Research & Therapy suggests that epratuzumab may be safe and efficacious for systemic lupus erythematosus. A randomized controlled trial is currently active to test this possibility.
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Affiliation(s)
- Robert Eisenberg
- Division of Rheumatology, Department of Medicine, University of Pennsylvania, School of Medicine, 756 BRBII/III, 421 Curie Boulevard, Philadelphia, PA 19104-6160, USA.
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44
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Nitschke L, Lajaunias F, Moll T, Ho L, Martinez-Soria E, Kikuchi S, Santiago-Raber ML, Dix C, Parkhouse RME, Izui S. Expression of aberrant forms of CD22 on B lymphocytes in Cd22a lupus-prone mice affects ligand binding. Int Immunol 2005; 18:59-68. [PMID: 16291654 DOI: 10.1093/intimm/dxh349] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CD22 functions primarily as a negative regulator of B-cell receptor signaling. The Cd22a allele has been proposed as a candidate allele for murine systemic lupus erythematosus. In this study, we explored the possible expression of aberrant forms of CD22, which differ in the N-terminal sequences constituting the ligand-binding site due to synthesis of abnormally processed Cd22 mRNA, in several Cd22a mouse strains, including C57BL/6 Cd22 congenic mice. The staining pattern of splenic B cells obtained with CY34 anti-CD22 mAb, which was expected to bind poorly to the aberrant CD22, was more heterogeneous in Cd22(a) mice than in Cd22b mice. Moreover, CD22 detected on B cells of Cd22a mice was expressed more weakly and as a smaller-sized protein, compared with Cd22b mice. Significantly, analysis with a synthetic CD22 ligand demonstrated that Cd22a mice carried a larger proportion of CD22 that was not bound by cis ligands on the B-cell surface than Cd22b mice. Finally, the study of C57BL/6 Cd22 congenic mice revealed that Cd22a B cells displayed a phenotype reminiscent of constitutively activated B cells (reduced surface IgM expression and augmented MHC class II expression), as reported for B cells expressing a mutant CD22 lacking the ligand-binding domain. Our demonstration that Cd22a B cells express aberrant forms of CD22, which can potentially deregulate B-cell signaling because of their decreased ligand-binding capacity, provides further support for Cd22a as a potential candidate allele for murine systemic lupus erythematosus.
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MESH Headings
- Alleles
- Animals
- B-Lymphocytes/immunology
- Gene Expression Regulation/genetics
- Gene Expression Regulation/immunology
- Genes, MHC Class II/genetics
- Genes, MHC Class II/immunology
- Immunoglobulin M/genetics
- Immunoglobulin M/immunology
- Ligands
- Lupus Erythematosus, Systemic/genetics
- Lupus Erythematosus, Systemic/immunology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C3H
- Mice, Inbred NZB
- Mice, Knockout
- RNA Processing, Post-Transcriptional/genetics
- RNA Processing, Post-Transcriptional/immunology
- Sialic Acid Binding Ig-like Lectin 2/genetics
- Sialic Acid Binding Ig-like Lectin 2/immunology
- Signal Transduction/genetics
- Signal Transduction/immunology
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Affiliation(s)
- Lars Nitschke
- Department of Genetics, University of Erlangen, 91058 Erlangen, Germany
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45
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Kumar KR, Zhu J, Bhaskarabhatla M, Yan M, Mohan C. Enhanced expression of stem cell antigen-1 (Ly-6A/E) in lymphocytes from lupus prone mice correlates with disease severity. J Autoimmun 2005; 25:215-22. [PMID: 16246522 DOI: 10.1016/j.jaut.2005.09.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Revised: 06/22/2005] [Accepted: 09/07/2005] [Indexed: 12/18/2022]
Abstract
B6.Sle1 mice, congenic for the NZM2410-derived lupus susceptibility locus, Sle1 on chromosome 1 exhibit many of the features seen in human lupus including activated lymphocytes and high titers of antinuclear autoantibodies. Among the different surface molecules that were aberrantly expressed on the B6.Sle1 lymphocytes was Ly-6A/E. Splenic B- and T-lymphocytes but not myeloid cells from B6.Sle1 mice exhibited enhanced levels of Ly-6A/E compared to B6 controls. In particular, MZ B cells, GC B cells and B-cell blasts expressed the highest levels of Ly-6A/E in both strains, with the levels being even higher on B6.Sle1 derived cells. Following stimulation with LPS or anti-IgM, there was a profound up-regulation in Ly-6A/E, particularly on MZ B cells and B-cell blasts. CD4 and CD8 T cells also up-regulated Ly-6A/E after stimulation with anti-CD3 and anti-CD28. These studies were extended to additional autoimmune strains including B6.Sle3, B6.Sle1.lpr and BXSB. Importantly, Ly-6A/E levels on lymphocytes were commensurate with the degree of disease exhibited by these lupus strains. Finally, it appears that increased interferon levels, in addition to antigen receptor stimulation, may also be a factor accounting for elevated Ly-6A/E in lupus. Given these observations it is important to elucidate the functional role of Ly-6A/E in lupus in future studies.
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Affiliation(s)
- Kirthi Raman Kumar
- Department of Internal Medicine, Rheumatology, and the Center for Immunology, University of Texas Southwestern Medical School, Dallas, 75235, USA
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46
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Mattsson N, Duzevik EG, Pelsue SC. Expansion of CD22lo B cells in the spleen of autoimmune-prone flaky skin mice. Cell Immunol 2005; 234:124-32. [PMID: 16054613 DOI: 10.1016/j.cellimm.2005.06.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2005] [Revised: 06/02/2005] [Accepted: 06/11/2005] [Indexed: 11/18/2022]
Abstract
Similar to murine models with compromised CD22/SHP-1 function, flaky skin (fsn) mutant mice exhibit lymphocyte hyperactivation and an autoimmune phenotype characterized by circulating autoantibodies to dsDNA and glomerulonephritis. Immunophenotyping of fsn/fsn splenic B cells was performed to determine if abnormalities in CD22 expression contributed to the phenotype. We identified an expansion of an IgM(bright) CD22lo population consistent with immature B-lymphocytes. While normal B-lymphocytes require IL-4 to achieve down-modulation of CD22 expression in response to BCR cross-linking, culture with anti-IgM alone led to reduced CD22 expression in fsn/fsn mice. Furthermore, when IL-4 was added to fsn/fsn cultures, no further reduction in CD22 expression was observed. This suggested that fsn/fsn B cells were pre-activated in vivo by chronic IL-4 exposure. A portion of these CD22lo cells expressed the B-1 surface marker CD11b. We contend that decreased activation thresholds among CD22lo B-lymphocytes contributes to the expansion of immature and B-1 B cell populations and to the development of autoimmune pathology in fsn/fsn mice.
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Affiliation(s)
- Nancy Mattsson
- Department of Applied Medical Sciences and Bioscience Research Institute of Southern Maine, University of Southern Maine, Portland, ME 04103, USA
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47
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Abstract
Animal glycan-recognizing proteins can be broadly classified into two groups-lectins (which typically contain an evolutionarily conserved carbohydrate-recognition domain [CRD]) and sulfated glycosaminoglycan (SGAG)-binding proteins (which appear to have evolved by convergent evolution). Proteins other than antibodies and T-cell receptors that mediate glycan recognition via immunoglobulin (Ig)-like domains are called "I-type lectins." The major homologous subfamily of I-type lectins with sialic acid (Sia)-binding properties and characteristic amino-terminal structural features are called the "Siglecs" (Sia-recognizing Ig-superfamily lectins). The Siglecs can be divided into two groups: an evolutionarily conserved subgroup (Siglecs-1, -2, and -4) and a CD33/Siglec-3-related subgroup (Siglecs-3 and -5-13 in primates), which appear to be rapidly evolving. This article provides an overview of historical and current information about the Siglecs.
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Affiliation(s)
- Ajit Varki
- Research Center for Glycoscience, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan.
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48
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Kikuchi S, Amano H, Amano E, Fossati-Jimack L, Santiago-Raber ML, Moll T, Ida A, Kotzin BL, Izui S. Identification of 2 major loci linked to autoimmune hemolytic anemia in NZB mice. Blood 2005; 106:1323-9. [PMID: 15860660 PMCID: PMC1895197 DOI: 10.1182/blood-2005-02-0558] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Using a cohort of C57BL/6 (B6) x (NZB x B6)F1 backcross male mice bearing the Yaa (Y-linked autoimmune acceleration) mutation, we mapped and characterized the NZB-derived susceptibility loci predisposing to the development of autoimmune hemolytic anemia (AHA). Our analysis identified 2 major loci on NZB chromosome 7 and chromosome 1 linked with Coombs antierythrocyte autoantibody production, and their contributions were confirmed by the analysis of B6.Yaa mice (B6 mice bearing the Yaa mutation) congenic for each NZB-derived susceptibility interval. A newly identified Aia3 (autoimmune anemia 3) locus present on NZB chromosome 7 selectively regulated Coombs antibody responses, while the second locus, directly overlapping with Nba2 (NZB autoimmunity 2) on chromosome 1, promoted the development of AHA, likely as part of its effect on overall production of lupus autoantibodies. A higher incidence of Coombs antibody production in B6.Aia3 congenic mice (B6 mice bearing the NZB-Aia3 locus) than B6.Nba2 mice (B6 mice bearing the NZB-Nba2 locus) indicated a major role for Aia3 in AHA. Notably, lack of expansion of B1 cells in B6.Aia3 congenic mice argued against the involvement of this subset in AHA. Finally, our analysis of BC mice also demonstrated the presence of a B6-derived H2-linked locus on chromosome 17 that apparently regulated the production of Coombs antibodies as a result of its overall autoimmune promoting effect.
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Affiliation(s)
- Shuichi Kikuchi
- Department of Pathology and Immunology, C. M. U., 1211 Geneva 4, Switzerland
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49
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Tedder TF, Poe JC, Haas KM. CD22: A Multifunctional Receptor That Regulates B Lymphocyte Survival and Signal Transduction. Adv Immunol 2005; 88:1-50. [PMID: 16227086 DOI: 10.1016/s0065-2776(05)88001-0] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recent advances in the study of CD22 indicate a complex role for this transmembrane glycoprotein member of the immunoglobulin superfamily in the regulation of B lymphocyte survival and proliferation. CD22 has been previously recognized as a potential lectin-like adhesion molecule that binds alpha2,6-linked sialic acid-bearing ligands and as an important regulator of B-cell antigen receptor (BCR) signaling. However, genetic studies in mice reveal that some CD22 functions are regulated by ligand binding, whereas other functions are ligand-independent and may only require expression of an intact CD22 cytoplasmic domain at the B-cell surface. Until recently, most of the functional activity of CD22 has been widely attributed to CD22's ability to recruit potent intracellular phosphatases and limit the intensity of BCR-generated signals. However, a more complex role for CD22 has recently emerged, including a central role in a novel regulatory loop controlling the CD19/CD21-Src-family protein tyrosine kinase (PTK) amplification pathway that regulates basal signaling thresholds and intensifies Src-family kinase activation after BCR ligation. CD22 is also central to the regulation of peripheral B-cell homeostasis and survival, the promotion of BCR-induced cell cycle progression, and is a potent regulator of CD40 signaling. Herein we discuss our current understanding of how CD22 governs these complex and overlapping processes, how alterations in these tightly controlled regulatory activities may influence autoimmune disease, and the current and future applications of CD22-directed therapies in oncology and autoimmunity.
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Affiliation(s)
- Thomas F Tedder
- Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710, USA
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50
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Santiago-Raber ML, Laporte C, Reininger L, Izui S. Genetic basis of murine lupus. Autoimmun Rev 2004; 3:33-9. [PMID: 14871647 DOI: 10.1016/s1568-9972(03)00062-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/06/2003] [Indexed: 01/12/2023]
Abstract
Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the formation of a variety of autoantibodies and subsequent development of severe glomerulonephritis. Etiology of SLE remains unknown even if it is now well established that SLE is under polygenic control as well as the contribution of hormonal and environmental factors. The availability of several murine strains that spontaneously develop an autoimmune syndrome resembling human SLE, such as New Zealand, MRL and BXSB mice has provided useful tools for the genetic dissection of susceptibility to SLE. Moreover, development of various transgenic and mutant mice has made it possible to identify a number of susceptibility genes such as those involved in the regulation of apoptosis or B cell receptor signaling that can trigger lupus-like phenotypes. Obviously, further identification of the genetic defects present in lupus-prone mice is of paramount importance for understanding the immunopathogenesis of SLE.
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