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Ben-Ali M, Kechout N, Mekki N, Yang J, Chan KW, Barakat A, Aadam Z, Gamara J, Gargouri L, Largueche B, BelHadj-Hmida N, Nedri A, Ameur HB, Mellouli F, Boukari R, Bejaoui M, Bousfiha A, Ben-Mustapha I, Lau YL, Barbouche MR. Genetic Approaches for Definitive Diagnosis of Agammaglobulinemia in Consanguineous Families. J Clin Immunol 2019; 40:96-104. [PMID: 31696364 DOI: 10.1007/s10875-019-00706-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/09/2019] [Indexed: 11/30/2022]
Abstract
Autosomal recessive agammaglobulinemia (ARA) is a primary immunodeficiency characterized by absent peripheral B cells, severe hypogammaglobulinemia, and absent BTK gene mutations. In ARA, mutations occur in genes encoding the pre-B cell receptor (pre-BCR) or downstream signaling proteins. In this work, we used candidate gene and whole-exome sequencing to investigate the molecular basis of ARA in 6 patients from 4 consanguineous North-African families. Sanger sequencing of candidate genes encoding the pre-BCR components (ΙGΗΜ, CD79A, CD79B, IGLL1, and VPREB1) was initially performed and determined the genetic defect in five patients. Two novel mutations in IGHM (p.Val378Alafs*1 and p.Ile184Serfs*21) were identified in three patients from two unrelated kindred and a novel nonsense mutation was identified in CD79A (p.Trp66*) in two siblings from a third kindred. Whole-exome sequencing (WES) was performed on the sixth patient who harbored a homozygous stop mutation at position 407 in the RAG2 gene (p.Glu407*). We concluded that conventional gene sequencing, especially when multiple genes are involved in the defect as is the case in ARA, is costly and time-consuming, resulting in delayed diagnosis that contributes to increased morbidity and mortality. In addition, it fails to identify the involvement of novel and unsuspected gene defects when the phenotype of the patients is atypical. WES has the potential to provide a rapid and more accurate genetic diagnosis in ARA, which is crucial for the treatment of the patients.
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Affiliation(s)
- Meriem Ben-Ali
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia.,Université Tunis El Manar, 1068, Tunis, Tunisia
| | - Nadia Kechout
- Department of Immunology, Institut Pasteur d'Algérie, Algiers, Algeria.,Faculty of Medicine of Algiers, Algiers, Algeria
| | - Najla Mekki
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia.,Université Tunis El Manar, 1068, Tunis, Tunisia
| | - Jing Yang
- Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Hong Kong, China
| | - Koon Wing Chan
- Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Hong Kong, China
| | - Abdelhamid Barakat
- Laboratory of Molecular and Human Genetics, Department of Scientific Research, Institut Pasteur du Maroc, Casablanca, Morocco
| | - Zahra Aadam
- Laboratory of Molecular and Human Genetics, Department of Scientific Research, Institut Pasteur du Maroc, Casablanca, Morocco
| | - Jouda Gamara
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia.,Université Tunis El Manar, 1068, Tunis, Tunisia
| | - Lamia Gargouri
- Department of Paediatrics, Habib Bourguiba Hospital, Sfax, Tunisia
| | - Beya Largueche
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia.,Université Tunis El Manar, 1068, Tunis, Tunisia
| | - Nabil BelHadj-Hmida
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia.,Université Tunis El Manar, 1068, Tunis, Tunisia
| | - Amel Nedri
- Department of Paediatrics, Medenine Hospital, Medenine, Tunisia
| | | | - Fethi Mellouli
- National Bone Marrow Transplantation Center, Jebel Lakhdar, Tunis, Tunisia
| | - Rachida Boukari
- Department of Pediatrics, CHU Mustapha-Bacha, Faculty of Medicine of Algiers, Algiers, Algeria
| | - Mohamed Bejaoui
- National Bone Marrow Transplantation Center, Jebel Lakhdar, Tunis, Tunisia
| | - Aziz Bousfiha
- Clinical Immunology Unit, Department of Pediatrics, Centre Hospitalier Universitaire Ibn Rochd, King Hassan II University, Casablanca, Morocco
| | - Imen Ben-Mustapha
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia.,Université Tunis El Manar, 1068, Tunis, Tunisia
| | - Yu-Lung Lau
- Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Hong Kong, China
| | - Mohamed-Ridha Barbouche
- Laboratory of Transmission, Control and Immunobiology of Infections, LR11IPT02 (LTCII), Institut Pasteur de Tunis, 13, place Pasteur, BP74, 1002, Tunis-Belvédère, Tunisia. .,Université Tunis El Manar, 1068, Tunis, Tunisia.
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2
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Benhamou D, Labi V, Getahun A, Benchetrit E, Dowery R, Rajewsky K, Cambier JC, Melamed D. The c-Myc/miR17-92/PTEN Axis Tunes PI3K Activity to Control Expression of Recombination Activating Genes in Early B Cell Development. Front Immunol 2018; 9:2715. [PMID: 30524445 PMCID: PMC6262168 DOI: 10.3389/fimmu.2018.02715] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 11/05/2018] [Indexed: 11/13/2022] Open
Abstract
Appropriate PI3K signals generated by the antigen receptor are essential to promote B cell development. Regulation of recombination activating gene (RAG)-1 and RAG-2 expression is one key process that is mediated by PI3K to ensure developmental progression and selection. When PI3K signals are too high or too low, expression of RAGs does not turn off and B cell development is impaired or blocked. Yet, the mechanism which tunes PI3K activity to control RAG expression during B cell development in the bone marrow is unknown. Recently we showed that a c-Myc/miR17-92/PTEN axis regulates PI3K activity for positive and negative selection of immature B cells. Here, we show that the c-Myc/miR17-92/PTEN axis tunes PI3K activity to control the expression of RAGs in proB cells. Using different genetically engineered mouse models we show that impaired function of the c-Myc/miR17-92/PTEN axis alters the PI3K/Akt/Foxo1 pathway to result in dis-regulated expression of RAG and a block in B cell development. Studies using 38c-13 B lymphoma cells, where RAGs are constitutively expressed, suggest that this regulatory effect is mediated post-translationally through Foxo1.
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Affiliation(s)
- David Benhamou
- Department of Immunology, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Verena Labi
- Max Delbrück Center for Molecular Medicine, Berlin, Germany.,Division of Developmental Immunology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Andrew Getahun
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, United States
| | - Eli Benchetrit
- Department of Immunology, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Reem Dowery
- Department of Immunology, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Klaus Rajewsky
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - John C Cambier
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO, United States
| | - Doron Melamed
- Department of Immunology, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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3
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Lougaris V, Vitali M, Baronio M, Moratto D, Tampella G, Biasini A, Badolato R, Plebani A. Autosomal Recessive Agammaglobulinemia: The Third Case of Igβ Deficiency Due to a Novel Non-sense Mutation. J Clin Immunol 2014; 34:425-7. [DOI: 10.1007/s10875-014-0033-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 03/27/2014] [Indexed: 01/09/2023]
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4
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Huang L, Lange MD, Yu Y, Li S, Su K, Zhang Z. Contribution of V(H) replacement products in mouse antibody repertoire. PLoS One 2013; 8:e57877. [PMID: 23469094 PMCID: PMC3585286 DOI: 10.1371/journal.pone.0057877] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 01/30/2013] [Indexed: 11/19/2022] Open
Abstract
VH replacement occurs through RAG-mediated recombination between the cryptic recombination signal sequence (cRSS) near the 3′ end of a rearranged VH gene and the 23-bp RSS from an upstream unrearranged VH gene. Due to the location of the cRSS, VH replacement leaves a short stretch of nucleotides from the previously rearranged VH gene at the newly formed V-D junction, which can be used as a marker to identify VH replacement products. To determine the contribution of VH replacement products to mouse antibody repertoire, we developed a Java-based VH Replacement Footprint Analyzer (VHRFA) program and analyzed 17,179 mouse IgH gene sequences from the NCBI database to identify VH replacement products. The overall frequency of VH replacement products in these IgH genes is 5.29% based on the identification of pentameric VH replacement footprints at their V-D junctions. The identified VH replacement products are distributed similarly in IgH genes using most families of VH genes, although different families of VH genes are used differentially. The frequencies of VH replacement products are significantly elevated in IgH genes derived from several strains of autoimmune prone mice and in IgH genes encoding autoantibodies. Moreover, the identified VH replacement footprints in IgH genes from autoimmune prone mice or IgH genes encoding autoantibodies preferentially encode positively charged amino acids. These results revealed a significant contribution of VH replacement products to the diversification of antibody repertoire and potentially, to the generation of autoantibodies in mice.
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Affiliation(s)
- Lin Huang
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Miles D. Lange
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Yangsheng Yu
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Song Li
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Kaihong Su
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- The Eppley Cancer Institute, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Zhixin Zhang
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- The Eppley Cancer Institute, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- * E-mail:
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5
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Autosomal recessive agammaglobulinemia: novel insights from mutations in Ig-beta. Curr Allergy Asthma Rep 2008; 8:404-8. [PMID: 18682105 DOI: 10.1007/s11882-008-0078-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Agammaglobulinemia is a rare primary immuno-deficiency characterized by an early block of B-cell development in the bone marrow resulting in the absence of peripheral B cells and low/absent immunoglobulin serum levels. Mutations in the Bruton tyrosine kinase and in components of the pre-B-cell receptor (pre-BCR), such as mu heavy chain, surrogate light chain, and Igalpha have been found in 85% to 90% of patients affected by this disease. Here we review the recent advances in the characterization of molecular defects underlying an early block in B-cell development, focusing on the novel finding of the first two patients with agammaglobulinemia caused by mutations in Igbeta, the transmembrane protein that associates with Igalpha as part of the pre-BCR complex. Characterization of novel genetic defects involving components of the pre-BCR is crucial for a better understanding of the biology of early B-cell development and may have therapeutic and prognostic implications.
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6
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Ferrari S, Zuntini R, Lougaris V, Soresina A, Sourková V, Fiorini M, Martino S, Rossi P, Pietrogrande MC, Martire B, Spadaro G, Cardinale F, Cossu F, Pierani P, Quinti I, Rossi C, Plebani A. Molecular analysis of the pre-BCR complex in a large cohort of patients affected by autosomal-recessive agammaglobulinemia. Genes Immun 2007; 8:325-33. [PMID: 17410177 DOI: 10.1038/sj.gene.6364391] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Autosomal-recessive agammaglobulinemia is a rare and heterogeneous disorder, characterized by early-onset infections, profound hypogammaglobulinemia of all immunoglobulin isotypes and absence of circulating B lymphocytes. To investigate the molecular basis of the disease, 23 patients with early-onset disease and no mutations in Bruton tyrosine kinase, the gene responsible for X-linked agammaglobulinemia, were selected and analyzed by direct sequencing of candidate genes. Two novel mutations in the mu heavy chain (muHC) gene (IGHM) were identified in three patients belonging to two unrelated families. A fourth patient carries a previously described G>A nucleotide substitution at the -1 position of an alternative splice site in IGHM; here, we demonstrate that this mutation is indeed responsible for aberrant splicing. Comparison of bone marrow cytofluorimetric profiles in two patients carrying different mutations in the IGHM gene suggests a genotype-phenotype correlation with the stage at which B-cell development is blocked. Several new single nucleotide polymorphisms (SNPs) both in the muHC and in the lambda5-like/VpreB-coding genes were identified. Two unrelated patients carry compound heterozygous variations in the VpreB1 gene that may be involved in disease ethiology.
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Affiliation(s)
- S Ferrari
- Medical Genetics Unit and CRBa, S. Orsola-Malpighi University Hospital, via Massarenti 9, 40138 Bologna, Italy.
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7
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Herzog S, Jumaa H. The N terminus of the non-T cell activation linker (NTAL) confers inhibitory effects on pre-B cell differentiation. THE JOURNAL OF IMMUNOLOGY 2007; 178:2336-43. [PMID: 17277139 DOI: 10.4049/jimmunol.178.4.2336] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
SLP-65 and the linker for activation of T cells (LAT) are central adaptor proteins that link the activated pre-BCR to downstream events in pre-B cells. Recently, a new transmembrane adaptor called NTAL/LAB/LAT2 (hereafter called NTAL for non-T cell activation linker) with striking functional and structural similarity to LAT has been identified in B cells. In this study, we compare the function of NTAL and LAT in pre-BCR signaling and show that, in contrast to LAT, NTAL does not induce pre-BCR down-regulation, calcium flux, or pre-B cell differentiation. To test whether differences between NTAL-mediated and LAT-mediated signaling are caused by the missing phospholipase C (PLC)-gamma binding motif in NTAL, we inserted the PLC-gamma1/2 binding motif of LAT into NTAL. This insertion rendered NTAL capable of activating pre-BCR down-regulation and calcium flux. Unexpectedly however, the ability of NTAL to induce calcium flux was not sufficient to promote pre-B cell differentiation, suggesting that the PLC-gamma binding motif has only partial effects on NTAL-mediated pre-BCR signaling. By generating chimeric swap mutants, we identified the N terminus of NTAL as an inhibitory domain that prevents pre-B cell differentiation while allowing pre-BCR down-regulation and receptor-mediated calcium flux. Our data suggest that, in addition to the missing PLC-gamma1/2 binding motif, the N terminus is responsible for the functional differences between NTAL and LAT in pre-B cells.
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Affiliation(s)
- Sebastian Herzog
- Institute for Biology III, Albert-Ludwigs University of Freiburg and Max Planck Institute for Immunobiology, Freiburg, Germany
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8
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Meixlsperger S, Köhler F, Wossning T, Reppel M, Müschen M, Jumaa H. Conventional Light Chains Inhibit the Autonomous Signaling Capacity of the B Cell Receptor. Immunity 2007; 26:323-33. [PMID: 17331747 DOI: 10.1016/j.immuni.2007.01.012] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 12/14/2006] [Accepted: 01/26/2007] [Indexed: 02/06/2023]
Abstract
Signals from the B cell antigen receptor (BCR), consisting of mu heavy chain (muHC) and conventional light chain (LC), and its precursor the pre-BCR, consisting of muHC and surrogate light chain (SLC), via the adaptor protein SLP-65 regulate the development and function of B cells. Here, we compare the effect of SLC and conventional LC expression on receptor-induced Ca(2+) flux in B cells expressing an inducible form of SLP-65. We found that SLC expression strongly enhanced an autonomous ability of muHC to induce Ca(2+) flux irrespective of additional receptor crosslinking. In contrast, LC expression reduced this autonomous muHC ability and resulted in antigen-dependent Ca(2+) flux. These data indicate that autonomous ligand-independent signaling can be induced by receptor forms other than the pre-BCR. In addition, our data suggest that conventional LCs play an important role in the inhibition of autonomous receptor signaling, thereby allowing further B cell differentiation.
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Affiliation(s)
- Sonja Meixlsperger
- Institute for Biology III, Albert-Ludwigs University of Freiburg and Max Planck Institute for Immunobiology, Stuebeweg 51, 79108 Freiburg, Germany
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9
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Flemming A, Brummer T, Reth M, Jumaa H. The adaptor protein SLP-65 acts as a tumor suppressor that limits pre-B cell expansion. Nat Immunol 2003; 4:38-43. [PMID: 12436112 DOI: 10.1038/ni862] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2002] [Accepted: 10/16/2002] [Indexed: 11/08/2022]
Abstract
Mice deficient in the adaptor protein SLP-65 (also known as BLNK) have reduced numbers of mature B cells, but an increased pre-B cell compartment. We show here that compared to wild-type cells, SLP-65(-/-) pre-B cells show an enhanced ex vivo proliferative capacity. This proliferation requires interleukin 7 and expression of the pre-B cell receptor (pre-BCR). In addition, SLP-65(-/-) mice have a high incidence of pre-B cell lymphoma. Reintroduction of SLP-65 into SLP-65(-/-) pre-B cells led to pre-BCR down-regulation and enhanced differentiation. Our results indicate that SLP-65 regulates a developmental program that promotes differentiation and limits pre-B cell expansion, thereby acting as a tumor suppressor.
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Affiliation(s)
- Alexandra Flemming
- Institute for Biology III, Albert-Ludwigs University of Freiburg and Max Planck Institute for Immunobiology, Stuebeweg 51, 79108 Freiburg, Germany
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10
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Wang Y, Kanegane H, Sanal O, Tezcan I, Ersoy F, Futatani T, Miyawaki T. Novel Igalpha (CD79a) gene mutation in a Turkish patient with B cell-deficient agammaglobulinemia. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 108:333-6. [PMID: 11920841 DOI: 10.1002/ajmg.10296] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mutations that impair early B cell development result in profound antibody deficiency, which is characterized by a paucity of mature B cells and the early onset of recurrent pyogenic infections. Among these inherited early B cell defects, X-linked agammaglobulinemia (XLA) with mutations in Bruton's tyrosine kinase (BTK) gene is mostly identified. Recent studies have shown that mutations in the gene for mu heavy chain (IGHM) and for other components of the pre-B cell receptor complex, including lambda5/14.1 (IGLL1) or Igalpha (CD79a), can cause a disorder that is clinically similar to XLA. In a genetic survey of XLA in Turkey, we examined possible mutations in the IGHM, IGLL1, and Igalpha genes in some male patients with presumed XLA who did not have identifiable BTK mutations. We found an eight-year-old boy with a novel homozygous mutation in the Igalpha gene (IVS2+1G>A) causing B cell defect. This is the second case of agammaglobulinemia due to an Igalpha (CD79a) deficiency in the world.
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Affiliation(s)
- Yue Wang
- Department of Pediatrics, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan
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11
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Cancro MP, Sah AP, Levy SL, Allman DM, Schmidt MR, Woodland RT. xid mice reveal the interplay of homeostasis and Bruton's tyrosine kinase-mediated selection at multiple stages of B cell development. Int Immunol 2001; 13:1501-14. [PMID: 11717191 DOI: 10.1093/intimm/13.12.1501] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Human X-linked agammaglobulinemia (XLA) and murine X-linked immune defect (XID) are both immunodeficiencies mediated by mutations in Bruton's tyrosine kinase (Btk), yet the developmental stage(s) affected remain controversial. To further refine the placement of the XID defect(s), we used bromodeoxyuridine labeling to determine turnover, production and transition rates of developing B cell subsets in normal, xid and xid mice expressing a human Bcl-2 transgene (xid/bcl-2). We find the xid mutation manifest at two stages of B cell development. The first is early, reducing pre-B cell production by restricting pro-B to pre-B cell transit. Surprisingly, this impairment is offset by increased survival of cells progressing from the pre- to immature B cell pool, suggesting that Btk-independent homeostatic mechanisms act to maintain this compartment. The second point of action is late, substantially reducing mature B cell production. Together, these findings reconcile apparent discrepancies in the developmental stage affected by the murine versus human lesions and suggest previously unappreciated homeostatic processes that act at the pre-B to immature B cell transition. Finally, Btk likely functions differently at these two checkpoints, since ectopic Bcl-2 expression fails to directly complement the early xid lesion, yet reverses the defect impeding final B cell maturation.
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Affiliation(s)
- M P Cancro
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, 36th and Hamilton Walk, Philadelphia, PA 19104-6082, USA
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12
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Abstract
B cell development is a highly regulated process whereby functional peripheral subsets are produced from hematopoietic stem cells, in the fetal liver before birth and in the bone marrow afterward. Here we review progress in understanding some aspects of this process in the mouse bone marrow, focusing on delineation of the earliest stages of commitment, on pre-B cell receptor selection, and B cell tolerance during the immature-to-mature B cell transition. Then we note some of the distinctions in hematopoiesis and pre-B selection between fetal liver and adult bone marrow, drawing a connection from fetal development to B-1/CD5(+) B cells. Finally, focusing on CD5(+) cells, we consider the forces that influence the generation and maintenance of this distinctive peripheral B cell population, enriched for natural autoreactive specificities that are encoded by particular germline V(H)-V(L) combinations.
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Affiliation(s)
- R R Hardy
- Institute for Cancer Research, Fox Chase Cancer Center, 7701 Burholme Ave., Philadelphia, Pennsylvania 19111, USA.
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13
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The Human (ΨL+μ−) proB Complex: Cell Surface Expression and Biochemical Structure of a Putative Transducing Receptor. Blood 1999. [DOI: 10.1182/blood.v93.12.4336.412k28_4336_4346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The surrogate light chain (ΨL) associates with μ and Ig-Igβ chains to form the preB-cell receptor that plays a critical role in early B-cell differentiation. Discrepancies exist in human concerning the existence of ΨL+μ− proB cells and the biochemical structure of such a proB-cell complex remains elusive. Among new antihuman VpreB monoclonal antibodies (MoAbs), 5 of the γκ isotype bound to recombinant and native VpreB protein with high affinity. They recognized 4 discrete epitopes, upon which 2 were in the extra-loop fragment. Such MoAbs detected the ΨL at the cell surface of either preB or on both proB and preB cells. The previously reported SLC1/SLC2 MoAbs recognize a conformational epitope specific for the μ/ΨL association in accordance with their preB-cell reactivity. Using the proB/preB 4G7 MoAb, ΨL cell surface expression was detected on normal bone marrow, not only on CD34−CD19+ preB but also on CD34+CD19+ proB cells. Futhermore, this MoAb identified ΨL+μ− fresh proB leukemic cells of the TEL/AML1 type. Biochemical studies showed that, at the proB stage, the ΨL is associated noncovalently with two proteins of 105 and 130 kD. Triggering of this complex induces intracellular Ca2+ flux, suggesting that the ΨL may be involved in a new receptor at this early step of the B-cell differentiation.
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14
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The Human (ΨL+μ−) proB Complex: Cell Surface Expression and Biochemical Structure of a Putative Transducing Receptor. Blood 1999. [DOI: 10.1182/blood.v93.12.4336] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
The surrogate light chain (ΨL) associates with μ and Ig-Igβ chains to form the preB-cell receptor that plays a critical role in early B-cell differentiation. Discrepancies exist in human concerning the existence of ΨL+μ− proB cells and the biochemical structure of such a proB-cell complex remains elusive. Among new antihuman VpreB monoclonal antibodies (MoAbs), 5 of the γκ isotype bound to recombinant and native VpreB protein with high affinity. They recognized 4 discrete epitopes, upon which 2 were in the extra-loop fragment. Such MoAbs detected the ΨL at the cell surface of either preB or on both proB and preB cells. The previously reported SLC1/SLC2 MoAbs recognize a conformational epitope specific for the μ/ΨL association in accordance with their preB-cell reactivity. Using the proB/preB 4G7 MoAb, ΨL cell surface expression was detected on normal bone marrow, not only on CD34−CD19+ preB but also on CD34+CD19+ proB cells. Futhermore, this MoAb identified ΨL+μ− fresh proB leukemic cells of the TEL/AML1 type. Biochemical studies showed that, at the proB stage, the ΨL is associated noncovalently with two proteins of 105 and 130 kD. Triggering of this complex induces intracellular Ca2+ flux, suggesting that the ΨL may be involved in a new receptor at this early step of the B-cell differentiation.
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