The CD19/CD21 signal transduction complex of B lymphocytes

Clinical analysis of immune reconstitution after chemotherapy in children with acute lymphoblastic leukemia

OBJECTIVES

The aim of this retrospective study was to investigate the influence of chemotherapy on the immune status of individual patients diagnosed with acute lymphoblastic leukemia (ALL) and to elucidate the clinical characteristics of immune reconstitution in ALL patients following chemotherapy.

METHODS

Clinical data of children with ALL were gathered, including information on the number of lymphocyte subsets prior to chemotherapy, at the end of therapy, six months, and one year after the end of the treatment.

RESULTS

A total of 146 children with ALL were included, and T cells, B cells, and NK cells all decreased to various degrees prior to treatment. The abnormal CD3 + T cell numbers group experienced a considerably higher mortality (21.9% vs. 6.1%) and recurrence rate (31.3% vs. 11.4%) compared to the normal group (P < 0.05). T cells, B cells, and NK cells were all significantly compromised at the end of therapy compared to the beginning of chemotherapy, with B cells being more severely compromised (P < 0.001). At the end of treatment, levels of B cells, CD4 + T cells, CD4/CD8, IgG and IgM in low risk (LR) group were significantly higher than those in intermediate risk (IR) group (P < 0.01), and levels of NK cells in LR group were evidently lower than those in IR group (P < 0.001). Six months after the end of therapy, all the above indicators recovered (P < 0.001) except CD4/CD8 ratio (P = 0.451).

CONCLUSIONS

The immune systems of the ALL patients were severely compromised upon therapy withdrawal, particularly the B cells. At six months after the therapy ended, the B cells were basically restored to normal level, while the T-cell compartment was not. The impaired numbers of CD3 + T cell may contribute to a weakened anti-tumor response, potentially leading to a poorer prognosis.

Optimization of preparation method and specificity verification of cat CD19 monoclonal antibody for disease diagnosis and treatment

CD19 is a surface antigen on B cells that regulates B cell activation and proliferation, participating in B cell signaling. It is expressed in all B cell lineage tumor diseases, making CD19 a significant marker for detecting B cell tumor diseases and an important target for related immunotherapies. In recent years, with the deepening research on canine and feline diseases and the establishment of animal models, the demand for cat CD19 monoclonal antibodies (mAbs) has been steadily increasing. We successfully prepared cat CD19-specific monoclonal antibodies using a KLH-conjugated cat CD19 peptide as an antigen and optimized the antibody production method. The obtained monoclonal antibodies' molecular and cellular affinities were identified using CD19 peptides, eukaryotic overexpressed proteins, and peripheral blood mononuclear cells (PBMCs). The results indicate that the CD19-3H9 and CD19-8A7 monoclonal antibodies prepared in this study specifically bind to the CD19 molecule, demonstrating their suitability for use in ELISA, Western blot, and cell assays. This study successfully produced cat CD19 monoclonal antibodies with specificity and optimized the antibody preparation method, laying the foundation for the diagnosis and targeted drug combination therapy of B cell tumor diseases in both humans and pets.

Immune cell early activation, apoptotic kinetic, and T-cell functional impairment in domestic pigs after ASFV CADC_HN09 strain infection

African swine fever (ASF) caused by the African swine fever virus (ASFV) is a fatal and highly contagious disease of domestic pigs characterized by rapid disease progression and death within 2 weeks. How the immune cells respond to acute ASFV infection and contribute to the immunopathogenesis of ASFV has not been completely understood. In this study, we examined the activation, apoptosis, and functional changes of distinct immune cells in domestic pigs following acute infection with the ASFV CADC_HN09 strain using multicolor flow cytometry. We found that ASFV infection induced broad apoptosis of DCs, monocytes, neutrophils, and lymphocytes in the peripheral blood of pigs over time. The expression of MHC class II molecule (SLA-DR/DQ) on monocytes and conventional DCs as well as CD21 expression on B cells were downregulated after ASFV infection, implying a potential impairment of antigen presentation and humoral response. Further examination of CD69 and ex vivo expression of IFN-γ on immune cells showed that T cells were transiently activated and expressed IFN-γ as early as 5 days post-infection. However, the capability of T cells to produce cytokines was significantly impaired in the infected pigs when stimulated with mitogen. These results suggest that the adaptive cellular immunity to ASFV might be initiated but later overridden by ASFV-induced immunosuppression. Our study clarified the cell types that were affected by ASFV infection and contributed to lymphopenia, improving our understanding of the immunopathogenesis of ASFV.

Ocrelizumab associates with reduced cerebrospinal fluid B and CD20dim CD4+ T cells in primary progressive multiple sclerosis

The anti-CD20 monoclonal antibody ocrelizumab reduces disability progression in primary progressive multiple sclerosis. CD20 is a prototypical B-cell marker; however, subpopulations of CD4+ and CD8+ T cells in peripheral blood and cerebrospinal fluid also express low levels of CD20 (CD20dim). Therefore, direct targeting and depletion of these CD20dim T-cell subpopulations may contribute to the therapeutic effect of ocrelizumab. The aim of this observational cohort study was to compare CD20+ B-cell and CD20dim T-cell distributions between peripheral blood and cerebrospinal fluid of ocrelizumab-treated or ocrelizumab-untreated people with primary progressive multiple sclerosis. Ocrelizumab treatment was associated with depletion of circulating B cells and CD20dim CD4+ and CD20dim CD8+ T cells (P < 0.0001, P = 0.0016 and P = 0.0008, respectively) but, in cerebrospinal fluid, only with lower proportions of B cells and CD20dim memory CD4+ T cells (P < 0.0001 and P = 0.0043, respectively). The proportional prevalence of cerebrospinal fluid CD20dim memory CD8+ T cells was not significantly reduced (P = 0.1333). Only in cerebrospinal fluid, the proportions of CD20dim cells within CD4+ and not CD8+ T cells positive for CCR5, CCR6 and CXCR3 were reduced in ocrelizumab-treated participants. The proportion of CD20dim CD4+ T cells and abundance of CD4+ relative to CD8+ T cells in cerebrospinal fluid correlated positively with age (R = 0.6799, P = 0.0150) and Age-Related Multiple Sclerosis Severity score (R = 0.8087, P = 0.0014), respectively. We conclude that, in contrast to cerebrospinal fluid CD20dim CD8+ T cells, B cells and CD20dim CD4+ T cells are reduced in cerebrospinal fluid of people with primary progressive multiple sclerosis with an ocrelizumab-associated depletion of circulating B cells and CD20dim T cells. Therefore, these cells are likely to contribute to the therapeutic effects of ocrelizumab in people with primary progressive multiple sclerosis.

Targeting CD19 for diffuse large B cell lymphoma in the era of CARs: Other modes of transportation

CD19 is nearly ubiquitously expressed on B-lymphocytes and in B-cell malignancies. Although CD19-directed CAR T cells have greatly improved outcomes in B-cell malignancies, there are significant limitations with this therapy. CD19 can also be effectively targeted by other drug classes, such as monoclonal antibodies, antibody-drug conjugates, and bispecific T cell engagers or antibodies. However, the optimal patient selection and sequencing of these novel therapies has not yet been established. In this review, we discuss the utilization of CD19 as a target for the treatment of DLBCL, focusing on tafasitamab, loncastuximab tesirine, and blinatumomab. We provide a comprehensive review of the pivotal clinical trials, discussing the strength and limitations of the data for each agent. We explore the emerging evidence that CD19 expression is retained following exposure to these agents and that patients can be successfully re-challenged with anti-CD19 therapies of a different drug class upon disease relapse post-CAR T cells. Finally, we discuss how these drugs potentially fit into the most current treatment paradigm for DLBCL.

Efficacy and safety of CD19 CAR-T cell therapy for acute lymphoblastic leukemia patients relapsed after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective therapy for B-cell acute lymphoblastic leukemia (B-ALL). Although allo-HSCT can be curative for some B-ALL patients, relapse still occurs in some patients following allo-HSCT. Conventional chemotherapies show poor efficacy in B-ALL patients who have relapsed following allo-HSCT. In the past decade, chimeric antigen receptor T-cell (CAR-T) therapy has shown to be efficacious for B-ALL patients. In particular, autologous CD19 CAR-T therapy results in a high remission rate. However, there are challenges in the use of CD19 CAR-T therapy for B-ALL patients who have relapsed following allo-HSCT, including the selection of CAR-T cell source for manufacturing, post-CAR-T graft-versus-host disease (GVHD) risk, maintenance of long-term efficacy after remission through CAR-T therapy, and whether a consolidative second transplant is needed. In this review, we describe the current status of CAR-T therapy for B-ALL patients who have relapsed following allo-HSCT, the advantages and disadvantages of various CAR-T cell sources, the characteristics and management of GVHD following CAR-T therapy, and the risk factors that may affect long-term efficacy.

Bispecific Antibody-Based Immune-Cell Engagers and Their Emerging Therapeutic Targets in Cancer Immunotherapy

Cancer is the second leading cause of death worldwide after cardiovascular diseases. Harnessing the power of immune cells is a promising strategy to improve the antitumor effect of cancer immunotherapy. Recent progress in recombinant DNA technology and antibody engineering has ushered in a new era of bispecific antibody (bsAb)-based immune-cell engagers (ICEs), including T- and natural-killer-cell engagers. Since the first approval of blinatumomab by the United States Food and Drug Administration (US FDA), various bsAb-based ICEs have been developed for the effective treatment of patients with cancer. Simultaneously, several potential therapeutic targets of bsAb-based ICEs have been identified in various cancers. Therefore, this review focused on not only highlighting the action mechanism, design and structure, and status of bsAb-based ICEs in clinical development and their approval by the US FDA for human malignancy treatment, but also on summarizing the currently known and emerging therapeutic targets in cancer. This review provides insights into practical considerations for developing next-generation ICEs.

Role of Globotriaosylceramide in Physiology and Pathology

At first glance, the biological function of globoside (Gb) clusters appears to be that of glycosphingolipid (GSL) receptors for bacterial toxins that mediate host-pathogen interaction. Indeed, certain bacterial toxin families have been evolutionarily arranged so that they can enter eukaryotic cells through GSL receptors. A closer look reveals this molecular arrangement allocated on a variety of eukaryotic cell membranes, with its role revolving around physiological regulation and pathological processes. What makes Gb such a ubiquitous functional arrangement? Perhaps its peculiarity is underpinned by the molecular structure itself, the nature of Gb-bound ligands, or the intracellular trafficking unleashed by those ligands. Moreover, Gb biological conspicuousness may not lie on intrinsic properties or on its enzymatic synthesis/degradation pathways. The present review traverses these biological aspects, focusing mainly on globotriaosylceramide (Gb3), a GSL molecule present in cell membranes of distinct cell types, and proposes a wrap-up discussion with a phylogenetic view and the physiological and pathological functional alternatives.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Developmental partitioning of SYK and ZAP70 prevents autoimmunity and cancer

Even though SYK and ZAP70 kinases share high sequence homology and serve analogous functions, their expression in B and T cells is strictly segregated throughout evolution. Here, we identified aberrant ZAP70 expression as a common feature in a broad range of B cell malignancies. We validated SYK as the kinase that sets the thresholds for negative selection of autoreactive and premalignant clones. When aberrantly expressed in B cells, ZAP70 competes with SYK at the BCR signalosome and redirects SYK from negative selection to tonic PI3K signaling, thereby promoting B cell survival. In genetic mouse models for B-ALL and B-CLL, conditional expression of Zap70 accelerated disease onset, while genetic deletion impaired malignant transformation. Inducible activation of Zap70 during B cell development compromised negative selection of autoreactive B cells, resulting in pervasive autoantibody production. Strict segregation of the two kinases is critical for normal B cell selection and represents a central safeguard against the development of autoimmune disease and B cell malignancies.

Anti-CD19 CAR T cells potently redirected to kill solid tumor cells

Successful CAR T cell therapy for the treatment of solid tumors requires exemplary CAR T cell expansion, persistence and fitness, and the ability to target tumor antigens safely. Here we address this constellation of critical attributes for successful cellular therapy by using integrated technologies that simplify development and derisk clinical translation. We have developed a CAR-CD19 T cell that secretes a CD19-anti-Her2 bridging protein. This cell therapy strategy exploits the ability of CD19-targeting CAR T cells to interact with CD19 on normal B cells to drive expansion, persistence and fitness. The secreted bridging protein potently binds to Her2-positive tumor cells, mediating CAR-CD19 T cell cytotoxicity in vitro and in vivo. Because of its short half-life, the secreted bridging protein will selectively accumulate at the site of highest antigen expression, ie. at the tumor. Bridging proteins that bind to multiple different tumor antigens have been created. Therefore, antigen-bridging CAR-CD19 T cells incorporate critical attributes for successful solid tumor cell therapy. This platform can be exploited to attack tumor antigens on any cancer.

A Review of Clinical Outcomes of CAR T-Cell Therapies for B-Acute Lymphoblastic Leukemia

Introduction: Treatment of relapsed and refractory (R/R) B acute lymphoblastic leukemia (B-ALL) represents an unmet medical need in children and adults. Adoptive T cells engineered to express a chimeric antigen receptor (CAR-T) is emerging as an effective technique for treating these patients. Areas covered: Efficacy and safety of CAR-T therapy in R/R B-ALL patients. Expert opinion: CD19 CAR-T infusion induce high CR rates in patients with poor prognosis and few therapeutic options, while real-life data demonstrate similar results with an interestingly lower incidence of grade 3/4 toxicity. Nevertheless, despite impressive in-depth responses, more than half of patients will experience a relapse. Therefore, rather than using CAR-T cell therapy as a stand-alone option, consolidation with allogeneic stem-cell transplant (Allo-SCT) after CAR-T treatment might increase long-term outcome. Moreover, CD19 is one target, but several other targets are being examined, such as CD20 and CD22 and dual-targeting CARs or combination therapy. Another issue is the time consuming process of CAR-T engineering. New platforms have shortened the CAR-T cell manufacturing process, and studies are underway to evaluate the effectiveness. Another way to mitigate waiting is the development of allogeneic “off the shelf” therapy. In conclusion, CD19-targeted CAR-modified T-cell therapy has shown unprecedented results in patients without curative options. Future work focusing on target identification, toxicity management and reducing manufacturing time will broaden the clinical applicability and bring this exciting therapy to more patients, with longer-term remissions without additional Allo-SCT.

Challenges and Clinical Strategies of CAR T-Cell Therapy for Acute Lymphoblastic Leukemia: Overview and Developments

Chimeric antigen receptor (CAR) T-cell therapy exhibits desirable and robust efficacy in patients with acute lymphoblastic leukemia (ALL). Stimulated by the revolutionized progress in the use of FDA-approved CD19 CAR T cells, novel agents with CAR designs and targets are being produced in pursuit of superior performance. However, on the path from bench to bedside, new challenges emerge. Accessibility is considered the initial barrier to the transformation of this patient-specific product into a commercially available product. To ensure infusion safety, profound comprehension of adverse events and proactive intervention are required. Additionally, resistance and relapse are the most critical and intractable issues in CAR T-cell therapy for ALL, thus precluding its further development. Understanding the limitations through up-to-date insights and characterizing multiple strategies will be critical to leverage CAR T-cell therapy flexibly for use in clinical situations. Herein, we provide an overview of the application of CAR T-cell therapy in ALL, emphasizing the main challenges and potential clinical strategies in an effort to promote a standardized set of treatment paradigms for ALL.

Tetraspanin Scaffold Proteins Function as Key Regulators of Hematopoietic Stem Cells

Hematopoietic stem and progenitor cells (HSPCs) are responsible for the development, maintenance, and regeneration of all the blood forming cells in the body, and as such, are critical for a number of patient therapies. For successful HSPC transplantation, stem cells must traffic through the blood and home to the bone marrow (BM) microenvironment or “niche,” which is composed of soluble factors, matrix proteins, and supportive cells. HSPC adhesion to, and signaling with, cellular and extracellular components of the niche provide instructional cues to balance stem cell self-renewal and differentiation. In this review, we will explore the regulation of these stem cell properties with a focus on the tetraspanin family of membrane proteins. Tetraspanins are molecular scaffolds that uniquely function to distribute proteins into highly organized microdomains comprising adhesion, signaling, and adaptor proteins. As such, tetraspanins contribute to many aspects of cell physiology as mediators of cell adhesion, trafficking, and signaling. We will summarize the many reports that identify tetraspanins as markers of specific HSPC populations. Moreover, we will discuss the various studies establishing the functional importance of tetraspanins in the regulation of essential HSPC processes including quiescence, migration, and niche adhesion. When taken together, studies outlined in this review suggest that several tetraspanins may serve as potential targets to modulate HSPC interactions with the BM niche, ultimately impacting future HSPC therapies.

Adoptive Immunotherapy for B-cell Malignancies Using CD19- Targeted Chimeric Antigen Receptor T-Cells: A Systematic Review of Efficacy and Safety

BACKGROUND

Adoptive infusion of chimeric antigen receptor transduced T- cells (CAR-T) is a powerful tool of immunotherapy for hematological malignancies, as evidenced by recently published and unpublished clinical results.

OBJECTIVE

In this report, we performed a meta-analysis to evaluate the efficacy and side effects of CAR-T on refractory and/or relapsed B-cell malignancies, including leukemia and lymphoma.

METHODS

Clinical studies investigating efficacy and safety of CAR-T in acute and chronic lymphocytic leukemia and lymphoma were identified by searching PubMed and EMBASE. Outcomes of efficacy subjected to analysis were the rates of complete remission (CR) and partial remission (PR). The safety parameters were the prevalence of adverse effects including fever, hypotension, and acute renal failure. Meta analyses were performed using R software. Weighted hazard ratio (HR) with 95% confidence intervals was calculated for each outcome. Fixed or random-effects models were employed depending on the heterogeneity across the included studies.

RESULTS

Nineteen published clinical studies with a total of 391 patients were included for the meta-analysis. The pooled rate of complete remission was 55% (95% CI 41%-69%); the pooled rate of partial remission was 25% (95% CI: 19%-33%). The prevalence of fever was 62% (95% CI: 41%-79%), the hypotension was 22% (95% CI: 15%-31%), and the acute renal failure was 24% (95% CI: 16%-34%). All adverse effects were manageable and no death was reported due to toxicity.

CONCLUSION

CD19-targeted CAR-T is an effective modality in treating refractory B-cell malignancies including leukemia and lymphoma. However, there is still a need to develop strategies to improve the safety in its clinical use.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Fc receptor-like 1 intrinsically recruits c-Abl to enhance B cell activation and function

B cell activation is regulated by the stimulatory or inhibitory co-receptors of B cell receptors (BCRs). Here, we investigated the signaling mechanism of Fc receptor-like 1 (FcRL1), a newly identified BCR co-receptor. FcRL1 was passively recruited into B cell immunological synapses upon BCR engagement in the absence of FcRL1 cross-linking, suggesting that FcRL1 may intrinsically regulate B cell activation and function. BCR cross-linking alone led to the phosphorylation of the intracellular Y281ENV motif of FcRL1 to provide a docking site for c-Abl, an SH2 domain-containing kinase. The FcRL1 and c-Abl signaling module, in turn, potently augmented B cell activation and proliferation. FcRL1-deficient mice exhibited markedly impaired formation of extrafollicular plasmablasts and germinal centers, along with decreased antibody production upon antigen stimulation. These findings reveal a critical BCR signal-enhancing function of FcRL1 through its intrinsic recruitment to B cell immunological synapses and subsequent recruitment of c-Abl upon BCR cross-linking.

Immune network for viral hepatitis B: Topological representation

The liver is a well-known immunotolerogenic environment, which provides the adequate setting for liver infectious pathogens persistence such as the hepatitis B virus (HBV). Consequently, HBV infection can derive in the development of chronic disease in a proportion of the patients. If this situation persists in time, chronic hepatitis B (CHB) would end in cirrhosis, hepatocellular carcinoma and eventually, the death of the patient. It is thought that this immunotolerogenic environment is the result of complex interactions between different elements of the immune system and the viral biology. Therefore, the purpose of this work is to unravel the mechanisms implied in the development of CHB and to design a tool able to help in the study of adequate therapies. Firstly, a conceptual framework with the main components of the immune system and viral dynamics was constructed providing an overall insight on the pathways and interactions implied in this disease. Secondly, a review of the literature was performed in a modular fashion: (i) viral dynamics, (ii) innate immune response, (iii) humoral and (iv) cellular adaptive immune responses and (v) tolerogenic aspects. Finally, the information collected was integrated into a single topological representation that could serve as the plan for the systems pharmacology model architecture. This representation can be considered as the previous unavoidable step to the construction of a quantitative model that could assist in biomarker and target identification, drug design and development, dosing optimization and disease progression analysis.

CTL019 (tisagenlecleucel): CAR-T therapy for relapsed and refractory B-cell acute lymphoblastic leukemia

Over the past decades, survival of patients with acute lymphoblastic leukemia (ALL) has dramatically improved, but the subgroup of patients with relapsed/refractory ALL still continues to have dismal prognosis. As an emerging therapeutic approach, chimeric antigen receptor-modified T-cells (CAR-T) represent one of the few practice-changing therapies for this subgroup of patients. Originally conceived and built in Philadelphia (University of Pennsylvania), CTL019 or tisagenlecleucel, the first CAR-T approved by the US Food and Drug Administration, showed impressive results in refractory/relapsed ALL since the publication on two pediatric patients in 2013. It is in this context that we provide a review of this product in terms of manufacturing, pharmacology, toxicity, and efficacy studies. Evaluation and management of toxicities, particularly cytokine release syndrome and neurotoxicity, is recognized as an essential part of the patient treatment with broader use of IL-6 receptor inhibitor. An under-assessed aspect, the quality of life of patients entering CAR-T cells treatment, will also be reviewed. By their unique nature, CAR-T cells such as tisagenlecleucel operate in a different way than typical drugs, but also provide unique hope for B-cell malignancies.

The levels of soluble forms of CD21 and CD83 in multiple sclerosis

Multiple Sclerosis (MS) is a neuroinflammatory disease of the central nervous system (CNS) in which immune system plays a crucial role in progression of the disease. An enormous amount of research has been shown that immune mediators such as cytokines and chemokines are the culprits of MS propagation suggesting that modulation of such molecules may pave the path to hinder the disease development. It has been shown that both CD21 and CD83 contribute to the resolution of inflammation occurred in MS. CD21 and CD83 have also been ascribed to Epstein Barr virus (EBV) infection (the prime suspect of MS causality) and the levels of vitamin D, respectively. Hence, in this study, we measured the serum concentrations of soluble forms of CD21 and CD83 in 255 patients with MS divided into two groups who were receiving interferon-beta (185 MS patients) and fingolimod (70 MS patients) in comparison to 384 healthy individuals. The levels of EBV titers including anti-VCA IgM, anti-VCA IgG and anti-EBNA-1 IgG were also measured. The results showed that the concentration of soluble CD21 (sCD21) was markedly decreased in serum samples of MS patients with respect of controls. Contrarily, the level of soluble CD83 (sCD83) was elevated in MS patients compared to healthy individuals. In addition, the levels of sCD21 and sCD83 were correlated with the titers of EBV. The data showed the significant association between the expanded disability status scale (EDSS) and the levels of both sCD21 and sCD83. It seems that both sCD21 and sCD83 might be good candidate for disease monitoring and can be considered potential biomarkers for the disease activity.

The role of the mitochondria and the endoplasmic reticulum contact sites in the development of the immune responses

Mitochondria and endoplasmic reticulum (ER) contact sites (MERCs) are dynamic modules enriched in subset of lipids and specialized proteins that determine their structure and functions. The MERCs regulate lipid transfer, autophagosome formation, mitochondrial fission, Ca2+ homeostasis and apoptosis. Since these functions are essential for cell biology, it is therefore not surprising that MERCs also play a critical role in organ physiology among which the immune system stands by its critical host defense function. This defense system must discriminate and tolerate host cells and beneficial commensal microorganisms while eliminating pathogenic ones in order to preserve normal homeostasis. To meet this goal, the immune system has two lines of defense. First, the fast acting but unspecific innate immune system relies on anatomical physical barriers and subsets of hematopoietically derived cells expressing germline-encoded receptors called pattern recognition receptors (PRR) recognizing conserved motifs on the pathogens. Second, the slower but very specific adaptive immune response is added to complement innate immunity. Adaptive immunity relies on another set of specialized cells, the lymphocytes, harboring receptors requiring somatic recombination to be expressed. Both innate and adaptive immune cells must be activated to phagocytose and process pathogens, migrate, proliferate, release soluble factors and destroy infected cells. Some of these functions are strongly dependent on lipid transfer, autophagosome formation, mitochondrial fission, and Ca2+ flux; this indicates that MERCs could regulate immunity.

Pathogenic roles of B lymphocytes in systemic sclerosis

Systemic sclerosis (SSc) is a collagen disease characterized by autoimmunity and excessive extracellular matrix deposition in the skin and visceral organs. Although the pathogenic relationship between systemic autoimmunity and the clinical manifestations of SSc remains unknown, SSc patients show a variety of abnormal immune activation including the production of disease-specific autoantibodies and cytokine production. Many recent studies have demonstrated that immune cells, including T cells, B cells, and macrophages, have a variety of immunological abnormalities in SSc. So far, several groups and our group reported that B cells play a critical role in systemic autoimmunity and disease expression through various functions, such as cytokine production, lymphoid organogenesis, and induction of other immune cell activation in addition to autoantibody production. Recent studies show that B cells from SSc patients demonstrate an up-regulated CD19 expression, a crucial regulator of B cell activation, which induces chronic hyper-reactivity of memory B cells and SSc-specific autoantibody production and also causes fibrosis of several organs. Furthermore, in SSc-model mice, such as tight-skin mice, bleomycin-induced SSc model mice, and DNA topoisomerase I and complete Freund's adjuvant-induced SSc model mice, have abnormal B cell activation which associates with skin and lung fibrosis. Indeed, B cell depletion therapy using anti-CD20 Ab, Rituximab, is considered to one potential beneficial treatment for patients with SSc. However, there is no direct evidence which can explain how B cells, especially autoantigen-reactive B cells, progress or regulate disease manifestations of SSc. Collectively, B cell abnormalities in SSc is most likely participating in fibrosis and tissue damage of SSc. If the relationship between SSc-specific tissue damage and B cell abnormalities is revealed, these findings lead to novel effective therapy for SSc.

Promises and limitations of nanoparticles in the era of cell therapy: Example with CD19-targeting chimeric antigen receptor (CAR)-modified T cells

A number of nanoparticles has been developed by chemists for biomedical applications to meet imaging and targeting needs. In parallel, adoptive T therapy with chimeric antigen receptor engineered T cells (CART cells) has recently held great promise in B-cell malignancy treatments thanks to the development of anti-CD19 CAR T cells. Indeed, CD19 is a reliable B cell marker and a validated target protein for therapy. In this perspective article, we propose to discuss the advantages, limits and challenges of nanoparticles and CAR T cells, focusing on CD19 targeting objects: anti-CD19 nanoparticles and anti-CD19 CAR T cells, because those genetically-modified cells are the most widely developed in clinical setting. In the first part, we will introduce B cell malignancies and the CD19 surface marker. Then we will present the positioning of nanomedicine in the topic of B cell malignancy, before exposing CAR T technology. Finally, we will discuss the complementary approaches between nanoparticles and CAR T cells.

A lifetime aging study of human CD19 transgenic mice

Mice transgenic for human CD19 have been an important animal model to help understand the role of this molecule in B lymphocyte function. Previously, no lifetime studies had been performed to understand the effects of this CD19 over expression on the survival or spontaneous pathology within the C57BL/6J background strain. We conducted a lifetime study with interim sacrifices to understand the transgenic effects on clinical signs, body weight, survival, and spontaneous pathology. Blood and urine samples were collected from select animals at various time points during the study for measurement of clinical pathology parameters and groups of animals were euthanized and examined at predetermined intervals. There was fair survival with some animals living to 108 weeks of age. Clinical pathology evaluations revealed a declining red cell mass with a regenerative anemia, increasing total white blood cell counts and decreasing glucose level. Total protein, albumin, and globulin levels increased to 52 weeks of age and then declined to or below baseline with advancing age. Increased urinary microalbumin levels correlated with the severity of a glomerulopathy at 76 and 84 weeks of age. Mean body weight increased through 70 weeks and then declined to weights similar to week 28 at 108 weeks. Macroscopic observations included pale kidneys, enlarged seminal vesicles, and enlarged spleens (at 108 weeks of age). The most common neoplasms in this study were bronchiolar alveolar adenomas in the lung, histiocytic sarcoma in several different tissues, and hepatocellular adenomas. The most common non-neoplastic lesions were renal glomerulopathy, and pulmonary lymphocytic infiltrates with increased numbers of alveolar macrophages.

B lymphocytes in systemic sclerosis: Abnormalities and therapeutic targets

Systemic sclerosis (SSc) is a connective tissue disease characterized by excessive extracellular matrix deposition in the skin and visceral organs with an autoimmune background. Although the pathogenic relationship between systemic autoimmunity and the clinical manifestations remains unknown, SSc patients have immunological abnormalities including the production of disease-specific autoantibodies. Recent studies have demonstrated that B cells play a crucial role in systemic autoimmunity and disease expression via various functions in addition to autoantibody production. Recent studies show that B cells from SSc patients demonstrate an upregulated CD19 signaling pathway, which is a crucial regulator of B-cell activation, that induces SSc-specific autoantibody production in SSc. In addition, B cells from SSc patients exhibit an overexpression of CD19. Consistently, in CD19 transgenic mice, CD19 overexpression induces SSc-specific autoantibody production. SSc patients have also intrinsic B-cell abnormalities characterized by chronic hyperreactivity of memory B cells, possibly due to CD19 overexpression. Similarly, B cells from a tight-skin mouse, a genetic model of SSc, show augmented CD19 signaling and chronic hyperreactivity. Furthermore, in bleomycin-induced SSc model mice, endogenous ligands for Toll-like receptors, induced by bleomycin treatment, stimulate B cells to produce various fibrogenic cytokines and autoantibodies. Remarkably, CD19 loss results in inhibition of B-cell hyperreactivity and elimination of autoantibody production, which is associated with improvement of fibrosis. Taken together, altered B-cell function may result in tissue fibrosis, as well as autoimmunity, in SSc. Although further studies and greater understanding are needed, B cells are potential therapeutic target in SSc.

5'UTR +24T>C CR2 is not associated with nasopharyngeal carcinoma development in the North Region of Portugal

OBJECTIVE

We have analysed the association of the +24T>C polymorphism (rs3813946) in CR2, the cellular receptor for Epstein-Barr virus (EBV), in the susceptibility for the development of nasopharyngeal carcinoma (NPC).

METHODS

A retrospective case-control study was developed with peripheral blood samples from 111 individuals with NPC and 608 healthy individuals (controls) from the North region of Portugal. The genotyping analysis was performed by allelic discrimination real-time PCR using a TaqMan(®) SNP Genotyping Assay.

RESULTS

The genotype distribution was 62.2% TT, 34.2% TC and 3.6% CC for NPC patients; and 65.0%, 30.6% and 4.4%, respectively, for controls. Our study showed no statistical association between the genotype distribution in controls and all types of NPC (P = 0.717); nevertheless, the analysis showed statistically significant differences (P = 0.038) regarding cases with well- or moderately differentiated types of NPC suggesting that +24CC/CT genotypes are associated with increased risk (OR = 4.16; 95% CI 1.28-15.7; P = 0.016).

CONCLUSIONS

This is the first study in Western populations to characterize the association of the CR2 +24T>C polymorphism in NPC development, and our results suggest that more studies are required to clarify the impact on NPC susceptibility in different populations.

Pre-stimulation of CD81 expression by resting B cells increases proliferation following EBV infection, but the overexpression of CD81 induces the apoptosis of EBV-transformed B cells

Hepatitis C virus (HCV) E2 protein binds to CD81, which is a component of the B cell co-stimulatory complex. The E2-CD81 interaction leads to B cell proliferation, protein tyrosine phosphorylation and to the hypermutation of immunoglobulin genes. Epidemiological studies have reported a high prevalence of B cell non-Hodgkin lymphoma (NHL) in HCV-positive patients, suggesting a potential association between HCV and Epstein-Barr virus (EBV) in the genesis of B lymphocyte proliferative disorders. In the present study, in order to investigate the association between EBV and HCV in B cells, we created an in vitro EBV-induced B cell transformation model. CD81 was gradually overexpressed during transformation by EBV. B cells isolated from HCV-positive patients grew more rapidly and clumped together earlier than B cells isolated from healthy donors following EBV infection. Pre-stimulation of CD81 expressed by resting B cells with anti-CD81 monoclonal antibody (mAb) or HCV E2 accelerated the generation of lymphoblastoid cell lines (LCLs) by EBV infection. These cells proliferated prominently through the early expression of interleukin-10 and intracellular latent membrane protein (LMP)-l. By contrast, the overexpression of CD81 on EBV-transformed B cells by anti-CD81 mAb or HCV E2 protein induced apoptosis through reactive oxygen species (ROS)-mediated mitochondrial dysfunction. These results suggest that the engagement of CD81 expressed by B cells has differential effects on B cell fate (proliferation or apoptosis) according to EBV infection and the expression level of CD81.

Lymphoid lineage differentiation potential of mouse nuclear transfer embryonic stem cells

Stem cells therapy is considered as an efficient strategy for the treatment of some diseases. Nevertheless, some obstacles such as probability of rejection by the immune system limit applications of this strategy. Therefore, several efforts have been made to overcome this among which using the induced pluripotent stem cells (iPSCs) and nuclear transfer embryonic stem cell (nt-ESCs) are the most efficient strategies. The objective of this study was to evaluate the differentiation potential of the nt-ESCs to lymphoid lineage in the presence of IL-7, IL-3, FLT3-ligand and TPO growth factors in vitro. To this end, the nt-ESCs cells were prepared and treated with aforementioned growth factors for 7 and 14 days. Then, the cells were examined for expression of lymphoid markers (CD3, CD25, CD127 and CD19) by quantitative PCR (q-PCR) and flow cytometry. An increased expression of CD19 and CD25 markers was observed in the treated cells compared with the negative control samples by day 7. After 14 days, the expression level of all the tested CD markers significantly increased in the treated groups in comparison with the control. The current study reveals the potential of the nt-ESCs in differentiation to lymphoid lineage in the presence of defined growth factors.

A new mouse anti-mouse complement receptor type 2 and 1 (CR2/CR1) monoclonal antibody as a tool to study receptor involvement in chronic models of immune responses and disease

Although reagents are available to block mouse complement receptor type 2 and/or type 1 (CR2/CR1, CD21/CD35) function in acute or short term models of human disease, a mouse anti-rat antibody response limits their use in chronic models. We have addressed this problem by generating in Cr2−/− mice a mouse monoclonal antibody (mAb 4B2) to mouse CR2/CR1. The binding of murine mAb 4B2 to CR2/CR1 directly blocked C3dg (C3d) ligand binding. In vivo injection of mAb 4B2 induced substantial down regulation of CR2 and CR1 from the B cell surface, an effect that lasted six weeks after a single injection of 2 mg of mAb. The 4B2 mAb was studied in vivo for the capability to affect immunological responses to model antigens. Pre-injection of mAb 4B2 before immunization of C57BL/6 mice reduced the IgG1 antibody response to the T-dependent antigen sheep red blood cells (SRBC) to a level comparable to that found in Cr2−/− mice. We also used the collagen-induced arthritis (CIA) model, a CR2/CR1-dependent autoimmune disease model, and found that mice pre-injected with mAb 4B2 demonstrated substantially reduced levels of pathogenic IgG2a antibodies to both the bovine type II collagen (CII) used to induce arthritis and to endogenous mouse CII. Consistent with this result, mice pre-injected with mAb 4B2 demonstrated only very mild arthritis. This reduction in disease, together with published data in CII-immunized Cr2−/− mice, confirm both that the arthritis development depends on CR2/CR1 receptors and that mAb 4B2 can be used to induce biologically relevant receptor blockade. Thus mAb 4B2 is an excellent candidate for use in chronic murine models to determine how receptor blockage at different points modifies disease activity and autoantibody responses.

Abnormal B lymphocyte activation and function in systemic sclerosis

Systemic sclerosis (SSc) is characterized by tissue fibrosis and autoimmunity. Although the pathogenic relationship between autoimmunity and clinical manifestations of SSc remains unknown, SSc patients display abnormal immune responses including the production of disease-specific autoantibodies. Previous studies have demonstrated that B cells play a critical role in systemic autoimmunity and disease expression through various functions such as induction of the activation of other immune cells in addition to autoantibody production. CD19 is a crucial regulator of B cell activation. Recent studies demonstrated that B cells from SSc patients showed an up-regulated CD19 signaling pathway that induced SSc-specific autoantibody production in SSc mouse models. CD19 transgenic mice lost tolerance for autoantigen and generated autoantibodies spontaneously. B cells from SSc patients exhibited an overexpression of CD19 that induced SSc-specific autoantibody production in transgenic mice. Moreover, SSc patients displayed intrinsic B cell abnormalities characterized by chronic hyper-reactivity of memory B cells, which was possibly due to CD19 overexpression. Similarly, B cells from a tight-skin mouse, a genetic model of SSc, showed augmented CD19 signaling. In bleomycin-induced SSc mouse models, endogenous ligands for toll-like receptor 4 induced by bleomycin stimulated B cells to produce various fibrogenic cytokines and autoantibodies. Remarkably, the loss of CD19 resulted in the inhibition of B cell hyper-reactivity and autoantibody production, which are associated with improvements in fibrosis and a parallel decrease in fibrogenic cytokine production by B cells. Taken together, the findings suggest that altered B cell function may result in tissue fibrosis as well as autoimmunity in SSc.

Chemical synthesis, cytotoxicity, selectivity and bioavailability of 5α-androstane-3α,17β-diol derivatives

Aminosteroid derivatives represent a new family of compounds with promising antiproliferative activity over different cancer cell lines. Among all the aminosteroid derivatives synthesised in our laboratory, we have identified E-37P as one of the more potent when tested in vitro. Unfortunately, the pharmacokinetic properties of E-37P decrease its effectiveness when tested in vivo. To improve the bioavailability and increase the efficiency of aminosteroid E-37P, two series of analog compounds were synthesised by classic chemical synthesis, they were then characterized, and the concentration that inhibits 50% of cell proliferation (IC50) was determined on different cell lines. RM-133, a 5α-androstane-3α,17β-diol derivative with a quinoline nucleus at the end of the piperazine-proline side-chain at position 2β and an ethinyl at position 17α, showed very good antiproliferative activity among the five cancer cell lines studied (IC50=0.1, 0.1, 0.1, 2.0 and 1.1 μM for HL-60, MCF-7, T-47D, LNCaP and WEHI-3, respectively). Moreover, the plasmatic concentration of RM-133 at 3h, when injected subcutaneously in rats, was 2.3-fold higher than that of E-37P (151 vs 64.8 ng/mL). Furthermore, RM-133 weakly inhibited the two representative liver enzymes, CYP3A4 and CYP2D6, indicating a very low risk of drug-drug interactions. The cytotoxicity of RM-133 against normal cells was tested on peripheral blood lymphocytes (PBL) obtained from different donors and previously activated with phytohemagglutinin-L. PBL responded differently to treatment with RM-133, we observed a stimulation of cell proliferation and/or cytotoxicity in a dose-dependent manner. Based on these results, additional studies are currently underway to evaluate the selectivity of our lead compound against normal cell lines in a more detailed fashion.

B cells with immune-regulating function in transplantation

In transplantation, the contribution of B cells to the rejection or acceptance of the allograft is a topic of major interest. The presence of donor-specific antibodies in transplant recipients is often associated with decreased graft function and rejection, clearly indicating a pathogenetic role of B cells in transplantation. However, data from studies in humans and rodents suggest that under certain conditions, B cells have the capacity to control or regulate the immune response to a transplanted organ. Although a great deal of attention has been focused on B cells in human and murine models of autoimmunity, our understanding of the role of these cells in transplantation is limited at present. Indeed, results in this setting are controversial and seem to depend on the model system used or the clinical situation studied. Here, we review the current understanding of the various phenotypes and roles that have been associated with immune-regulating B cells. We also discuss the mechanisms employed by subsets of these regulatory B cells to control the immune response in transplant recipients and in animal models of transplantation.

Suppression of innate and adaptive B cell activation pathways by antibody coengagement of FcγRIIb and CD19

The Fc receptor (FcγRIIb) inhibits B cell responses when coengaged with B cell receptor (BCR), and has become a target for new autoimmune disease therapeutics. For example, BCR and FcγRIIb coengagement via the Fc-engineered anti-CD19 XmAb5871 suppresses humoral immune responses. We now assess effects of XmAb5871 on other activation pathways, including the pathogen-associated molecular pattern receptor, TLR9. Since TLR9 signaling is implicated in autoimmune diseases, we asked if XmAb5871 could inhibit TLR9 costimulation. We show that XmAb5871 decreases ERK and AKT activation, cell proliferation, cytokine, and IgG production induced by BCR and/or TLR9 signals. XmAb5871 also inhibited differentiation of citrullinated peptide-specific plasma cells from rheumatoid arthritis patients. XmAb5871 may therefore have potential to suppress pathogenic B cells in autoimmune diseases.

Analysis of host gene expression changes reveals distinct roles for the cytoplasmic domain of the Epstein-Barr virus receptor/CD21 in B-cell maturation, activation, and initiation of virus infection

Epstein-Barr virus (EBV) attachment to human CD21 on the B-cell surface initiates infection. Whether CD21 is a simple tether or conveys vital information to the cell interior for production of host factors that promote infection of primary B cells is controversial, as the cytoplasmic fragment of CD21 is short, though highly conserved. The ubiquity of CD21 on normal B cells, the diversity of this population, and the well-known resistance of primary B cells to gene transfer technologies have all impeded resolution of this question. To uncover the role(s) of the CD21 cytoplasmic domain during infection initiation, the full-length receptor (CD21=CR), a mutant lacking the entire cytoplasmic tail (CT), and a control vector (NEO) were stably expressed in two pre-B-cell lines that lack endogenous receptor. Genome-wide transcriptional analysis demonstrated that stable CD21 surface expression alone (either CR or CT) produced multiple independent changes in gene expression, though both dramatically decreased class I melanoma-associated antigen (MAGE) family RNAs and upregulated genes associated with B-cell differentiation (e.g., C2TA, HLA-II, IL21R, MIC2, CD48, and PTPRCAP/CD45-associated protein). Temporal analysis spanning 72 h revealed that not only CR- but also CT-expressing lines initiated latency. In spite of this, the number and spectrum of transcripts altered in CR- compared with CT-bearing lines at 1 h after infection further diverged. Differential modulation of immediate early cellular transcripts (e.g., c-Jun and multiple histones), both novel and previously linked to CD21-initiated signaling, as well as distinct results from pathway analyses support a separate role for the cytoplasmic domain in initiation of intracellular signals.

IMPORTANCE

Membrane proteins that mediate virus attachment tether virus particles to the cell surface, initiating infection. In addition, upon virus interaction such proteins may transmit signals to the interior of the cell that support subsequent steps in the infection process. Here we show that expression of the Epstein-Barr virus B-cell attachment receptor, CD21, in B cells that lack this receptor results in significant changes in gene expression, both before and rapidly following EBV-CD21 interaction. These changes translate into major signaling pathway alterations that are predicted to support stable infection.

Multiple regulatory mechanisms control B-1 B cell activation

B-1 cells constitute a unique subset of B cells identified in several species including mice and humans. B-1 cells are further subdivided into B-1a and B-1b subsets as the former but not the later express CD5. The B-1a subset contributes to innate type of immune responses while the B-1b B cell subset contributes to adaptive responses. B-1 cell responses to B cell receptor (BCR) as well as Toll-like receptor (TLR) ligation are tightly regulated due to the cross-reactivity of antigen specific receptors on B-1 cells to self-antigens. B-1 cells are elevated in several autoimmune diseases. CD5 plays a major role in down regulation of BCR responses in the B-1a cell subset. Reduced amplification of BCR induced signals via CD19 and autoregulation of BCR and TLR responses by B-1 cell produced IL-10 appear to have a role in regulation of both B-1a and B-1b B cell responses. Siglec G receptors and Lyn kinase also regulate B-1 cell responses but their differential role in the two B-1 cell subsets is unknown.

Can myofascial techniques modify immunological parameters?

OBJECTIVES

The objective was to determine the effect of myofascial techniques on the modulation of immunological variables.

DESIGN

Thirty-nine healthy male volunteers were randomly assigned to an experimental or control group.

INTERVENTIONS

The experimental group underwent three manual therapy modalities: suboccipital muscle release, so-called fourth intracranial ventricle compression, and deep cervical fascia release. The control group remained in a resting position for the same time period under the same environmental conditions.

OUTCOME MEASURES

Changes in counts of CD3, CD4, CD8, CD19, and natural killer (NK) cells (as immunological markers) between baseline and 20 minutes post-intervention.

RESULTS

Repeated-measures ANOVA revealed a significant time × groups interaction (F(1,35)=9.33; p=0.004) for CD19. There were no significant time × group interaction effects on CD3, CD4, CD8, or NK cell counts. Intrasubject analyses showed a higher CD19 count in the experimental group post-intervention versus baseline (t=-4.02; p=0.001), with no changes in the control group (t=0.526; p=0.608).

CONCLUSION

A major immunological modulation, with an increased B lymphocyte count, was observed at 20 minutes after the application of craniocervical myofascial induction techniques.

B-cell activity in children with malaria

Background

Recent studies implicate deficiency of red blood cell (RBC) complement regulatory proteins (CR1 and CD55) in the pathogenesis of malarial anaemia. This study explored the involvement of B cell CD21, which has an analogous role to RBC CR1.

Methods

In a case control study conducted in Kisumu District hospital, western Kenya, children with severe malaria anaemia (SMA) and those with uncomplicated malaria (UM) were assessed by flow cytometry for B cells (CD20+) numbers, expression levels of CD21 and deposition of C3dg and by ELISA for soluble CD21 (sCD21). Paired t tests were used to determine statistical significance at a = 0.05.

Results

Children with SMA had significantly higher lymphocyte count (9,627.7 ± 8786.1 SD vs. 5,507 ± 2436 SD, P = 0.04 in the UM group) and the computed geometric mean of mature B-cell numbers based on the absolute lymphocyte count was significantly higher for SMA group: 1,823 (1,126 to 2,982, 95% CI) and 826.6 (564 to 1,220, 95% CI)] for UM group (P = 0.003). SMA group also had a higher percentage of CD20+ B cells (26.8 ± 9.7SD vs 20.9 ± 9.01 SD in the UM) (P = 0.03), indicating considerable polyclonal B-cell activation. The CD21 median flourescence intensity was lower in the SMA (246.4 ± 87.4 SD vs 369 ± 137.7 SD) (P <0.0001), probably due to complement mediated shaving of CD21 by fixed tissue macrophages. The CD20+ B cells of SMAs had higher levels of the complement split product C3dg (18.35 ± 10 SD vs 11.5 ± 6.8 S.D), (P = 0.0002), confirming possible role of complement in CD21 removal. Unexpectedly, the SMAs had lower levels of sCD21 (226.5 ± 131.5 SD vs 341.4 ± 137.3 SD in the UM) (P < 0.0001), indicating that the shaved CD21 is not released to peripheral circulation.

Conclusions

These results implicate B-cell in pathophysiology of severe malaria that involves increased B-cell proliferation, increased complement deposition and subsequent loss of membrane-bound CD21. The loss of CD21 is not by the classical enzmatic cleavage.

Memory B cells and CD8⁺ lymphocytes do not control seasonal influenza A virus replication after homologous re-challenge of rhesus macaques

This study sought to define the role of memory lymphocytes in the protection from homologous influenza A virus re-challenge in rhesus macaques. Depleting monoclonal antibodies (mAb) were administered to the animals prior to their second experimental inoculation with a human seasonal influenza A virus strain. Treatment with either anti-CD8α or anti-CD20 mAbs prior to re-challenge had minimal effect on influenza A virus replication. Thus, in non-human primates with pre-existing anti-influenza A antibodies, memory B cells and CD8α⁺ T cells do not contribute to the control of virus replication after re-challenge with a homologous strain of influenza A virus.

Localization of BiP to translating ribosomes increases soluble accumulation of secreted eukaryotic proteins in an Escherichia coli cell-free system

The endoplasmic reticulum (ER) resident Hsp70 chaperone, BiP, docks to the Sec translocon and interacts co-translationally with polypeptides entering the ER to encourage proper folding. In order to recreate this interaction in Escherichia coli cell-free protein synthesis (CFPS) reactions, a fusion protein was formed between the ribosome-binding portion of the E. coli protein trigger factor (TF) and BiP. The biophysical affinity to ribosomes as well as the characteristic Hsp70 ATPase activity were both verified for the fusion protein. When added to E. coli-based CFPS reactions, the TF-BiP fusion chaperone increased soluble yields of several protein fragments that are normally secreted through the ER and have poor solubility in typical CFPS reactions. For comparison, a fusion between TF and the native E. coli Hsp70, DnaK, was also constructed. This fusion was also biologically active and increased soluble yields of certain protein targets in CFPS. The TF-BiP fusion described in this study can be seen as a first step in reconstituting and better understanding ER folding pathways in the prokaryotic environment of E. coli CFPS.

CR2+ marginal zone B cell production of pathogenic natural antibodies is C3 independent

Intestinal ischemia-reperfusion (IR)-induced damage requires complement receptor 2 (CR2) for generation of the appropriate natural Ab repertoire. Pathogenic Abs recognize neoantigens on the ischemic tissue, activate complement, and induce intestinal damage. Because C3 cleavage products act as ligands for CR2, we hypothesized that CR2(hi) marginal zone B cells (MZBs) require C3 for generation of the pathogenic Abs. To explore the ability of splenic CR2(+) B cells to generate the damaging Ab repertoire, we adoptively transferred either MZBs or follicular B cells (FOBs) from C57BL/6 or Cr2(-/-) mice into Rag-1(-/-) mice. Adoptive transfer of wild type CR2(hi) MZBs but not CR2(lo) FOBs induced significant damage, C3 deposition, and inflammation in response to IR. In contrast, similarly treated Rag-1(-/-) mice reconstituted with either Cr2(-/-) MZB/B1 B cells (B1Bs) or FOBs lacked significant intestinal damage and displayed limited complement activation. To determine whether C3 cleavage products are critical in CR2-dependent Ab production, we evaluated the ability of the natural Ab repertoire of C3(-/-) mice to induce damage in response to IR. Infusion of C3(-/-) serum into Cr2(-/-) mice restored IR-induced tissue damage. Furthermore, Rag-1(-/-) mice sustained significant damage after infusion of Abs from C3(-/-) but not Cr2(-/-) mice. Finally, adoptive transfer of MZBs from C3(-/-) mice into Rag-1(-/-) mice resulted in significant tissue damage and inflammation. These data indicate that CR2 expression on MZBs is sufficient to induce the appropriate Abs required for IR-induced tissue damage and that C3 is not critical for generation of the pathogenic Abs.

Molecular underpinning of B-cell anergy

A byproduct of the largely stochastic generation of a diverse B-cell specificity repertoire is production of cells that recognize autoantigens. Indeed, recent studies indicate that more than half of the primary repertoire consists of autoreactive B cells that must be silenced to prevent autoimmunity. While this silencing can occur by multiple mechanisms, it appears that most autoreactive B cells are silenced by anergy, wherein they populate peripheral lymphoid organs and continue to express unoccupied antigen receptors yet are unresponsive to antigen stimulation. Here we review molecular mechanisms that appear operative in maintaining the antigen unresponsiveness of anergic B cells. In addition, we present new data indicating that the failure of anergic B cells to mobilize calcium in response to antigen stimulation is not mediated by inactivation of stromal interacting molecule 1, a critical intermediary in intracellular store depletion-induced calcium influx.

The small interferon-induced transmembrane genes and proteins

Interferon-induced transmembrane (IFITM) genes are transcribed in most tissues and are with the exception of IFITM5 interferon inducible. They are involved in early development, cell adhesion, and control of cell growth. Most IFITM genes are activated in response to bacterial and viral infections, and the exact host immune defense mechanisms are still unknown. Elevated gene expression triggered by past or chronic inflammation could prevent spreading of pathogens by limiting host cell proliferation. Accordingly, induction in cells with low basal protein levels is sufficient to drive growth arrest and a senescence-like morphology. On the other hand, loss of IFITM levels in cancer is correlated with pronounced malignancy; thus, these genes are considered as tumor suppressors. However, several cancer cells have deregulated high levels of IFITM transcripts, indicating a tumor progression stage where at least one of the interferon-controlled antiproliferative pathways has been silenced. Phylogenetic analyses of the protein coding genomic sequences suggest a single interferon-inducible gene in the common ancestor of rodents and primates. Biological functions studied so far may have evolved in parallel, and functional characterization of IFITM proteins will provide insight into innate immune defense, cancer development, and other pathways.

The conundrum of inhibitory signaling by ITAM-containing immunoreceptors: potential molecular mechanisms

Immunoreceptor signals must be appropriately transduced and regulated to achieve effective immunity while controlling inflammation and autoimmunity. It is generally held that these processes are mediated by the interplay of distinct activating and inhibitory receptors via conserved activating (ITAM) and inhibitory (ITIM) signaling motifs. However, recent evidence indicates that under certain conditions incomplete phosphorylation of ITAM tyrosines leads to inhibitory signaling. This new regulatory function of ITAMs has been termed ITAMi (inhibitory ITAM). Here we discuss the potential molecular mechanisms of inhibitory signaling by ITAM-containing receptors.

The long winding road toward understanding the molecular mechanisms for B-cell suppression by 2,3,7,8-tetrachlorodibenzo-p-dioxin

Suppression of humoral immune responses by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was first reported in the mid-1970s. Since this initial observation, much effort has been devoted by many laboratories toward elucidation of the cellular and molecular mechanisms responsible for the profound impairment of humoral immune responses by TCDD, which is characterized by decreased B cell to plasma cell differentiation and suppression of immunoglobulin production. These efforts have led to a significant body of research demonstrating a direct effect of TCDD on B-cell maturation and function as well as a requisite but as yet undefined role of the aryl hydrocarbon receptor (AhR) in these effects. Likewise, a number of molecular targets putatively involved in mediating B-cell dysfunction by TCDD, and other AhR ligands, have been identified. However, our current understanding has primarily relied on findings from mouse models, and the translation of this knowledge to effects on human B cells and humoral immunity in humans is less clear. Therefore, a current challenge is to determine how TCDD and the AhR affect human B cells. Efforts have been made in this direction but continued progress in developing adequate human models is needed. An in-depth discussion of these advances and limitations in elucidating the cellular and molecular mechanisms putatively involved in the suppression of B-cell function by TCDD as well as the implications on human diseases associated in epidemiological studies with exposure to TCDD and dioxin-like compounds is the primary focus of this review.