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B-cell Tolerance (b-cell + tolerance)
Selected AbstractsConstitutive activation of Bruton's tyrosine kinase induces the formation of autoreactive IgM plasma cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2010Rogier Kersseboom Abstract B-cell receptor (BCR)-mediated signals provide the basis for B-cell differentiation in the BM and subsequently into follicular, marginal zone, or B-1 B-cell subsets. We have previously shown that B-cell-specific expression of the constitutive active E41K mutant of the BCR-associated molecule Bruton's tyrosine kinase (Btk) leads to an almost complete deletion of immature B cells in the BM. Here, we report that low-level expression of the E41K or E41K-Y223F Btk mutants was associated with reduced follicular B-cell numbers and significantly increased proportions of B-1 cells in the spleen. Crosses with 3-83,, and VH81X BCR Tg mice showed that constitutive active Btk expression did not change follicular, marginal zone, or B-1 B-cell fate choice, but resulted in selective expansion or survival of B-1 cells. Residual B cells were hyperresponsive and manifested sustained Ca2+ mobilization. They were spontaneously driven into germinal center-independent plasma cell differentiation, as evidenced by increased numbers of IgM+ plasma cells in spleen and BM and significantly elevated serum IgM. Because anti-nucleosome autoantibodies and glomerular IgM deposition were present, we conclude that constitutive Btk activation causes defective B-cell tolerance, emphasizing that Btk signals are essential for appropriate regulation of B-cell activation. [source] The immunological basis of B-cell therapy in systemic lupus erythematosusINTERNATIONAL JOURNAL OF RHEUMATIC DISEASES, Issue 1 2010Mo Yin MOK Abstract Loss of B-cell tolerance is a hallmark feature of the pathogenesis in systemic lupus erythematosus (SLE), an autoimmune disease that is characterized by hypergammaglobulinemia and autoantibody production. These autoantibodies lead to formation of immune-complex deposition in internal organs causing inflammation and damage. Autoreactive B-cells are believed to be central in the pathophysiology of SLE. Other than its role in the production of antibodies that mediate humoral immune response, B-cells also function as antigen-presenting cells and are capable of activating T-cells. Activated B-cells may also produce pro-inflammatory cytokines that aggravate local inflammation. Abnormal B-cell homeostasis has been described in SLE patients. This may occur as a result of intrinsic B-cell defect or from aberrant regulation by maturation and survival signals. B-cell-based therapy is the current mainstream of research and development of novel therapies in SLE patients with severe and refractory disease. Potential cellular and molecular targets for B-cell therapies include cell surface molecules such as CD20 (rituximab) and CD22 (epratuzumab); co-stimulatory molecules involved in B-cell,T-cell interaction such as CTLA4 and B7 molecules (abatacept); maturation and growth factors such as B-cell activating factor and a proliferation-inducing ligand (belimumab, briobacept, atacicept) and B-cell tolerogen (abetimus). This article provides an overview on normal B-cell physiology and abnormal B-cell biology in SLE that form the immunological basis of B-cell-targeted therapy in the treatment of these patients with refractory diseases. [source] Absence of Donor-Specific Anti-HLA Antibodies After ABO-Incompatible Heart Transplantation in Infancy: Altered Immunity or Age?AMERICAN JOURNAL OF TRANSPLANTATION, Issue 1 2010S. Urschel Specific B-cell tolerance toward donor blood group antigens develops in infants after ABO-incompatible heart transplantation, whereas their immune response toward protein antigens such as HLA has not been investigated. We assessed de novo HLA-antibodies in 122 patients after pediatric thoracic transplantation (28 ABO-incompatible) and 36 controls. Median age at transplantation was 1.7 years (1 day to 17.8 year) and samples were collected at median 3.48 years after transplantation. Antibodies were detected against HLA-class I in 21 patients (17.2%), class II in 18 (14.8%) and against both classes in 10 (8.2%). Using single-antigen beads, donor-specific antibodies (DSAs) were identified in six patients (all class II, one additional class I). Patients with DSAs were significantly older at time of transplantation. In patients who had undergone pretransplant cardiac surgeries, class II antibodies were more frequent, although use of homografts or mechanical heart support had no influence. DSAs were absent in ABO-incompatible recipients and class II antibodies were significantly less frequent than in children with ABO-compatible transplants. This difference was present also when comparing only children transplanted below 2 years of age. Therefore, tolerance toward the donor blood group appears to be associated with an altered response to HLA beyond age-related effects. [source] American Society of Transplantation Symposium on B Cells in Transplantation: Harnessing Humoral Immunity from Rodent Models to Clinical PracticeAMERICAN JOURNAL OF TRANSPLANTATION, Issue 6 2007A. D. Kirk There is growing awareness that B cells and alloantibodies are important mediators of both acute and chronic allograft injury. Unfortunately, few therapies are clinically available to mitigate the function of B cells or the effects of established alloantibody. As a result, many sensitized people await transplantation without a suitable donor, and several rejection syndromes are emerging that appear to involve B cells either as antibody producers or as antigen-presenting cells. In recognition of this unmet need in transplantation, the American Society of Transplantation organized a Symposium on B cells in Organ Transplantation to foster interest in this topic amongst basic researchers attending the annual meeting of the American Association of Immunologists. This manuscript will give an overview of the presentations from this symposium including the current risks of allosensitization, adaptive accommodation, approaches toward B-cell tolerance for allo- and xenoantigens and clinical application of these concepts in ABO incompatible neonatal cardiac transplantation. [source] |