| CD154(CD40L, gp39, TRAP) is a 33-kDa glycoprotein mainly expressed as a type II intergral membrane protein on the surface of activated CD4+T cells and platelets. CD 154, encoded by a gene located at Xq26.3-Xq27.1, belongs to the tumor necrosis factor(TNF) superfamily. In contrast, its receptor, CD40, is expressed during all stages of B cell development and differentiation, antigen-presenting cells(APCs) as well as many carcinoma cells, and belongs to the tumor necrosis factor receptor(TNFR) superfamily.The demonstration of the critical role of CD40-CD154 interaction in vivo came from the discovery that the hyper IgM syndrome(HIGM), an X-linked immunodeficiency, was due to a genetic alteration of the CD 154 gene. HIGM is characterized by a severe impairment of T cell dependent antibody responses with no B cell memory, deficient induction of immunoglobulin somatic mutation and little or no circulating IgG, IgA or IgE antibodies.CD40-CD154 interaction has been reported to be pivotal for the induction of both the humoral and cellular immune response. In vivo studies using a blocking anti-CD 154 mAb, CD40-deficient or CD154-deficient mice demonstrated a role for the CD40-CD154 pathway in the generation of both the primary and secondary response to thymus-dependent antigens, in isotype switching and in the formation of germinal centers. The contribution of the CD40-CD154 interaction to the process of T cell priming, differentiation, and effector functions has been extensively investigated. Activation of CD40 has important effects on the expression of costimulatory molecules such as CD80, CD86, CD54/ICAM-1 and CD58/LFA-3 and the production of IL-12, and hence Thl(as opposed to Th2) responses. Priming of CD8+ cytotoxic Tlymphocytes(CTL) generally requires the participation of CD4+Th cells and APCs. Recent theory is that, rather than being directly supplied to the CTL by the Th cells, Th cells are delivered through activation of APCs called "conditioning APCs", which can prime the CTL directly.The availability of either blocking anti-mouse CD 154 antibodies or both CD40 and CD 154 knockout mice has offered the possibility to test the role of CD40-CD154 interactions in several disease models. Administration of blocking anti-CD 154 has been demonstrated to be beneficial in several models of autoimmunity, including spontaneous diseases like lupus nephritis in SNFl mice or diabetes in NOD mice or in experimentally induced forms of disease like experimental autoimmune encephalomyelitis(EAE). CD40-CD154 interactions play a critical role in T cell priming and have been suggested to prohibit tolerance induction. Therefore, interference with CD40 activation has been extensively investigated to prolong the survival of experimentally transplanted organs. Treatment with anti-CD 154 prolonged survival of transplanted organs in some murine models including allografts of heart, skin, aorta and pancreatic islets. Significantly, beneficial effects of anti-CD 154 treatment have also been observed in a rhesus monkey model of kidney transplantation.In our study, using human CD 154 gene transfected murine fibroblast cell line (CD154-T), which expressed CD 154 strongly, to immunize Balb/c mice, we generated two murine mAbs against human CD154(clones 1B1, 4F1). The biological functions of 1B1 and 4F1 were investigated in mixed lymphocyte reaction(MLR) and co-cultures consisted of CD4+T cells and vascular endothelial cells. Moreover, we found that 1B1 and 4F1 could be used to develop an ELISA optimized to analyze soluble CD 154 concentrations. This ELISA was used to analyze sCD154 concentrations in serum and plasma of healthy adults, aplastic anemia(AA), idiopathic thrombocytopenic purpura(ITP) and rheumatoid arthritis(RA) patients.PART ONEThe biological effects of two novel monoclonal antibodies against CD154 in alloreaction1. The induction of CD4+T cell alloantigen hyporesponsiveness by ex vivo anti-CD154 monoclonal antibodiesTo purify CD4+T cells as responder cells, healthy adult peripheral blood mononuclear cells(PBMCs)... |
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