Aversa, S

Aversa, S. of preactivated B cells. In addition, sSLAM enhances production of IgM, IgG, and IgA by B cells activated BRD9185 by antiCD40 mAbs. SLAM has recently been shown to be a high affinity self-ligand, and the present data suggest that signaling through homophilic SLAMCSLAM binding during BCB and BCT cell interactions enhances the growth and differentiation of activated B cells. Bcell activation is initiated after acknowledgement of specific antigen by cell surface Ig, BRD9185 which in naive, unprimed B cells is usually of IgM or IgD isotype. Cytokines and membranebound costimulatory molecules expressed by activated CD4+ T cells are required for subsequent proliferation, Ig isotype switching and differentiation of activated B cells. Cytokines produced by Th2-type cells, such as IL-4, IL-5, IL-13, are considered to be primarily involved in providing help for B cells, whereas Th1-type cytokines, IL-2 and IFN-, mediate delayed-type hypersensitivity reactions and activate macrophages (1C3). In addition to T Rabbit Polyclonal to GLUT3 cells, monocytes can regulate B cell proliferation and differentiation through release of cytokines, such as IL-6, IL-8, and IL-10 (4C6), and B cell proliferation and differentiation also appear to be regulated by autocrine mechanisms. IL-1, IL-6, IL-10, TNF-, and lymphotoxin have been shown to be produced, among other cell types, by activated B cells and they enhance proliferation and differentiation of these cells (7C11). The CD40 ligand (CD40L)1 on activated CD4+ T cells, which interacts with CD40 on B cells (12), was shown to be a potent membrane-bound costimulatory molecule for proliferation and differentiation of both human and murine B cells (13C17). The B cell antigen CD19, the ligand of which remains to be characterized, has also been shown to mediate maturation, proliferation and differentiation of B cells (18). In addition, CD70, a member of the TNF family expressed by activated B and T cells, and the BRD9185 membrane form of TNF-, expressed by activated and HIV-infected T cells, are involved in productive TCB cell interactions (19C21). Although several surface molecules can mediate TCB cell collaboration, the role of CD40L appears to be crucial, as is clearly exhibited in patients with hyperIgM syndrome, who are unable to produce IgG, IgA, or IgE because of mutations in their genes encoding CD40L (22C25). However, the patients have normal or elevated levels of IgM and normal numbers of B cells in the blood circulation indicating that a CD40L-impartial pathway of B cell proliferation and differentiation is usually operational in these patients. Moreover, CD40L-deficient mice have normal Ab responses against thymus-independent antigens (26, 27), and some T cell clones from patients with mutated CD40L genes induce Ig isotype switching even in the presence of neutralizing antiCTNF- mAbs (28), supporting the conclusion that yet to be characterized costimulatory molecules contribute to the growth, Ig isotype switching and differentiation of activated B cells. Signaling lymphocytic activation molecule (SLAM) is usually a 70-kD glycoprotein expressed by CD45RO+ T cells, immature thymocytes, and a proportion of B cells (29). SLAM is usually BRD9185 a member of the immunoglobulin gene superfamily and belongs to the CD2 family of cell surface molecules (29, 30). SLAM has limited homology to CD48 (26%), CD58/LFA-3 (17%), and 2B4 (28%), a signaling molecule expressed on murine NK and cytotoxic T cells (31). Activated human T cells express, in addition to membrane-form of SLAM (mSLAM), mRNA encoding a soluble, secreted form of SLAM (sSLAM) lacking 30 amino acids (aa) encompassing the entire 22-aa transmembrane region (29). In addition, a cytoplasmic (c) form lacking the leader sequence and a variant membrane (vm)SLAM with a truncated cytoplasmic tail were identified (29). SLAM was recently shown to be a high-affinity self-ligand with an affinity constant of 0.1 nM (Cocks, B.G., G. Aversa, S. Balasubramanian, C.-C.J. Chang, B. Bennett, D. Peterson, J.M. Carballido, J. Punnonen, and J.E. de Vries, manuscript submitted for publication). SLAM-Ig fusion protein specifically bound to SLAM transfectants and to surface-immobilized SLAM as shown.