title: Selective suppression of an early step in human B cell activation by cyclosporin A.
abstract: The effect of cyclosporin A (CsA), a fungal metabolite with immunosuppressive properties, on the induction of human B cell proliferation and differentiation, has been described. CsA had a selective inhibitory effect on the activation phase of the cell cycle vs. the proliferation phase following preactivation of the cells. Cell enlargement and RNA synthesis of small resting B cells triggered by anti-mu were inhibited by addition of CsA (5-500 ng/ml). The inhibitory effect of CsA was found only when the drug was added within 24 h of initiation of culture. In marked contrast, once small B cells were activated by anti-mu, the resulting large, activated B cells could be induced to initiate DNA synthesis by incubation with B cell growth factor (BCGF), and addition of CsA (1-1,000 ng/ml) to the culture did not suppress this BCGF-induced B cell proliferation. Addition of CsA to cultures of B cells which had been preactivated with Staphylococcus aureus Cowan strain I (SAC) and were already proliferating did not suppress B cell differentiation factor (BCDF)-induced differentiation of these cells. Thus, these data indicate that CsA can be used as a pharmacologic tool to dissect out human B cell responses into two distinct steps: (a) the initial activation step induced by anti-Ig, which is characterized by cell enlargement, RNA synthesis, and expression of receptors for BCGF; and (b) the proliferative step induced by BCGF in these preactivated B cells that undergo DNA synthesis and can then go on to differentiate in the presence of BCDF. In this regard, CsA selectively suppresses an early step of human B cell activation and has little inhibitory effect on the subsequent factor-dependent proliferation and differentiation.
mesh_terms: D000293:Adolescent; D000328:Adult; D000888:Antibodies, Anti-Idiotypic / Q000502:physiology; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation / Q000187:drug effects; D002648:Child; D003524:Cyclosporins / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D006133:Growth Substances / Q000502:physiology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D015847:Interleukin-4; D008213:Lymphocyte Activation / Q000187:drug effects*; D012313:RNA / Q000096:biosynthesis; D013211:Staphylococcus aureus / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D003524:Cyclosporins; D006133:Growth Substances; D007166:Immunosuppressive Agents; D015847:Interleukin-4; D012313:RNA; D004247:DNA