title: A human T-independent B lymphocyte mitogen extracted from Nocardia opaca.
abstract: Nocardia water soluble mitogen (NWSM), a mitogen specific for mouse and rabbit B cells, activates blood, spleen, and tonsil lymphocytes from all the humans tested. Evidence is presented that it acts selectively on human B lymphocytes. B-enriched cells were recovered from anti-Ig-coated Sephadex columns or after elimination of E rosette-forming cells: they were able to incorporate tritiated thymidine when they were cultivated in the presence of NWSM whereas they were not activated by PWM. Conversely T-enriched suspensions did not respond to NWSM although they were able to be stimulated by PHA and PWM. Moreover, the response to NWSM remained unchanged after T cells had been killed by anti-HTLA serum and complement and disappeared after B cells had been killed by anti-HBLMA serum. After stimulation by NWSM, the number of direct plaque-forming cells to HRBC, LPS, and TNP was significantly increased, showing a polyclonal activation of human B lymphocytes. Since no evidence of T cell help for B cell activation has been found, NWSM thus appears to be a T-independent human B lymphocyte mitogen.
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology*; D002469:Cell Separation; D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007700:Kinetics; D008213:Lymphocyte Activation; D008934:Mitogens; D009615:Nocardia / Q000276:immunology*; D014066:Palatine Tonsil / Q000276:immunology; D013045:Species Specificity; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D008934:Mitogens