Serum-mediated suppression of nonspecific B cell activation. I. Description of an inhibitory capacity in normal mouse serum and characterization of the inhibitory component.
Normal mouse serum (NMS) in relatively small amounts was demonstrated to inhibit in vitro splenic B cell activation by several B cell mitogens, polyclonal activators, and T-independent antigens. Proliferative and polyclonal responses elicited by bacterial endotoxin (ET), PPD, or Fc fragment of Ig were suppressed routinely 90% or greater when 0.5% homologous NMS was present in the culture medium. Similar suppression of T-independent antibody responses to TNP-ET and TNP-Ficoll was also observed. In contrast, activation by the T cell mitogen, Con A, and a T-dependent antigen response to SRBC was not inhibited by NMS. Suppression of B cell responses by NMS was not dependent on T cells. Preliminary characterization of NMS-In revealed a m.w. of approximately 200,000, an isoelectric point of 5, and solubility in 40% saturated ammonium sulfate. Both functionally and physically, NMS-In appears to be different from other currently relatively well characterized regulatory substances in serum. NMS-In was found in plasma as well as in serum, suggesting that NMS-In may function naturally in vivo to minimize nonspecific activation of B cells.
D000818:Animals; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology*; D001769:Blood / Q000378:metabolism*; D002999:Clone Cells / Q000276:immunology; D004731:Endotoxins / Q000494:pharmacology; D000939:Epitopes; D005260:Female; D007141:Immunoglobulin Fc Fragments; D007526:Isoelectric Point; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008805:Mice, Inbred A; D008809:Mice, Inbred C3H; D008808:Mice, Inbred CBA; D008934:Mitogens / Q000494:pharmacology; D008970:Molecular Weight; D013601:T-Lymphocytes / Q000276:immunology; D014373:Tuberculin / Q000276:immunology
D004731:Endotoxins; D000939:Epitopes; D007141:Immunoglobulin Fc Fragments; D008934:Mitogens; D014373:Tuberculin