title: Serum-mediated suppression of nonspecific B cell activation. I. Description of an inhibitory capacity in normal mouse serum and characterization of the inhibitory component.
abstract: 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.
mesh_terms: 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
chemical_list: D004731:Endotoxins; D000939:Epitopes; D007141:Immunoglobulin Fc Fragments; D008934:Mitogens; D014373:Tuberculin