title: Role of a nonimmunoglobulin cell surface determinant in the activation of B lymphocytes by thymus-independent antigens.
abstract: Lyb 5 is a B-cell alloantigen which is expressed on 50-60% of B cells. It was defined originally on the basis of cytotoxicity. We have described a new reactivity within the anti-Lyb 5 serum on the basis of selective inhibition of antibody responses in vitro by this antiserum in the absence of complement. This inhibitory activity of anti-Lyb 5.1 serum appears to be due to recognition of antigenic determinants different from the prototype antigens detected in the cytotoxicity assay. Anti-Lyb 5 serum incorporated into spleen cell cultures selectively inhibits antibody responses to a class of thymus-independent antigens (TI-2) previously characterized by their failure to elicit antibody formation in immature mice or in the defective CBA/N strain. Responses to optimal concentrations of TI-1 antigens, which can induce antibody synthesis in these mice, are unaffected by the addition of anti-Lyb 5.1 serum. The B-cell alloantigen defined by this functional assay is designated tentatively Lyb 7 and it is shown to be distinct from cell surface immunoglobulins. Lyb 7 appears to have a role in the activation of B lymphocytes by the TI-2 class of thymus-independent antigens.
mesh_terms: D000917:Antibody Formation; D000937:Antigen-Antibody Reactions; D000954:Antigens, Surface / Q000032:analysis*; D001402:B-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D003911:Dextrans / Q000276:immunology; D000939:Epitopes; D005362:Ficoll / Q000276:immunology; D007518:Isoantibodies; D007519:Isoantigens / Q000032:analysis*; D008213:Lymphocyte Activation; D014301:Trinitrobenzenes / Q000276:immunology
chemical_list: D000954:Antigens, Surface; D003911:Dextrans; D000939:Epitopes; D007518:Isoantibodies; D007519:Isoantigens; D014301:Trinitrobenzenes; D005362:Ficoll