title: Epitope-specific antibody feedback regulation of the humoral immune response against sheep erythrocytes in vitro: specific effects of anti-antigen antibody vs nonspecific T cell activities.
abstract: Antibody formed during a 1st in vitro anti-SRBC PFC response had previously been shown to inhibit the formation of PFC when added to a 2nd, freshly established test culture. This effect was to a large extent restricted to test cultures containing B cells sharing VH genes with the B cells producing the initial antibody, and this suggested that anti-SRBC antibody acted via triggering of an anti-idiotypic antibody of TS response. In the present studies this system has been further characterized. First, such antibody feedback occurred in cultures of purified and anti-Lyt2 antiserum and complement-treated surface Ig-positive cells in which TH were substituted for by T-replacing factor. Thus, T cells were not required. Moreover, T cells were always nonspecifically activated in cultures containing FCS. Secondly, anti-idiotypic antibody-like activity was not detected in the sense that generation of inhibitory antibody was never found to be dissociated from generation of anti-SRBC antibody, and LPS-dependent anti-SRBC PFC responses were not inhibited. However, feedback inhibition of SRBC-dependent responses was reversed at increased SRBC concentrations. Thirdly, the feedback mechanism was highly epitope specific, whereas in vitro anti-SRBC PFC responses of different mouse strains (B6 vs BALB/c) were directed to a large extent against different epitopes. These data strongly suggest that VH-restricted inhibitory activity of antibody in this system is a manifestation of epitope specificity of the antibody feedback and not of idiotype specificity, i.e., that anti-SRBC antibody acts via masking of epitopes.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000939:Epitopes; D004912:Erythrocytes / Q000276:immunology; D005246:Feedback; D005260:Female; D006462:Hemolytic Plaque Technique; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D012756:Sheep; D013601:T-Lymphocytes / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology
chemical_list: D000939:Epitopes; D008070:Lipopolysaccharides