title: Helper T cell-replacing factors secreted by thymus-derived cells and macrophages: cellular requirements for B cell activation and synergistic properties.
abstract: The biologic activities of helper T cell-replacing factors derived from concanavalin A-stimulated murine T cells (TRF-T) and from lipopolysaccharide-activated macrophages (TFR-M) have been compared. TRF-T stimulates immune responses to heterologous erythrocyte antigens (SRBC and BRBC) in T cell-depleted spleen cultures but not in macrophage-depleted spleen cultures. TRF-M stimulates immune responses in both T cell-depleted and macrophage-depleted spleen cultures. Under conditions where LPS stimulates the release of TRF-M from cultures of activated macrophages, TRF-t has no effect on TFR-M production. Thus. TRF-T does not appear to function by stimulating the release of TRF-M from macrophages. In macrophage-depleted spleen cultures, saturating concentrations of TRF-T and TRF-M when mixed together exhibit striking synergistic effects on the induction of immune responses to erythrocyte antigens. The kinetics of the synergistic effects of TRF-M and TRF-T are consistent with an effect of TRF-M on the production of TRF-T sensitive B cells.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology*; D007111:Immunity, Cellular; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D010527:Perissodactyla; D012756:Sheep; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism