title: Interactions of small B lymphocytes with unprimed noncytolytic T cells: dissociation between "presentation" and growth induction.
abstract: The accessory cell requirements in lectin-dependent triggering and growth of unprimed Lyt-2-T lymphocytes were analyzed by quantitatively comparing the ability of small B cells and peritoneal macrophages to either induce reactivity to growth factors or support growth. Lightly or nonirradiated small B cells were 15 to 30-fold less efficient as compared to T cell-depleted peritoneal cell populations, in the support of the lectin-stimulated Lyt-2-T cell proliferation. In contrast, lightly irradiated small B lymphocytes were quantitatively as efficient as macrophages in mediating lectin-driven Lyt-2-T cell proliferation, if relevant supernatants were added into culture. Finally, supernatants derived from cultures where T-small B cell ratios were optimal for growth of responder Lyt-2-lymphocytes were two orders of magnitude less efficient than conditioned medium obtained from cultures containing optimal T-macrophage ratios, in their ability to support growth of activated T cells. We conclude from these experiments that: in contrast to cytolytic T cell precursors, lectin-dependent induction of unprimed Lyt-2- T lymphocytes requires accessory cells; small B cells and macrophages are equally competent in this respect; and growth support by small B cell populations is due to contamination by macrophages which are the only cell type performing this function. We therefore interpret reports on Lyt-2- T cell proliferation upon stimulation with high numbers of small B cells as a two-step process: "presentation" and induction of T cells which is essentially B cell dependent, and factor production ensured by contaminating macrophages.
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000145:classification / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology* / Q000502:physiology / Q000528:radiation effects; D002470:Cell Survival; D004307:Dose-Response Relationship, Radiation; D007958:Leukocyte Count; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000528:radiation effects; D008211:Lymphocyte Cooperation; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010641:Phenotype; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*
chemical_list: D008070:Lipopolysaccharides