title: T cell activation of antigen-specific antibody responses by large B cells is MHC restricted.
abstract: The activation of small, resting B cells for antibody synthesis by helper T cells has been proposed to require an MHC-restricted interaction between the T and B cells. Large, activated B lymphocytes were, in contrast, thought to be activated by an unrestricted pathway. We re-examined this issue and found that both large and small size fractionated murine B lymphocytes required an MHC-restricted interaction with helper T cells to be activated for specific antibody synthesis. Polyspecific antibody synthesis in the same cultures was not dependent upon an MHC-restricted T-B interaction for any size category of B cell. These results are interpreted as reflecting the ability of antigen-specific B cells to focus and present antigen to T cells, in contrast to B cells of random specificity, which have no effective focusing mechanism for a given experimental antigen. We found that the polyspecific response required much higher antigen concentrations than the antigen-specific response, a result consistent with the antigen-focusing hypothesis.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D000941:Antigens; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002453:Cell Cycle; D004306:Dose-Response Relationship, Immunologic; D008211:Lymphocyte Cooperation; D008285:Major Histocompatibility Complex; D051379:Mice; D008807:Mice, Inbred BALB C; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D000941:Antigens