title: Activation of secondary cytotoxic lymphocytes by cell-free factors from I-region-primed and D-region-primed lymphocytes.
abstract: Cell co-operation in the generation of secondary cytotoxic responses was studied by selectively sensitizing lymphocytes in mixed lymphocyte culture (MLC) across I or D region difference and by combining the primed lymphocytes in the secondary MLC. Secondary cytotoxic responses were induced in D-region-primed lymphocytes by restimulation with the original priming D-region antigens, by co-culturing with the I-region-primed lymphocytes in the presence of the priming I-region antigens, or by cell-free supernatants obtained 24 h after the restimulation of D-region-primed lymphocytes and I-region-primed lymphocytes, The active MLC supernatants produced by both I-region-primed and D-region-primed cells also induced accelerated proliferative responses in D-region-primed lymphocytes. Heat-treatment or ultraviolet irradiation of the stimulator cells eliminated the capacity of the cells to induce the production of CTL-helper factor in I-region-primed and D-region-primed lymphocytes. It was concluded that both I-region-primed and D-region-primed lymphocytes produce a cell-free factor which induces proliferation and secondary cytotoxicity in D-region-primed lymphocytes. The possible participation of D-region reactive helper T cells and D-region reactive cytotoxic T cells in the cytotoxic responses to D-region antigens in the absence of I-region difference is discussed.
mesh_terms: D000818:Animals; D002474:Cell-Free System; D003602:Cytotoxicity, Immunologic; D004247:DNA / Q000096:biosynthesis; D000939:Epitopes; D006183:H-2 Antigens / Q000276:immunology*; D006358:Hot Temperature; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000528:radiation effects; D051379:Mice; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology; D014466:Ultraviolet Rays
chemical_list: D000939:Epitopes; D006183:H-2 Antigens; D004247:DNA