title: Direct activation of CD8+ cytotoxic T lymphocytes by dendritic cells.
abstract: Recent experiments (11-13) have shown that antigen-specific, CD8+, CD4- T lymphocytes can be induced to proliferate and become killer cells in the absence of a second population of "helper" CD8-, CD4+ cells. We have studied early events in the activation of CD4+ and CD8+ T cell subsets in the primary mixed leukocyte reaction. Dendritic cells are a major if not essential accessory cell for the activation of both subpopulations. Antigen-bearing macrophages fail to stimulate unprimed CD8+ cells, but act as targets for the sensitized cytolytic lymphocytes that are induced by dendritic cells. The initial proliferative response is comparable for CD4+ and CD8+ lymphocyte subsets. For both subpopulations, dendritic cells efficiently cluster the responding lymphocytes on the first day and induce the release of IL-2. The data indicate that CD4+ and CD8+ lymphocytes can be activated by a similar mechanism, and illustrate the special role of dendritic cells in the sensitization stage of cell-mediated immunity.
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology*; D002449:Cell Aggregation; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology*; D005260:Female; D007962:Leukocytes / Q000276:immunology; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface