Ia antigens on antigen-presenting cells do not carry the same Ia specificities as detected on suppressor and helper T cells.
The passage of spleen cells through a tightly packed nylon wool column partially separated two populations of cells required for the antigen-induced secondary proliferative response of T cells. The proliferating T cells were in the nylon wool column-passed cell population, but the addition of a small number of nylon-wool-adherent cells was required for their maximal proliferative response. Such adherent cells were non-T, non-B, Ia antigen-positive cells serving as antigen-presenting cells. Ia determinants on this cell type are encoded in two separate I subregions, I-A and I-E/C, and they are expressed simultaneously on the same cells. Antisera specific for I-J subregion gene products having as a known activity the killing of antigen-specific suppressor and helper T cells were unable to kill antigen-presenting adherent cells. The results indicated that at least I-J subregion gene products expressed on suppressor and helper T cells are not present on antigen-presenting accessory cells. The Ia specificities detected on accessory cells follow the cross-reactive pattern found in Ia molecules of B cells, and thus antigen-presenting cells carry Ia antigen identical to those of B cells, and not those of T cells.
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D000939:Epitopes; D000949:Histocompatibility Antigens Class II