title: Identification of Ia on a subpopulation of human T lymphocytes that stimulate in a mixed lymphocyte reaction.
abstract: The delineation of discrete subpopulations of human T lymphocytes has permitted preliminary analyses of the complex cellular network regulating the immune response in man. We previously showed that a subset of T lymphocytes, designated as theophylline-sensitive because of their inability to bind sheep red blood cells in the presence of the drug, are responsible for antigen-specific suppression or regulation in an in vitro plaque-forming cell assay. We now show that 25 to 45% of these theophylline-sensitive T cells were Ia-positive by immunofluorescence with a rabbit antiserum raised against purified B lymphoblast surface antigenic material. These data suggested that 4 to 7% of peripheral blood T cells carry Ia determinants. The presence of Ia determinants on this T cell subset was confirmed by gel analysis of radioiodinated surface material. Furthermore, in mixed lymphocyte culture, the theophylline-sensitive cells demonstrated HLA-D determinants and were 10-fold more potent stimulators than equal numbers of B lymphocytes. The presence of Ia determinants on these T cells indicates the expression of major histocompatibility complex-related regulatory gene products on a specific human T lymphocyte subpopulation.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D002469:Cell Separation; D011232:Chemical Precipitation; D000939:Epitopes; D006649:Histocompatibility Antigens; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D007784:Lactoperoxidase / Q000494:pharmacology; D007959:Lymphocyte Culture Test, Mixed; D012397:Rosette Formation; D012756:Sheep; D013601:T-Lymphocytes / Q000145:classification*; D013806:Theophylline / Q000494:pharmacology
chemical_list: D000939:Epitopes; D006649:Histocompatibility Antigens; D007106:Immune Sera; D013806:Theophylline; D007784:Lactoperoxidase