title: Ia determinants on human T-cell subsets defined by monoclonal antibody. Activation stimuli required for expression.
abstract: The nature of Ia antigens which appear on human T cells after activation and the stimuli required for their expression was examined utilizing a monoclonal antibody reactive with the Ia antigen framework. T cells were purified using monoclonal antibodies directed either at the entire T-cell population (OKT3) or the T-cell inducer subset (OKT4). By indirect immunofluorescence, it was shown that the human T-cell population contains no detectable Ia+ cells in the resting state. In contrast, in excess of 60% of the T-cell population expresses Ia antigen after alloactivation in the mixed lymphocyte culture. Moreover, these Ia antigens are expressed within both the OKT4+ and OKT4- subsets. Similarly, phytohemagglutinin and concanavalin A induced approximately 20% of peripheral T cells to express Ia antigen and the expression of these antigens is not restricted to either OKT4 subset. In contrast, only the inducer T-cell population which proliferates maximally to soluble antigen expresses Ia antigens after activation by tetanus toxoid. Thus, the expression of human Ia antigens on unique T-cell subsets depends upon the activation stimuli utilized and ability of the individual subset to respond to a given stimulus. Additional studies indicated that Ia antigens appear on previously Ia- T cells after activation and do not result from clonal expansion of a small subset of Ia+ T cells.
mesh_terms: D000937:Antigen-Antibody Reactions; D000954:Antigens, Surface / Q000032:analysis* / Q000235:genetics; D002999:Clone Cells / Q000276:immunology; D000939:Epitopes; D005802:Genes, MHC Class II; D006801:Humans; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000954:Antigens, Surface; D000939:Epitopes