Ia determinants on human T-cell subsets defined by monoclonal antibody. Activation stimuli required for expression.

• DOI: 10.1084/jem.150.6.1472
• Publication Date: 2004-06-23T21:00:50Z
• Authors: E L Reinherz; P C Kung; J M Pesando; J Ritz; G Goldstein; S F Schlossman
• Keywords: Antigen-Antibody Reactions; 0301 basic medicine; Epitopes; 03 medical and health sciences; T-Lymphocytes; Antigens, Surface; Genes, MHC Class II; Humans; Lymphocyte Activation; Clone Cells; 3. Good health

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.