Ia determinants on stimulated human T lymphocytes. Occurrence on mitogen- and antigen-activated T cells.

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Abstract
Human T[thymus-derived]-cell blasts were generated by stimulation with mitogens and antigens. A proportion of these blasts expressed Ia [immune response-associated] antigens detectable by immunofluorescence with allo- and hetero-antiserums. The maximal expression of Ia antigens was delayed and usually occurred after the peak of blastogenesis. Among the 3 mitogens used, pokeweed mitogen (PWM) was most effective in giving a high percentage and intense Ia staining of T cell blasts. Phytohemagglutinin and concanavalin A blasts gave weaker and lower percentages of Ia staining. Activation by alloantigens and soluble antigens such as tetanus toxoid and purified protein derivative resulted in Ia expression on T cells comparable to PWM stimulation. Depletion of Ia+ cells from freshly isolated T cells with anti-Ia and complement decreased subsequent Ia expression, suggesting that a proportion of Ia+ blasts were derived from Ia-bearing peripheral blood T cells. When the specificities of the Ia antigens on T cell blasts were examined with alloantiserums, it was evident that the T blasts expressed similar HLA-DR determinants to those on B [bone marrow-derived] cells from the same donor; occasional minor differences between stimulated T cells and autologous B cell lines or fresh B cells were encountered.

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