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

TLDR

T‑cell blasts were produced by stimulating cells with mitogens and antigens. Stimulation of T cells with mitogens or antigens induced Ia antigen expression on a subset of blasts, with maximal expression delayed after peak blastogenesis; pokeweed mitogen produced the strongest Ia staining, while other mitogens and alloantigen activation yielded weaker staining, and depletion of Ia⁺ cells reduced subsequent Ia expression, indicating that Ia⁺ blasts arise from Ia‑bearing peripheral blood T cells and that their Ia determinants resemble those on autologous B cells.

Abstract

Human T-cell blasts were generated by stimulation with mitogens and antigens. A proportion of these blasts expressed Ia antigens detectable by immunofluorescence with both allo- and hetero-antiserums. The maximal expression of Ia antigens was delayed and usually occurred after the peak of blastogenesis. Among the three 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 cells from the same donor; occasional minor differences between stimulated T cells and autologous B-cell lines or fresh B cells were encountered.