Inhibitory effect of a low dose of prednisone on PHA-induced Ia antigen expression by human T cells and on proliferation of T cells stimulated with autologous PHA-T cells

Administration of a small dose of prednisone markedly reduced (1) the PHA-induced expression of Ia antigens by T cells, (2) the stimulatory activity of Ia antigen-bearing T cells in autologous and allogeneic mixed lymphocyte reactions (MLRs), and (3) the proliferative response of T cells stimulated with autologous PHA-activated T cells or autologous or allogeneic non-T cells. The inhibitory effects of prednisone are reversible and are not detectable on T cells isolated from blood drawn 24 hr following prednisone administration. The kinetics of the prednisone-mediated inhibition of MLRs with autologous PHA-T cells is different from that of MLRs with autologous non-T cells. These data in conjunction with the information available in the literature suggest that the mechanisms underlying these two types of autologous MLRs are different.