CD8⁺/DR⁺ T gamma cells inhibit the autologous mixed lymphocyte reaction

The proliferative response of T cells during autologous mixed lymphocyte reactions (AMLR) was affected by depletion of IgG Fc receptor⁺ T lymphocytes (Tg). Removal of Tg cells resulted in enhanced proliferation, and EA-rosette isolated Tg cells, when added to AMLR cultures as irradiated third components, reduced the uptake of ³H-thymidine by 63-87% in a dose-dependent manner. Negative selection using an avidin-biotin affinity chromatography technique demonstrated that the suppression was mediated by DR⁺ Tg cells; the major proportion of which also expressed the CD8 antigen. By comparing AMLR supernatants collected from control (lacking Tg) and suppressed (containing Tg) cultures on days 2, 3, and 4, it was established that supernatants from suppressed cultures had significantly reduced levels of cytokine activity. These data indicate that the CD8⁺/DR⁺ Tg cells function as suppressor cells during an AMLR and reduce the proliferative response by inhibiting AMLR responder T cells from producing the cytokines necessary for in vitro growth.