Induction of suppression following autologous mixed lymphocyte reaction; role of a novel 2H4 antigen

In this study, we have investigated the cellular and molecular basis for immunoregulatory function of T4⁺ cells after autologous mixed lymphocyte reaction (AMLR) activation. We demonstrated that the T4⁺2H4⁺ subset but not the T4⁺2H4⁻ subset can proliferate maximally in response to autologous non‐T cells. T4⁺ cells activated by AMLR exerted suppressor activity on pokeweed mitogen‐driven IgG synthesis of autologous peripheral blood lymphocytes. The suppressor activity by AMLR‐activated T4⁺ cells required the presence of fresh T8⁺ cells in the secondary culture, indicating that AMLR‐activated T4⁺ cells functioned as a suppressor inducer rather than as a suppressor effector population. Following activation of T4⁺ cells in AMLR, it is the T4⁺2H4⁺ subset which induces suppression through the T8 population. Moreover, the treatment of AMLR‐activated T4⁺2H4⁺ cells with anti‐2H4 antibody, but not other antibodies, resulted in the abolishment of suppressor inducer function of such cells, suggesting that the 2H4 molecule itself may be involved in the suppressor inducer function. The 2H4 antigen on such cells was shown to be comprised of 220‐kDa and 200‐kDa glycoproteins. These results support the notion that the AMLR may play an important role in generating suppressor inducer signals and in down‐regulating the immune response following self major histocompatibility complex recognition. More importantly, the present studies indicate that the 2H4 antigen on T4 cells serves not only as a phenotypic marker of suppressor inducer cells, but may have a functionally important role itself in inducing suppression.