The T4 molecule differentially regulating the activation of subpopulations of T4⁺ cells

It has been demonstrated that the T4⁺2H4⁺ subset functioned as a suppressor inducer cell, whereas the reciprocal T4⁺2H4^- subset provided help for B cell Ig production. In the present studies, a series of monoclonal antibodies to cell surface structures expressed on subsets of cells were examined for their effects on the proliferative and immunoregulatory functions generated in AMLR. We demonstrated that anti-T4 antibody preferentialy inhibited the proliferative response of the T4⁺2H4⁺ but not T4⁺2H4^- cells against self-MHC antigens. In contrast, anti-T3 and anti-Ia antibodies inhibited the response of both subsets of cells. This subset preference of anti-T4 antibody was not attributable to either the isolation procedures used or a shift in the kinetics of proliferation to autologous self-MHC antigens. Moreover, both IL 2 production and the immunoregulatory function of the T4⁺2H4⁺ subset was profoundly inhibited by anti-T4 antibody, whereas the T4⁺2H4^- subset was minimally influenced. In the absence of Ia molecules, T4⁺2H4⁺ but not T4⁺2H4^- cell proliferation was inhibited with anti-T4 antibody. Together, these results suggest that the T4 molecule plays a distinct functional role in the differential triggering of subsets of T4⁺ cells.