/, EFFECTS OF ANTIBODIES TO MEMBRANE ANTIGENS

The mechanisms by which cells become activated and interact to produce immune responses have not been clearly defined. Cell surface molecules are thought to play a role in these events but the relevant molecules for the expression of many immune functions have not been identified. Thus, the major goal of this study was to apply a method of analysis, perturbation of membrane antigens by specific antibody, with the potential for identifying molecules relevant to function, to several major surface molecules of cells participating in in vitro models of immune function. The results of these studies indicated that the presence of antibody to the Thy 1 molecule could inhibit generation of murine cytotoxic T lymphocytes in some cases but not others. It was also shown that antibody to another murine cell surface molecule, T200, could modulate and ultimately suppress the proliferative response to alloantigen as well as the generation of cytotoxic T cells. The suppressive effects were seen when antibody was added either at the initiation of culture or at various times after initiation. These effects were shown to be unique to antibody interaction with the T200 molecule since antibodies to other cell surface molecules either had no effect or suppressed with different kinetics. The antibody alone was not mitogenic for murine splenocytes but could enhance the mitogenic effect of the plant lectin, concanavalin A. Antibodies to an allotypic determinant on the T200 molecule, Ly 5.1, also had suppressive effects on proliferation and generation of cytotoxicity. In sum, these results contribute to the body of evidence suggesting that activation and interactive events leading to immune function may require the participation of several major cell surface molecules, possibly through formation of membrane complexes