In this proposal, we outline experiments to continue our analysis of the cellular and molecular requirements for the generation and expression of cell-mediated cytotoxicity. Our principal working system continues to be the mixed leukocyte culture. We will also examine the requirements for generaton and expression of cytotoxic effector memory. With respect to the latter, we will examine the involvement of Ly phenotypes both in the initial generation of memory, and in the regeneration of cytotoxic function by alloantigen. We also propose an in depth analysis of the role of membrane structure and membrane fluidity in cell-mediated immune reactions. A system for controlled manipulation of the fatty acid composition (and hence the fluidity) of membrane phosphatides has been successfully adapted to lymphoid cells. A variety of biological and immunological functions of altered cells will be examined, including lectin binding, patching behavior, generation of cytotoxic function, and expression of cell-mediated cytotoxic function. Finally, we propose to study the process of cytolysis itself through the use of synthetic lipid vesicles into which is inserted M13 phage coat proteins. We will specifically study antibody-dependent cell-mediated cytotoxicity.