The overall goal of this project is to investigate structure-function relationships of cell-surface membrane components on cytotoxic T lymphocytes (CTL). This objective is being approached by the production of monoclonal antibodies against functional membrane determinants on CTL. Immunization procedures in syngeneic recipients are focused at killing-relevant membrane determinants on CTL by pre-immunization with syngeneic helper T cells and cyclophosphamide. Functionally inhibitory monoclonal antibodies will be evaluated and compared for: (1)\blocking activity and (2)\target membrane structures using both in vitro-\and in vivo-generated CTL. Cloned CTL, which have suffered the loss of specific recognition and/or cytolytic potential, have been isolated and maintained as "stable" variants. These variants will be used as an important panel of target cells to determine which membrane moieties contribute to the multistep lytic cycle of CTL. (CS)