1. To identify the critical events concerned with the processing of protein antigens, whereby membrane associated protein fragments capable of specific interaction with surface MHC molecules are generated from soluble native antigens. 2. To identify the signals which result in tolerance induction rather than clonal expansion, when autologous antigens coupled with self-MHC molecules are bound by T cells in the thymus or in culture. 3. To study the effects of immunoglobulin variable regions in the selection of the T cell repertoire during differentiation and immunization and the mechanism of this phenomenon. 4. To explore, in a murine model, the effects of the general activation of T cells, in vivo, with anti-TAP antibodies, or with conjugates of anti-TAP and anti-tumor antibodies on the rejection of experimental tumors, in the expectation that activated killer cells would be specifically directed to tumor targets in this model.