1989; Knuth, Wolfel et al. 1989; Topalian, Solo mon et al. 1989; Van den Eynde B 1989). Therefore, tumor specific antigens exist on metastatic human tumors, and are capable of stimulating a specific T cell response that can be expanded ex vivo to achieve clinical objective responses in tumor bearing patients. Endogenously synthesized antigens of virtually all mammalian cells are processed in an endoplasmic reticulum compartment and converted to small epitope peptides that ar e subsequently displayed on the cell surface in association with Class I MHC molecules to stimulate cytotoxic CD8+ cells (Townsend, Gotch et al. 1985; Maryanski, Pala et al.