Specificity in the immune system is dictated and regulated by specific recognition of peptide/major histocompatibility complex (MHC) complexes by the T cell receptor. Such peptide/MHC complexes are a desirable target for novel approaches in immunotherapy because of their highly restricted fine specificity. Expression of specific peptides in complex with MHC class I molecules on cells was shown to be associated with cancer and autoimmune disorders (1 –8 ). For example, human melanomas express tumor-specific peptides that are presented to the immune