Our laboratory is elucidating the nature of the immune response to tumors and establishing principles which may enhance our ability to immunize patients against known tumor antigens and induce tumor regression with cytokine therapy. We have developed methodologies for identifying tumor-specific CTL from patients with renal cell cancer and successfully used these techniques to identify an RCC-associated T-cell antigen. Unmutated FGF-5 was recognized in an HLA-A3 restricted fashion by RCC TIL from a patient showing spontaneous tumor regression). FGF-5 was expressed in 60% of RCC lines and in some other breast and prostate cancer lines which also were immunolgically recognized when transduced with HLA-A3. We have recently identified the HLA-A3-resticted epitope from FGF-5. It is generated by a novel protein splicing mechanism which juxtaposes two remote 4 and 5-amino acid fragents to reconstitute the 9-mer peptide recognized by the CTL. HLA-A2 restricted CTL that recognize FGF-5 and antigen-positive A2+ RCC have also been generated from a patient with RCC and the epitope identified. Ongoing efforts are directed at modifying these native epitopes to improve their immunogenicity and we have initiated a clinical protocol vaccinating patients with the HLA-A2 and HLA-A3 native peptides. Our previous studies have indentified means for consistently generating RCC reactive CD8+ and CD4+ T-cells from patients with RCC. This has led to the opportunity to pursue new antigen identification for an adenocarcinoma, a much needed development in the field of immunotherapy. In particular, MHC Class II-restricted recognition has been under-studied and this presents an opportunity to decern the role of CD4 cells in tumor rejection in patients. To pursue this, we are developing and refining the methods for cloning these antigens to address the particulars of Class II presentation. In addition, we are pursuing way to adapt clinical vaccine effort to the generation of large numbers of tumor-reactive T-cells (both CD4 and CD8) for clinical administration.