Tumor infiltrating lymphocytes are currently under investigation in Surgery Branch clinical protocols for the adoptive immunotherapy of patients with advanced cancers. Responses to therapy have been observed in select patients with melanoma. In vitro studies have shown that melanoma TIL are T cells which can specifically recognize autologous tumor. Identifying tumor Ag and mechanisms by which TIL destroy tumor is essential to optimizing current clinical protocols and devising new therapeutic strategies. Areas of study are: 1. Isolation of a melanoma-specific Ag recognized by TIL. A melanoma tumor line resistant to TIL lysis has been immunoselected from a TIL-Bensitive melanoma. A subtracted cDNA library has been prepared from these two tumor lines and transfected into the TIL-resistant tumor. TIL lysis is being used to screen for positive transfectants, preliminary to isolating a gene coding for the relevant tumor Ag in this system. 2. Multiplicity and distribution of melanoma-specific Ag. Melanoma-specific cytolytic TIL were used to screen HLA-matched tumors for the presence of specific Ag. Some Ag were broadly expressed among many melanomas while others had more limited expression. Multiple HLA-A, B, C determinants could function in Ag recognition. 3. Specific cytokine release by TIL in response to autologous tumor. Studies have shown that 18/30 melanoma TIL as well as 3/12 breast carcinoma TIL cultures secreted TNF-alpha, GM-CSF, and/or IFN-g specifically on contact with autologous or some HLA-matched tumors. CD8+ as well as CD4+ T cells were capable of secretion. We are currently studying this phenomenon as a possible predictor of therapeutic response.