DISTRIBUTION OF AUTOLOGOUS TUMOR-SPECIFIC CYTOTOXIC T LYMPHOCYTES IN HUMAN METASTATIC MELANOMA

The study of specific immunity in human cancers has been hampered by the elusive distribution and heterogeneity of effector cells. In this study, we have investigated the distribution of autologous melanoma-specific cytotoxic T lymphocytes (CTLs) in 18 different distant metastases from melanomas (9 non-visceral and 9 visceral metastases). Uncultured cells from tumors were provided directly for the establishment of T-cell clones using limiting dilution analysis to avoid any possible effects of in vitro sensitization of T cells to coexisting tumor cells. Autologous tumor-specific CTL clones were detected in 6 of 18 tumors (33%, 4 non-visceral and 2 visceral metastases). The majority of CTL clones (35 of 46 and 17 of 19) in 2 patients with HLA class-I A2 haplotype failed to lyse either A2+ or A2- allogeneic melanoma cells, although anti-class-I (monornorphic) MAb inhibited their cytotoxicity. The remaining 11 of 46 and 2 of 19 CTL clones showed A2-restricted cytotoxicity. Autologous tumor-specific cytotoxicity was also detected after polyclonal culture of these tumor-infiltrating lymphocytes (TILs) in 8 of 16 tumors (50%, 5 non-visceral and 3 visceral metastases). These results suggest that tumor-specific T cells exist at tumor sites in at least one-third of distant metastases of melanomas and could be induced by the addition of IL-2 in at least half of the tumors. Tumor-specific T cells were detectable more often in non-visceral than in visceral metastases.