DIVERSITY OF THE CYTOTOXIC MELANOMA-SPECIFIC IMMUNE-RESPONSE - SOME CTL CLONES RECOGNIZE AUTOLOGOUS FRESH TUMOR-CELLS AND NOT TUMOR-CELL LINES

In the present work, to analyze the heterogeneity of the tumor-specifi c cytotoxic immune response, a large number of T cell clones were gene rated from the infiltrate of a tumor-proximal invaded lymph node, and two kinds of melanoma-specific CD8(+) CTL clones were derived. The maj ority of T cell clones (about a hundred) are characterized by a specif ic lysis of the autologous tumor cell lines. Among 34 of the latter cl ones, HLA-A2 molecule and MART-1(27-35) peptide have been shown to pla y a predominant role in tumor recognition. However, no significant amp lification at the tumor site was observed for 3 of these CTL. The othe r kind of tumor-specific CTL (1 oligoclonal and 2 clonal cell lines) d id not lyse the autologous melanoma cell lines but lysed the ''fresh'' autologous tumor cells in a MHC class I-dependent manner. Functional analysis of the two different CTL clones have shown that they did not lyse NK targets, autologous peripheral monocytes, activated T cells, a nd transformed B cells or any of the few allogeneic cultured and uncul tured melanoma cells we tested. TCR repertoire analysis has shown that one of these CTL clones was significantly detectable ''in situ'' amon g tumor-infiltrating lymphocytes, while not detectable among PBMC. Suc h melanoma-specific lymphocytes, which could not have been picked out through conventional screening procedures using tumor cell lines, coul d potentially play a role in tumor rejection. These results suggest th at the immune response analyzed toward melanoma cell lines does not to tally reflect the in situ immune status.