A HUMAN-MELANOMA CELL-LINE, RECOGNIZED BY BOTH HLA CLASS-I AND CLASS-II RESTRICTED T-CELLS, IS CAPABLE OF INITIATING BOTH PRIMARY AND SECONDARY IMMUNE-RESPONSES

We have characterized a melanoma cell line, FM3, established from a me tastasis of a 75 year old female patient (HLA-A2, HLA-DQ7) with malign ant melanoma. This cell line expresses both HLA class I and class II a ntigens, as well as several important accessory molecules at high leve ls. FM3 cells were shown to function as a stimulator of both allogenei c as well as autologous mixed lymphocyte tumour cell culture (MLTC). F rom these autologous MLTC we were able to generate cytotoxic T cell cl ones indicating that FM3 is capable of processing and presenting endog enous antigens. We have used this cell line in a model system to inves tigate whether these cells were able to initiate and support an immune response with specificity for selected peptide antigens. The FM3 cell line was capable of presenting a HLA-DQ7 restricted ras derived pepti de (5-21, 13Gly-->Asp) to a previously established T cell clone, RM70. The ability of FM3 to function as an antigen presenting cell (APC) wa s comparable to that of an autologous Epstein Barr virus (EBV) transfo rmed B cell line. The CD4(+) T cell clone RM70 showed a peptide-specif ic anti-proliferative effect on FM3 cells. This growth inhibition was not due to cytotoxicity as measured in a standard 4h chromium release assay. The FM3 cell line also presented a HLA-A2 restricted nonapeptid e derived from the influenza matrix protein, M1(58-66) to a CD8(+) T c ell line specific for this peptide. This resulted in an effective kill ing of the melanoma cells. Together, these data suggest that some mela nomas may initiate an immune response by presenting their own specific antigens in an immunogenic context, and subsequently serve as targets for T cells of both the CD4(+) and CD8(+) phenotype.