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

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Abstract
We have characterized a melanoma cell line, FM3, established from a metastasis of a 75 year old female patient (HLA-A2, HLA-DQ7) with malignant melanoma. This cell line expresses both HLA class I and class II antigens, as well as several important accessory molecules at high levels. FM3 cells were shown to function as a stimulator of both allogeneic as well as autologous mixed lymphocyte tumour cell culture (MLTC). From these autologous MLTC we were able to generate cytotoxic T cell clones indicating that FM3 is capable of processing and presenting endogenous antigens. We have used this cell line in a model system to investigate 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 peptide (5-21, 13Gly- >Asp) to a previously established T cell clone, RM70. The ability of FM3 to function as an antigen presenting cell (APC) was comparable to that of an autologous Epstein Barr virus (EBV) transformed B cell line. The CD4+ T cell clone RM70 showed a peptide-specific anti-proliferative effect on FM3 cells. This growth inhibition was not due to cytotoxicity as measured in a standard 4 h chromium release assay. The FM3 cell line also presented a HLA-A2 restricted nonapeptide derived from the influenza matrix protein, M1(58-66) to a CD8+ T cell line specific for this peptide. This resulted in an effective killing of the melanoma cells. Together, these data suggest that some melanomas 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.