Melanoma patients were injected with various vaccines containing a MAGE-A3 peptide presented by HLA-DP4. Anti-MAGE-A3.DP4 T cells were not detectable in the blood before vaccination, but their frequencies after vaccination ranged from 2 Â 10 À6 to 2 Â 10 À3 among the CD4 + blood T lymphocytes of the patients. The CD4 + blood T lymphocytes that stained ex vivo with HLA-DP4 tetramers folded with the MAGE-A3 peptide were selected by flow cytometry and amplified under clonal conditions. About 5% of the CD4 + T-cell clones that recognized the MAGE-A3.DP4 antigen had a CD25 + phenotype in the resting state. These CD25 + clones had a high capacity to suppress the proliferation of another T-cell clone after peptide stimulation in vitro. Most of them had high FOXP3 expression in the resting state and an unmethylated FOXP3 intron 1. They produced active transforming growth factor-B but none of cytokines IFN-;, interleukin-2 (IL-2), IL-4, IL-5, and IL-10. About 20% of CD25 À clones had a significant but lower suppressive activity. Most of the CD25 À clonal populations contained cells that expressed FOXP3 in the resting state, but FOXP3 demethylation was not observed. We conclude that MAGE-A3.DP4 vaccination can produce CD4 + T cells that may exert regulatory T-cell function in vivo.

We report that melanoma cell lines expressing the interleukin-1 receptor exhibit 4-to 10-fold lower levels of mRNA of microphthalmia-associated transcription factor (MITF-M) when treated with interleukin-1b. This effect is NF-jB and JNKdependent. MITF-M regulates the expression of melanocyte differentiation genes such as MLANA, tyrosinase and gp100, which encode antigens recognized on melanoma cells by autologous cytolytic T lymphocytes. Accordingly, treating some melanoma cells with IL-1b reduced by 40-100% their ability to activate such antimelanoma cytolytic T lymphocytes. Finally, we observed large amounts of biologically active IL-1a or IL-1b secreted by two melanoma cell lines that did not express MITF-M, suggesting an autocrine MITF-M downregulation. We estimate that~13% of melanoma cell lines are MITF-M-negative and secrete IL-1 cytokines. These results indicate that the repression of melanocyte-differentiation genes by IL-1 produced by stromal cells or by tumor cells themselves may represent an additional mechanism of melanoma immune escape.