Frequency and relative fraction of tumor antigen-specific T cells among lymphocytes from melanoma-invaded lymph nodes

Several tumor antigens have been described as candidates for immunotherapy. Our study compared HLA-A2-restricted epitopes from 5 antigens commonly expressed by melanomas, i.e., Melan-A/MART-1 peptides (26-35 and 27-35), tyrosinase (368-376), gp-100 (280-288), MAGE-3 (271-279) and NA17-A (1-10), for their relative capacity to promote the development of cytotoxic and cytokine-producing specific CD8+ lymphocytes within melanoma-invaded lymph nodes. We used short-term cultured melanoma-invaded lymph node lymphocytes (MILLs) and tested responses developed by these cells to peptide-pulsed TAP-deficient T2 cells. We measured both the lytic response developed by MILLs and the fraction of these cells that secreted interferon-gamma (IFN-gamma), as deduced from intracellular cytokine labeling. Reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze the expression of the 5 antigens within melanoma-invaded lymph nodes. Melan-A/MART-1, tyrosinase and gp-100 peptides were recognized by MILLs derived, respectively, from 8 of 20, 5 of 19 and 4 of 20 melanoma-invaded lymph nodes expressing these antigens. Most MILLs specific for Melan-A/MART-1 and tyrosinase exhibited both lysis and IFN-gamma responses, whereas most of those specific for gp-100 developed only lysis. Weak lysis without IFN-gamma secretion was developed against NA17-A and MAGE-3 peptides by MILLs from, respectively, 3 of 9 and 2 of 14 lymph nodes expressing these antigens. Our data show a prevalence of both cytotoxic and IFN-gamma-secreting effector T cells specific for differentiation antigens within HLA-A2 melanoma-invaded lymph nodes, which makes these antigens attractive targets for specific immunotherapy.