Paucity of functional T-cell memory to melanoma antigens in healthy donorsand melanoma patients

The functional characteristics of CD8+ T cells specific for melanoma antige ns (MAs) have often been defined after in vitro culture using nonprofession al antigen-presenting cells. We have examined CD8+ T-cell immunity to MAs a nd a viral antigen (influenza) in uncultured T cells of healthy donors and melanoma patients using autologous, mature, monocyte-derived dendritic cell s (DCs) pulsed with peptide antigens and viral vectors. Antigen-specific IF N-gamma -producing T cells reactive with HLA-A*0201-restricted peptides fro m four melanoma antigens (MelanA/MART-1, MAGE-3, tyrosinase, and gp100) wer e detected only at low frequencies (<30 per 2 x 10(5) peripheral blood mono nuclear cells for each of the Mils) from HLA-A2.1-positive healthy donors ( n = 12) and patients with stages III/IV melanoma (n = 8), Detection of MA-s pecific, but not influenza matrix peptide (Flu-MP)-specific, T cells requir ed a high concentration (10 <mu>g/ml) of the peptide in this assay. Further more, these T cells did not recognize endogenously processed antigen on tum or cell lines or cells infected with viral vectors capable of expressing MA s, The use of autologous, mature DCs led to a significant. increase in the number of Flu-MP, but not MA-specific, T cells in 16-h ELISPOT assays for b oth melanoma patients and healthy donors. In 1-week cocultures with DCs pul sed with 10 mug/ml peptide, MelanA/MART-1-specific T cells did not readily proliferate or differentiate into lytic effecters, in contrast to strong in fluenza-specific lytic responses. Therefore, despite distinct memory respon ses to influenza antigens, melanoma patients and healthy controls have a pa ucity of MA-reactive memory T cells, failing to rapidly generate IFN-gamma -secreting lytic effecters in shortterm assays, even when stimulated by DCs .