Recognition of natural antigen NY-ESO-1 on tumour cell lines. In this assay, both NW-38 and MZ-Mel-19 (MZ19) are HLA-A2-positive and NY-ESO-1-positive, whereas LAR38 is HLA-A2-positive but NY-ESO-1-negative. T cells derived from VILs could recognise T2 cells pulsed with NY-ESO-1_157-165 peptides, as well as cultured melanoma cell lines. This recognition could be enhanced by IFN-gamma induction of tumour cells. Antigen-specific response was measured by intracellular IFN-gamma production (A) and by cytolytic capacity (B).