Overview of the strategy used to identify the antigenic peptide. The MAGE-6 cDNA is shown in the upper part of the figure with the three exons appearing as open boxes and the open reading frame as a black box. The MAGE-6 cDNA isolated from the library, GEP3/317/2B7, and truncated cDNA constructs were cotransfected into COS-7 cells together with an HLA-Cw*1601 cDNA. The transfected cells were tested for recognition by the CTLs. Three long peptides (underlined) were synthesized on the basis of the sequence of the region coding for the antigenic peptide, and tested for recognition by the CTLs. A 12 amino acid-long peptide tested positive and shorter peptides were subsequently tested. The shortest peptide recognized by CTL 82/21 is boxed.