Identification of the presenting HLA molecules and of the gene encoding the antigenic peptide. COS-7 cells were transiently transfected by the DEAE-dextran method with 50 ng of HLA-Cw*1601 cDNA and 50 ng of cDNA GEP 3/317/2B7, which was isolated from a cDNA library screened with CTL 82/21. Each cDNA was inserted into pCD-SRalpha. After 24 h, 1,500 CTLs were added to the transfected cells. TNF production was measured 24 h later.