Our experiments show that co-cultivation of the melanoma UKRV-Mel-15a and Ma-Mel-63a cells with Melan-A/MART-126-35 CTL led in both instances to the isolation of several melanoma cell clones, which revealed impaired presentation of the Melan-A/MART-126-35 antigenic peptide (Figs 1 and 6). The gene discussed is MLANA; the disease is melanoma.