CTL recognition of HA-1^neg tumor cells after 5-AZA-CdR treatment. (A) HA-1^pos and HA-1^neg tumor cells and fibroblasts (all HLA-A2^pos) were treated with 100 μM 5-AZA-CdR for 8 days. Depicted is the response of the HA-1^H–specific CTL clones 2.12 and 3HA15 and the H-Y–specific CTL clone 21-17 toward target cells before and after treatment with 5-AZA-CdR; y-axis indicates number of interferon-γ spots in the ELISPOT analysis per 5 × 10³ cells. (B) Depicted are representative examples of the ELISPOT wells on coincubation of MDA-MB 231, 518A2, and Fib01 cells with the HA-1 CTL clone 2.12 and the H-Y CTL clone 21-17 before and after treatment with 5-AZA-CdR. (C) 518A2 tumor cells were treated with 1 μM 5-AZA-CdR for 8 days. Depicted is the lysis of 518A2 tumor cells by the HA-1^H–specific CTL clone 3HA15 and the HLA-A2–specific CTL clone 1E2 before and after treatment with 1 μM 5-AZA-CdR for 8 days in a chromium release assay; x-axis indicates mean percentage of specific lysis (2 measurements per condition); y-axis, CTL clones each in 2 different effector/target ratios.