Blockade of CD94/NKG2A inhibitory receptors restores killing of IFN-γ–treated OVACs. The effect of anti-CD56 (MOC-1) or anti-CD94 (HP3D9) mAb’s on the IFN-γ–mediated protection of OVACs was evaluated in the following situations: The HLA-A11⁺ OVAC 16 was used as target for the HLA-A11–specific T cell clone KV109 (a) and for the IVT-specific T cell clone BK289 (b). The peptide concentration in b was 1 μg/ml. Recognition of unpulsed targets by BK289 was below 5% and is not shown. (c) The HLA class I–restricted, tumor-reactive CTL line RF1 was used as an effector against untreated and IFN-γ–treated OVAC 19. (d) Reactivity of TAL 31 against autologous OVAC 31. Error bars represent SD of triplicate cultures. *P < 0.05, **P < 0.01 as determined by two-tailed Student t test.