Effect of DCI and EGTA on anti-MHC I mAb OX18 enhanced cytolysis (A, 51Cr release) and apoptosis (B, DNA fragmentation) of CC531s cells by hepatic NK cells. CC531s cells were pretreated with mAb OX18 and hepatic NK cells were pretreated with DCI. EGTA was present during the coincubation. (A), Cytolysis was determined by a 18 hour 51Cr-release assay. (B), Apoptosis was determined by a 3 hour quantitative DNA fragmentation assay. The E:T ratio was 10:1. **p < 0.01 vs. the corresponding control (LSD test).