Effects of inhibitors of bacterial and host cell metabolism on induction of susceptibility to lysis by NK cells. The increase in lysis of CT-infected versus mock infected SiHa cells (Δ percentage lysis) by NK cells, untreated after infection (nil) or following treatment with penicillin G, rifampicin, or cycloheximide. Results using an effector : target ratio of 20 : 1 are shown. Differences between levels of lysis of CT-infected and mock-infected cells are significant for untreated (P < 0·002), penicillin-treated (P < 0·005) and cycloheximide-treated (P < 0·02) cells, but not for rifampicin-treated cells (P = 0·34). Significance was tested using Student's two-tailed t-test.