Direct effect of PGE2 on NK-cell phenotype, cytotoxicity, and cytokine secretion. Freshly isolated NK cells were cultured for 24 hours in the presence of PGE2. (A) Phenotypic analysis of NK surface receptor expression. Filled histograms, NK cells without PGE2; bold lines, NK cells with 1000 ng/mL PGE2. Representative data of 1 of 6 different donors. (B) Flow cytometry–based NK-cell cytotoxicity assay against K562 by NK cells cultured with different concentrations of PGE2. Data shown are triplicates of 1 representative experiment of 4 different experiments. (C) IFN-γ production by NK cells cultured with different concentrations of PGE2 and stimulated for 16 hours with PMA and ionomycin, as evaluated by ELISA. Results are presented as mean + SEM and are obtained from 3 different donors. *P < .05.