Effects of estradiol and progesterone on Fas-induced apoptosis and Fas receptor expression. Neutrophils were incubated with estradiol, progesterone, or both (10^-8 g/mL) for 6 hours. (A) Fas antibody was added and the percentage apoptosis assessed at 24 hours by propidium iodide staining and flow cytometry. □ indicates male (n = 10) and ▪ indicates female (n = 10). (B) Neutrophils were incubated with Fas antibody and mean channel fluorescence (LnMCF) was subsequently assessed by flow cytometry. □ indicates male (n = 5) and ▪ indicates female (n = 5). Error bars indicate mean ± SD.