Effects of estradiol and progesterone on the priming effect. Normal neutrophils (1 × 10⁶ cells/mL) were incubated for 1 hour either with or without estradiol, progesterone, or both in combination (10^-8 g/mL), before the addition of LPS (1 μg/mL). Cells were then assessed for percentage apoptosis by propidium iodide DNA staining after 24 hours (A) or CD11b expression using a PE-labeled mAb after 6 hours and expressed as Ln mean channel fluorescence (B). □ indicates male (n = 6) and ▪ indicates female controls (n = 6). *P < .05 versus control. Error bars indicate mean ± SD.