Suppression of anti-Candida activity of murine neutrophils by progesterone in vitro: a possible mechanism in pregnant women's vulnerability to vaginal candidiasis.

Sex steroid hormones were examined for their effect on mycelial growth of Candida albicans, and the inhibitory activity of casein-induced murine peritoneal neutrophils against mycelial growth of C. albicans was examined in vitro using a crystal violet staining method or a [3H]glucose incorporation method. Four steroid hormones, danazol, estradiol, estriol and testosterone had no effect on mycelial growth of C. albicans, but progesterone appeared to convert the growth form of C. albicans from hyphal to yeast. Danazol (10(-6) M) and progesterone (10(-5) M) suppressed anti-Candida activity of neutrophils of non-treated mice, while testosterone, estradiol, and estriol did not. The anti-Candida activity of neutrophils of estradiol-pretreated mice was clearly suppressed by progesterone even at 10(-6) M which corresponded to its plasma concentration in pregnant women in the third trimester. The physiological significance of this suppressive effect of progesterone was discussed in relation to the vulnerability of pregnant women to vaginal candidiasis.