Polymeric Immunoglobulin Receptor is synthesized locally in the rodent vagina and under the control of sex hormones

The aim of this study was to identify the origin of Polymeric Immunoglobulin Receptor (plgR) present in the vagina and to examine the control by sex hormones of vaginal plgR levels. PlgR message corresponding in size to that previously reported in liver and uterus was detected by Northern blot analysis of total RNA from vagina. When levels of plgR mRNA were examined in the vagina at different stages of the estrous cycle, message levels were highest diestrus and very low at estrus and proestms. Immunohistochemical analysis of plgR in the vagina indicated that the protein expression corresponds with the mRNA levels and was confined to superficial layers of squamous epithelium at diestrus. In situ hybridization studies showed that plgR is synthesized by the superficial squamous epithelial layers only at diestrus, no message was detected in these cells at estrus. When ovariectomized animals were treated with estradiol and/or progesterone for 3 days, plgR mRNA levels were significantly reduced in estradiol-treated animals compared to saline controls. No significant changes in mRNA levels were seen in progesterone- treated animals, progesterone did not reverse the inhibitory effect of estradiol on plgR mRNA levels. Immunohistochemical analysis indicated that plgR levels paralleled mRNA levels in the vagina of hormonally treated rats. These findings have important implications with regard to the presence of mucosal immunity which facilitates fertilization and defends against infection in the rodent vagina during the estrous cycle. Supported by AI-13541 from NIH.