Background: Although intraepithelial lymphocytes (IELs) in human oviductal epithelium have been implicated in the regulation of local immunity, the precise kinetics and mechanism of steroid regulation of IEL are largely unknown.
Methods: We examined the localization of estrogen receptors (ERs) and progesterone receptors (PRs) in 41 human oviducts by immunohistochemistry. These tissues were obtained from various menstrual cycles, also from both post-menopausal women and tubal pregnancies. The expressions of ERbeta mRNA and membrane (m)PR mRNA were examined by in situ hybridization and RT-PCR, respectively.
Results: Most of the IEL expressed ERbeta at both mRNA and protein levels. The number of ERbeta-positive IEL, which were identified as CD8-positive T lymphocytes and also were mPR positive, was increased in the late proliferative, the mid-secretory and late secretory phases in normally cycling women (P < 0.05). Interestingly, in tubal pregnancy, ERbeta-positive IELs were consistently abundant. In addition, we found a high Ki-67-labelling index for IEL, although ERalpha was entirely absent in the tubal pregnancy oviducts.
Conclusions: These results suggest that the number of IEL fluctuated because of estrogen and progesterone levels probably through ERbeta and mPR, respectively. ERbeta-positive IEL may be involved in regulating immune tolerance in tubal pregnancy oviducts.