Immunoprotection of gonads and genital tracts in human embryos and fetuses: immunohistochemical study

The immune protection of genital organs in embryogenesis has not been sufficiently studied. The purpose of this study was to investigate the development of the secretory immune system (SIS) in the gonads and genital tracts of human embryos and fetuses.

Developing gonads at different stages and genital tracts from 18 embryos and 39 fetuses in the first to third trimester of gestation were analyzed for presence of different component of SIS: secretory component (SC), joining (J) chain. IgA, IgM, IgG, macrophages, and subsets of lymphocytes. The material was divided into two groups: cases not subjected to foreign antigenic effects (group I, n = 31) and those under antigenic attack (chorioamnionitis, group II, n = 26).

In embryos and fetuses of group I, SC, J chain, and IgG were seen in the epithelium of mesonephric and paramesonephric ducts, proliferating coelomic epithelium, epithelium of the uterine tubes and uterus, epithelium of the vas deferens, epididymis, and rete testis. IgA and IgM appeared in 6-week-old embryos. J chain, IgA, IgM, and IgG, but not SC, were found in the primary oocytes and oogonia, spermatogonia. and interstitial cells. An abundance of macrophages was seen in 4-week-old embryos. T and B lymphocytes first appeared in 6-7-week-old embryos. In embryos and fetuses of group II, reactivity of immunoglobulins (Igs) decreased until they disappeared altogether.

Components of SIS were seen in genital organs in 4-5-week-old embryos and were present during the whole intrauterine period. We suggest the presence of two forms of immune protection of fetal genital organs. One form contains SC, J chain, and Igs and is present in the genital tract epithelium. The second form contains only J chain and Igs and is present in germ cells of gonads. The loss of Igs in cases with chorioamnionitis reflects the functional participation of the SIS of genital organs in response to antigen attack.