Immunocompetent cells in the endometrium of fetuses and children.

BACKGROUND Although the immunocompetent cells of the adult human endometrium are well characterized, there is little information about these cells in the developing uterus. This study was undertaken to investigate the distribution of leukocyte subpopulations in the endometrium of fetuses and children. METHODS Uterine tissue obtained at autopsy from fetuses (n = 11) and neonates/children (n = 9) between 17 weeks gestation and 5(1/2) years of age was investigated with antibodies against various leukocyte subsets by immunohistochemical staining techniques. RESULTS The densities of CD45+ and CD68+ cells were significantly higher in the endometrium of neonates/children than in that of fetuses. CD14+ monocytes represented the largest leukocyte subpopulation in both groups. CD56+ natural killer cells and HLA-DR+ antigen-presenting cells were absent from fetal endometrium. There were no differences in density of CD3+ T cells between the two groups, but CD4+ T helper cells were found only in fetal endometrium. CONCLUSIONS The endometrial leukocyte population of fetuses and small children is different from that seen in adult women. The appearance of CD56+ and HLA-DR+ cells in endometrium seems to be a post-natal event, which may be induced by the changes in hormone levels and/or the adaptation of the local immune system to the changing microenvironment.