Lymphatics, intraepithelial lymphocytes and endometrial lymphoid tissues in the rabbit uterus: an electron microscopic and immunohistological study.

Rabbit uterine intraepithelial lymphocytes, endometrial lymphoid aggregates and lymphatic capillaries were examined electron-microscopically and immunohistochemically at well-defined intervals after the injection of human chorionic gonadotropin (hCG). Lymphatic capillaries originated near the bases of the glands in the uterine cervix and in the border zone between the lamina propria mucosae and myometrium in the uterine body. The lymphatic capillaries were maximally dilated, and their endothelial cells were thinnest 8 hours after hCG injection. Patent junctions between the adjacent endothelial cells of lymphatics in the uterine body were observed in good accordance with the appearance of stromal edema and lymphatic dilatation. The numbers of intraepithelial lymphocytes and macrophages changed cyclically after the induction of ovulation. They were highest 11 hours after hCG injection when lymphocytes were seen occasionally in the lumens of lymphatics located in the lamina propria mucosae of the uterine body. Most of the intraepithelial and interstitial lymphocytes were cells labeled with T cell serum but some were labeled with IgA serum and were occasionally seen beneath the epithelium. Lymphoid aggregates were uniformly present in the stratum basalis and consisted of lymphocytes and macrophages. They had no germinal centers, surrounding lymphatics or high endothelial venules (HEV). The results suggest that lymphatic capillaries are the main route for the removal of edema fluid and for migratory lymphoid cells in the rabbit uterus.