Lymphatics and lymphoid tissue of the fallopian tube: Immunoelectronmicroscopic study

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Abstract
Lymphoid tissue of the human fallopian tube consists of follicles, lymphoepithelium, and lymphatic and blood capillaries and is located consistently in the interstitial part of the‐human fallopian tube. Using an immunoelectronmicroscopic technique, we have elucidated the ultrastructure of the lymphoid tissue of the human fallopian tube and the fine distribution and ultrastructure of the lymphatics associated with the rabbit fallopian tube. Lymphatic capillaries arise in the lamina propria mucosa and the periphery of follicles, where they are sparsely distributed, run through the muscular layer, and form a dense network in the subserosa. Characteristic features of the ultrastructure are aggregations of smooth muscle cells, alternating areas of densely and sparsely distributed collagen fibers, and unmyelinated nerve fibers beneath the lymphatic endothelium.Immunoelectronmicroscopic analysis has demonstrated an obvious difference in the distribution of T‐ and B‐lymphocytes in the lymphoid tissue of the human fallopian tube. Many T‐lymphocytes are present in the follicles and epithelium, but B‐lymphocytes are either absent or rarely found. T‐lymphocytes sometimes infiltrate into the basal lamina of the epithelium lying in close contact with the follicles.We conclude that the lymphoid tissue is constantly located in the interstitial part of the human fallopian tube and that intraepithelial lymphocytes, mainly T‐lymphocytes, migrate via the basal lamina of the epithelium from follicles. Lymphatic capillaries in the fallopian tube may be the main migratory route of intraepithelial lymphocytes.The intraepithelial lymphocytes and epithelial cells of the fallopian tube have attracted considerable interest as a result of immunological studies of the recognition of spermatozoal antigens and the fertilized ovum. The only previous anatomical investigator to report the presence of the lymphoid tissue of the human fallopian tube was Uchida (1953), whereas more recent studies have shown that the intraepithelial lymphocytes and epithelial cells of the fallopian tube are related to the mucosal‐associated lymphoid tissue (MALT) (Geppert et al., 1977; Morris et al., 1986). A number of authors have already dealt with the problem of the function of intraepithelial lymphocytes in various tissues and organs, such as the tonsil (Koburg, 1967), epidermis (Andrew and Andrew, 1949), lung (Bienenstock et al., 1973), and gut (Andrew and Sosa, 1947). Most have concluded that intraepithelial lymphocytes are concerned with antigen detection, immunological enhancement, and memory and effector responses through antigens absorbed in the epithelium from the lumen. However, the origins of the intraepithelial lymphocytes and their migratory routes have not yet been made clear. We have already reported that lymphatics and high endothelial venules (HEV) play an important role in the migratory routes in gut‐ and bonchus‐associated lymphoid tissue (GALT and BALT) (Ito et al., 1987; Otsuki and Magari, 1988). In the fallopian tube, little is known of the fine distribution and function of lymphatics.In the present work, the ultrastructure of the lymphoid tissue of the human fallopian tube and the fine distribution and ultrastructure of lymphatics in the fallopian tube were examined using electron microscopy immunohistochemically.