Peri-partum changes in the intraepithelial lymphocyte population of sheep interplacentomal endometrium

Previous studies have shown that the proportion of gammadeltaTCR+ large granulated lymphocytes (LGLs) increased markedly during pregnancy and declined dramatically by 2 days after parturition in sheep interplacentomal uterine epithelium. In the present study, the distribution, dynamics and fate of these cells, just before, during and immediately after parturition are described.

Interplacentomal tissues were collected at 140 days postcoitus (dpc), 148 dpc, during parturition, 1-2 hr postpartum, 1 day postpartum (dpp) and 3 dpp, and were studied using light and electron microscopy, and immuno histochemistry. Uterine washings were collected at 148 dpc and examined for the presence of LGLs. Semi-thin Araldite sections taken at different stages were used to quantify the intraepithelial LGLs, non-granulated lymphocytes (NGLs) and apoptotic cells, whereas frozen sections were used to quantify CD45R+, CD8+ and gammadeltaTCR+ intraepithelial lymphocytes (IELs).

A dramatic decline in the proportion of IELs in the luminal epithelium during parturition was observed, mainly because of the decline in CD45R+, CD8+ and gammadeltaTCR+ IELs. There was also a significant decline in the number of granules/ LGL at parturition. This was accompanied by the presence of apoptotic cells of which some were LGLs. The proportions of IELs, LGLs and apoptotic cells markedly increased at 3 dpp. LGLs were found both in uterine washings at 148 dpc and in the uterine lumen at 3 dpp. Apoptosis of glandular epithelial cells was also evident at parturition and markedly increased at 1 dpp.

Our results demonstrated that the dramatic decline in the proportion of gammadeltaTCR+ LGLs at parturition was because of de-granulation, apoptosis and migration of these cells into the uterine lumen.