Reduction in uterine intra-epithelial lymphocytes during early gestation in pigs

The numbers of intra-epithelial lymphocytes per 5 mm of uterine epithelium were counted in cyclic (n = 18) and pregnant (n = 18) gilts on days 10, 13, 16 and 19 postestrus. In cyclic animals these cells increased (P less than 0.01) from 26.4 +/- 1.1 per 5 mm at the mid-luteal phase (day 10) to 47.7 +/- 1.5 per 5 mm at proestrus (day 19). Intra-epithelial lymphocytes were significantly (P less than 0.01) fewer at all stages in pregnant females and were reduced from 17.7 +/- 1.5 on day 10 to 6 +/- 1.4 per 5 mm on day 19. The significant reduction in intra-epithelial lymphocytes during the second and third weeks of gestation indicates that the developing pig conceptus can reduce the numbers of potentially damaging cells at the placental interface.