Endometrial T-lymphocyte subset infiltration during the ovine estrous cycle and early pregnancy.

T-lymphocytes were quantitated within luminal, stromal and glandular areas of ovine endometrium. In experiment 1, ovariectomized (OVX), estrus (E) and day 13 (D13) ewes (six/group) received 500 micrograms of phytohemagglutinin (PHA) or vehicle in ligated right and left uterine horns, respectively. At 48 h, uteri were removed for the immunohistochemical evaluation of T-lymphocyte subsets. In experiment 2, T-lymphocytes were quantitated within non-pregnant and pregnant uterine horns on day 19. For experiment 1, mean numbers of T4 and T8 lymphocytes within luminal and stromal areas of PHA-treated horns were greatest (P less than 0.05) for D13 ewes and least (P less than 0.05) for E ewes. Numbers of T6 lymphocytes for these same areas were greatest (P less than 0.05) for PHA-treated horns of OVX ewes. Overall, the T4/T8 ratio (P less than 0.004) and mean number of T19 cells (P less than 0.009) were increased by PHA. Numbers of CD45R lymphocytes were not affected by PHA but were greater (P less than 0.05) in glandular and luminal than stromal areas. For experiment 2, mean numbers of endometrial T4, T6, T8 and T19 lymphocytes were similar (P greater than 0.05) between non-pregnant and pregnant horns; however, the number of CD45R lymphocytes was greater (P less than 0.05) in endometrial tissue of pregnant than non-pregnant horns. The data indicate that the in vivo response of specific ovine T-lymphocytes to PHA was generally dependent upon reproductive stage and the presence of conceptus tissue influenced the infiltration of CD45R lymphocytes.