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 μg 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 < 0.05) for D13 ewes and least (P < 0.05) for E ewes. Numbers of T₆ lymphocytes for these same areas were greatest (P < 0.05) for PHA-treated horns of OVX ewes. Overall, the T₄/T₈ ratio (P < 0.004) and mean number of T₁₉ cells (P < 0.009) were increased by PHA. Numbers of CD45R lymphocytes were not affected by PHA but were greater (P < 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> 0.05) between non-pregnant and pregnant horns; however, the number of CD45R lymphocytes was greater (P < 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.