Variation in the proportion of granulocytes and lymphocyte subsets in the uterus and other immune organs in accord with the estrous cycle in mice

We examined whether the estrous cycle influences the immune system in the u terus and other immune organs of mice. Leukocytes were isolated from the ut erus, liver, spleen, thymus, bone marrow, and peripheral blood and leukocyt e populations were identified by using mAbs in conjunction with two-colour immunofluorescence tests. In the estrogen secretion phase (including the pr oestrus and oestrus stages), the total number of leukocytes in the uterus i ncreased prominently. In other words, the proliferative endometrium in the uterus contained a large number of leukocytes. At this time, leukocytes in the uterus were comprised of NK cells (35%), extrathymic T cells (25%), mac rophages (25%), and granulocytes (15%). Usually, there were few granulocyte s at the other stages in the uterus. In the progesteron secretion phase (in cluding the metoestrus stage), the number of leukocytes in the uterus decre ased inversely. There were also variations in the number of leukocytes and the proportion of leukocyte populations (including lymphocyte subsets). How ever, the variation patterns between the uterus and other immune organs did not synchronize with each other. These results suggest that the estrous cy cle eventually influences the immune system and that the composition patter n of leukocyte populations in the uterus at the oestrus stage (ie., a peak time of the number of leukocytes) is quite similar to that in the uterus du ring pregnancy, in which NK cells, extrathymic T cells, and granulocytes ar e abundant (i.e., in the decidua).