Determination of the Number and Distribution of Macrophages, Lymphocytes, and Granulocytes in the Mouse Uterus From Mating Through Implantation

The concentration and distribution of F4‐80 positive cells (macrophages) and common leukocyte antigen (CLA) positive (bone marrow derived) cells were assessed in mouse uterus between days 1 and 8 of pregnancy. High numbers of polymorphonuclear leukocytes and lymphocytes were present on days 1 and 2, but not thereafter. Granulocytes were found both in the endometrium and within the luminal epithelium. The percentage of total cells contributed by macrophages was high on days 1 and 2. That percentage decreased significantly on day 3, then increased again on day 5 and remained high through day 8. Macrophages always were found in myometrial stroma. Macrophages were found throughout the endometrium on days 2 through 8. High numbers of macrophages were observed near epithelia, particularly on days 1,2,4, and 5. Few F4‐80 + or CLA + cells were observed within the developing primary and secondary decidua. The results demonstrate that an inflammation‐like cellular response occurs in the uterus following mating and that macrophages are a major cellular component of the uterus during early pregnancy.