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 I 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 CLAP 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.