Leucocyte distribution in the uterus during the preimplantation period of pregnancy and phagocyte recruitment to sites of blastocyst attachment in mice

Abstract

Antibodies to antigen F4/80 were used to identify monocyte-lineage cells in the preimplantation uterus and within and between early implantation sites, in intact pregnancy and using a model of delayed implantation, in mice. Neutrophils were identified by morphology and lymphocytes by immunocytochemistry and morphology. Macrophages and neutrophils were found throughout the endometrium on day 2 of pregnancy but were concentrated under the luminal epithelium. Macrophages were evenly distributed throughout the endometrium on days 3-4. Neutrophils were rarely seen on days 3-4, but lymphocytes were found throughout the endometrium, often in groups associated with glands or the luminal epithelium. Within attachment sites, a group of neutrophils was always seen associated with the luminal epithelium within implantation chambers on day 5 or, in ovariectomized, progestagen-maintained animals, at 20 h after a nidatory dose of 20 ng oestradiol. Macrophages were scarce in the subepithelial region of attachment sites and were absent from decidual tissue. 5C6, a monoclonal antibody that binds to a functional epitope of the type 3 complement receptor (CR3), a leucocyte adhesion integrin, was given before nidatory oestradiol. Treatment with 5C6 failed to modify the neutrophil recruitment to attachment sites and had no effect on the implantation rate in ovariectomized, progestagen-maintained animals given nidatory oestradiol.