Cells bearing granulocyte−macrophage and T lymphocyte antigens in the rat uterus before and during ovum implantation

There is little detailed information on the distribution of granulocytes-macrophages and lymphocytes at the pre- and peri-implantation period of the embryo in the uterus. Using two monoclonal antibodies (MAS-099C and MRC-OX41) we found that cells labelled with antibodies specific to either T lymphocytes and thymocytes or granulocytes-macrophages were present in the endometrium and myometrium before ovum implantation. Both types of labelled cells appeared to migrate from the uterine lumen to the deep endometrium, where their number peaked on day 4. At the early implantation period (days 5 to 7), there was a total lack of labelled cells around the conceptus. Specific changes before ovum implantation in the distribution or activation state of T lymphocytes and granulocyte macrophages may favour early embryo acceptance.