Macrophages and other endocytic cells in the mouse uterus during the second half of pregnancy and into the postpartum period.

The spatiotemporal distribution of macrophages in the uterine wall of mice in the second half of pregnancy and the early postpartum period has been studied. Macrophages were identified using a combination of morphological criteria, the capacity to endocytose horseradish peroxidase and the expression of the Mac-1 antigen. Macrophages were a consistent feature of the myometrium. Numerous endocytic cells were found in the decidua basalis and metrial gland of pregnant mice and in the 'scar' regions of postpartum mice. However, few of the endocytic cells expressed the Mac-1 antigen. It is concluded that stromal/decidual cells, and not monocyte-derived macrophages, are primarily responsible for the removal of cellular debris in the decidua basalis and metrial gland during the last week of pregnancy and in repair of the uterine wall in the postpartum period.