Immunohistological characterization of the decidual leucocytic infiltrate related to endometrial gland epithelium in early human pregnancy.

The leucocytic infiltrate which is associated with maternal endometrial glands in decidual tissue in early human pregnancy has been shown by immunohistology to consist mainly of macrophages and T lymphocytes. Cells expressing HLA-DR were prominent around the glands, and most were also reactive for the Leu-M3 tissue macrophage antigen. In addition, HLA-DR-positive T cells were identified by double immunoenzymatic labelling, situated both immediately adjacent to the gland epithelium and in adjacent aggregates. Some accumulation of HLA-DR-positive cells has also been noted around the glands in non-pregnant endometrium during the mid and late secretory phases, and occasional T6 antigen-bearing cells were also detected. Occasional HLA-DR-positive surface and gland epithelial cells were observed in both pregnant and non-pregnant specimens. These results indicate that, in early human pregnancy, the endometrial glands may be subject to a form of active immune response partially under hormonal control.