Association of some cell surface antigens of lymphoid cells and cell surface differentiation antigens with early rat pregnancy.

Monoclonal antibodies and the immunoperoxidase technique were used to localize some cell surface antigens of rat lymphoid cells and cell surface differentiation antigens on cryostat sections of early rat pregnancies. The W3/13 leucocyte sialoglycoprotein was detected almost constantly on trophoblast. The immunoglobulins were more associated with mother's rather than with embryo-derived tissues. We were unable to detect considerable amounts of class I and class II major histocompatibility complex-derived antigens on trophoblast and adjacent decidual cells. The Ia+ cells of the lymphocyte type were occasionally detected in the sites exhibiting presence of immunoglobulins. The Thy-1 cell surface differentiation antigen was detected on the cells producing Thy-1+ material among decidual cells. Depletion of Thy-1 was followed by the regression of decidualized tissue. The OX-2 antigen, known as minor glycoprotein of rat thymocytes, was detected on trophoblast cells and endothelia of decidual vessels, the latter exhibiting also class I major histocompatibility complex-derived antigens. The non-pregnant uterine tissues, as well as the oviduct epithelium were also investigated. The possible role of some of these antigens in the maintenance of the 'immunologically privileged' stage of trophoblast, and in the control of the rearrangement of maternal tissues surrounding the embryo, is discussed.