SEMINAL FLUID AND THE EXPRESSION OF MHC CLASS-I ANTIGENS IN THE PLACENTA OF THE RAT

PROBLEM: To determine whether seminal fluid influences the expression of MHC class I antigens on the surface of basal trophoblast cells in t he placenta of the rat. METHODS: Transfer of DA x DA embryos into a WF (allogeneic) or DA (syngeneic) recipient made pseudopregnant by hormo nal treatment followed by mating with a vasectomized male (seminal flu id) or by mechanical stimulation (no seminal fluid). Antigen expressio n was determined by electron microscopic immunocytochemistry using the appropriate gold-labeled monoclonal antibodies. RESULTS: Seminal flui d did not affect the expression of MHC class I antigens on the surface of the basal trophoblast in either allogeneic or syngeneic matings. C ONCLUSIONS: The suppression of the expression of paternal class I anti gens on the surface of the basal trophoblast cells in allogeneic pregn ancies most likely occurs at the genome level shortly after fertilizat ion.