Expression of H‐Y Antigen on Preimplantation Mouse Embryos

The expression of H-Y antigen on preimplantation mouse embryos has been studied by complement dependent cytotoxicity. Embryos at the 8-cell stage were exposed to anti-H-Y and complement and then scored for cell death. Overall, half of the treated embryos were killed, retarded, or contained dead cells. Of those embryos which were not affected by anti-H-Y, 92% were female. In control experiments, neither normal serum plus complement nor complement alone had any specific effect on male embryos. It is concluded, therefore, that the H-Y antigen is present on preimplantation mouse embryos.