Demonstration of H-2 antigens on preimplantation mouse embryos using conventional antisera and monoclonal antibody.

Mouse embryos at the 2-cell, 8-cell, and blastocyst stages of development were examined for the presence of H-2 antigens by immunoperoxidase labeling and transmission electron microscopy. Conventional antisera made in congenic mouse strains were used to study embryos of four different haplotypes: b, a, k, and d. Blastocysts showed uniform heavy labeling of all cells of the trophectoderm, 8-cell embryos showed lighter labeling of only some of the cells, and 2-cell embryos showed no labeling. Similar results were found for all four haplotypes studied. In addition, monoclonal antibody 11-4.1 (anti-Kk) was reacted with homologous (H-2k) and heterologous (H-2b) blastocysts. Positive results with the monoclonal antibody corroborates the concept that H-2 antigens are expressed on early mouse embryos.