The nature and distribution of serologically detectable alloantigens on the preimplantation mouse embryo

The nature and distribution of surface alloantigens on preimplantation mouse embryos has been examined by immunofluorescence. Non-H-2 alloantigens were detected at all stages examined, from the 2-cell to the 4 1/2-day blastocyst. Cleaving blastomeres, inner cell mass cells and cells of the primary trophectoderm were all positive. In F1 embryos maternal non-H-2 alloantigens were detectable at all stages, whereas paternal antigens first became evident at the 6- to 8-cell stage. No convincing evidence of the presence of alloantigens associated with the H-2 haplotype was found at any stage or on any cell type, suggesting that if these antigens are present they are in low quantity or are masked.