Expression of certain HLA-I types in cleavage-stage embryos

This study examined the expression of human leukocyte antigen (HLA)-G and HLA-I (which includes HLA-A, -B, -C, -E and –F, but is without HLA-G) in the cleavage embryo and its supernatant, and related the results to embryo development including growth rate and grade. In total, 136 day-3 cleavage embryos were used for detection of HLA-G and 24 embryos for HLA-I without HLA-G by immunohistochemistry. The expression of HLA-I was examined by western blot in the lysates of a further 63 day-3 cleavage embryos; soluble HLA-I in the culture supernatant of embryos with detectable HLA-I was also examined by western blot. It was found that 90 of 136 (66.2%) cleavage embryos expressed HLA-G, whereas 23 of 24 (95.8%) embryos expressed HLA-I without HLA-G. HLA-G expression typically showed an even and symmetrical pattern of distribution in each blastomere. HLA-I without HLA-G in cleavage-stage embryos is typically scattered around the blastomere surface. The expression of HLA-G but without HLA-I in cleavage-stage embryos was significantly associated with embryo grade (P < 0.001) and cell number (P = 0.03). In conclusion, HLA-I is expressed on day-3 cleavage embryos, and HLA-G expression on preimplantation embryos is related to embryo development, including embryo growth rate and embryo grade.