Proper embryo implantation depends on the tolerance of the maternal immune system to the fetus and its foreign paternal antigens. During implantation and early pregnancy, the dominant leukocytes in the uterus are uterine NK cells, expressing killer immunoglobulin-like receptors (KIR). KIRs recognize human leukocyte antigens (HLA-C) on the human trophoblast inherited from the father and mother. The antigenic peptides presented by the HLA are formed via their cleavage by endoplasmic reticulum aminopeptidases ERAP1 and ERAP2. The aim of this study was to assess the association of combined KIR genes and their HLA-C ligands, as well as ERAP1 and ERAP2 polymorphisms with recurrent implantation failure after in vitro fertilization (RIF). We tested 491 couples who underwent in vitro fertilization (IVF) and 322 fertile couples. Genotype CC rs27044 ERAP1 in female with a male’s HLA-C1C1 or HLA-C1C2 protected from RIF (p/pcorr. = 0.005/0.044, OR = 0.343; p/pcorr. = 0.003/0.027, OR = 0.442, respectively). Genotype TT rs30187 ERAP1 in female with a male’s HLA-C1C2 genotype increased the risk of RIF. Summarizing, in the combination of female ERAP1 and an HLA-C partner, the rs30187 C>T and rs27044 C>G polymorphisms play an important role in implantation failure.
Keywords: ERAP; HLA-C; KIR; RIF; in vitro fertilization; polymorphism.