P-367 Centromeric motif AA of the KIR: the best subrogate marker that defines Alloimmune Reproductive Failure

Abstract Study question Should the centromeric and telomeric motifs been studied separately and taked them in to account in women with recurrent reproductive failure? Summary answer The results show that when the classic KIR study is performed, there is a 12,5% of AA centromeric KIR patients with reproductive failure unidentified. What is known already During human pregnancy, the decidua is mainly populated by NK lymphocytes that express immunoglobulin-type receptors (KIR) recognizing their HLA-C ligands from trophoblast. The objective of this study was to analyze the association of KIR-HLAC phenotypes in couples with sterility, recurrent pregnancy loss (RPL), recurrent implantation failure (RIF), and fetal death (FD) in comparison with reference population and fertile control. Study design, size, duration It is a retrospective real-life observational study from 2015 to 2019 Participants/materials, setting, methods The frequency of the KIR and HLA-C genes were analyzed in 397 women and their partners with reproductive failure. We compare them with 33 fertile controls and reference Spanish population. KIR and HLA-C genotypes of the patients and controls were determined by Lifecodes Sequence-Specific Oligonucleotides (SSO) Typing KIT (Diagnostica Longwood®) performed at Centro de Transfusiones de la Comunidad de Madrid and those of controls at the Hospital Universitario Clínico San Carlos. Main results and the role of chance Centromeric (Cen) AA was the most frequent KIR genotype in women with unexplained RPL and RIG with respect to reference Spanish population (p = 0.001 and 0.02, respectively). Moreover, cenAA was associated with 1.51-fold risk of RPL and 1.2-fold risk of RIF. On the other hand, BB KIR showed lower risk of any reproductive failure tan non-BB KIR (0.12; p