Maternal killer-cell immunoglobulin-like receptors and paternal human leukocyte antigen ligands in recurrent pregnancy loss cases in Turkey

HLA-G isoforms, HLA-C allotype and their expressions differ between early abortus and placenta in relation to spontaneous abortions

INTRODUCTION

Spontaneous abortion (SAB) affects approximately 10% of clinically recognized pregnancies. Fetal trophobalst invasion and remodeling of maternal spiral arteries is reported to be dependent on crosstalk between HLA-C/HLA-G expressed on extra villous trophoblast (EVTs)and Killer cell Immunoglobin like receptors (KIRs) of decidual NK (dNK). Immune dysfunction in decidua contributes to early miscarriage.

METHODOLOGY

The study used mother neonate paired cord blood and term placenta samples (n = 46), elective abortus (n = 17,gestational age = 10-12 weeks of pregnancy) and SAB abortus (n = 24, gestational age = 12-15 weeks of pregnancy) for HLA-G, KIR2D and HLA-C. In addition, term placenta was collected from women with history of spontaneous pregnancy loss (n = 24) and women with history of live birth (n = 32). SSP-PCR was used for genotyping, RT-PCR for gene expression, copy number variation (CNVs) and HLA-C allotyping and ELISA for protein expression studies.

RESULTS

Membrane bound HLA-G4 isoform proportion was higher 39.28%, p = 0.02) in term placenta. SAB abortus had higher proportion of HLA-G3 (50%),while elective abortus exhibited higher proportion of soluble isoforms (HLA-G5, = 5.9, HLA-G6 = 5.9%, HLA-G7 = 11.8%). Higher inhibitory KIR2DL1 content and copy numbers with lower HLA-C2 in SAB contrasted with higher copy numbers of KIR2DS1(p = 0.001), KIR2DS1+/2DL1+- HLA-C2 combined genotype in healthy placenta. Elevated KIR2D protein levels (p = 0.001), and concurrently, HLA-C levels were upregulated in healthy placenta.

CONCLUSION

Our data supports lower cognate receptor ligand KIR2DS1+/2DL1+ HLA-C2 together with predominance of HLA-G3 isoform in SAB as confounding factors in spontaneous pregnancy loss. HLA-G isoforms and expression differed between first trimester abortus and term placenta suggesting temporal modulation and marks novelty of the study.

Killer-cell immunoglobulin-like receptor/human leukocyte antigen-C combination and 'great obstetrical syndromes' (Review)

Recurrent pregnancy loss (RPL), pre-eclampsia (PE), fetal growth restriction (FGR), and preterm delivery are examples of 'great obstetrical syndromes' (GOS). Placental dysfunction is the most common pathogenesis of GOS. In human pregnancies, the effects of uterine natural killer cells involve angiogenesis, promoting the remodeling of uterine spiral artery, and improving the invasion of trophoblast cells. The uNK cells supply killer immunoglobulin-like receptors (KIRs), which come into contact with human leukocyte antigen-C (HLA-C) ligands expressed by extravillous trophoblast cells (EVTs). Numerous studies have investigated the association between GOS and KIR/HLA-C combination. However, the outcomes have not been conclusive. The present review aimed to reveal the association between GOS and KIR/HLA-C combination to screen out high-risk pregnancies, strengthen the treatment of pregnancy complications, and reduce the frequency of adverse maternal and fetal outcomes. It has been reported that a female with a KIR AA genotype and a neonate with a paternal HLA-C2 molecule is more prone to develop GOS and have a small fetus since less cytokines were secreted by uNK cells. Conversely, the combination of KIR BB haplotype (including the activating KIR2DS1) and HLA-C2 can induce the production of cytokines and increase trophoblast invasion, leading to the birth of a large fetus. KIR/HLA-C combinations may be applicable in selecting third-party gametes or surrogates. Detection of maternal KIR genes and HLA-C molecules from the couple could serve as useful markers for predicting and diagnosing GOS.