PP13, Maternal ABO Blood Groups and the Risk Assessment of Pregnancy Complications

TLDR

Placental Protein 13 (PP13) is a galectin biomarker of preeclampsia that binds ABO blood‑group antigens, potentially altering its blood bioavailability and that of other lectins. The study examined how maternal ABO blood group influences PP13 binding to erythrocytes, serum PP13 levels, and the test’s predictive value for preeclampsia and intrauterine growth restriction. Researchers analyzed PP13 serum data from Caucasian and Hispanic women, performed in vivo, in vitro, and in silico binding assays—including placental immunostainings, erythrocyte flow cytometry, and a computational model of the PP13–H antigen complex. PP13 concentrations and erythrocyte binding were lowest in blood group AB and highest in group B, and adjusting PP13 multiples of the median for ABO blood group improved first‑trimester prediction of preeclampsia and IUGR.

Abstract

Placental Protein 13 (PP13), an early biomarker of preeclampsia, is a placenta-specific galectin that binds beta-galactosides, building-blocks of ABO blood-group antigens, possibly affecting its bioavailability in blood.We studied PP13-binding to erythrocytes, maternal blood-group effect on serum PP13 and its performance as a predictor of preeclampsia and intrauterine growth restriction (IUGR). Datasets of maternal serum PP13 in Caucasian (n = 1078) and Hispanic (n = 242) women were analyzed according to blood groups. In vivo, in vitro and in silico PP13-binding to ABO blood-group antigens and erythrocytes were studied by PP13-immunostainings of placental tissue-microarrays, flow-cytometry of erythrocyte-bound PP13, and model-building of PP13--blood-group H antigen complex, respectively. Women with blood group AB had the lowest serum PP13 in the first trimester, while those with blood group B had the highest PP13 throughout pregnancy. In accordance, PP13-binding was the strongest to blood-group AB erythrocytes and weakest to blood-group B erythrocytes. PP13-staining of maternal and fetal erythrocytes was revealed, and a plausible molecular model of PP13 complexed with blood-group H antigen was built. Adjustment of PP13 MoMs to maternal ABO blood group improved the prediction accuracy of first trimester maternal serum PP13 MoMs for preeclampsia and IUGR.ABO blood group can alter PP13-bioavailability in blood, and it may also be a key determinant for other lectins' bioavailability in the circulation. The adjustment of PP13 MoMs to ABO blood group improves the predictive accuracy of this test.