Ultrastructural localization of glycoprotein IIIa (GPIIIa, β3 integrin) on placental syncytiotrophoblast microvilli: implications for platelet alloimmunization during pregnancy

Abstract

The apical surface of the ST is bathed in maternal blood. During the natural regenerative process of human placenta, senescent parts of the ST are shed into maternal blood during pregnancy. This includes both apoptotic ST nuclei and microparticulate ST debris. The presence of GPIIIa on this circulating ST cellular material could be the source of HPA-1a alloantigen causing primary immunization of susceptible primigravidae early enough for anti-HPA-1a to cause fetal thrombocytopenia during a first pregnancy.