Determination of platelet antigens and glycoproteins in the human fetus

Abstract

The autosomal recessive transmission of Glanzmann's thrombasthenia (GT) and Bernard-Soulier syndrome (BSS), together with requests of families who already had children with these diseases, prompted us to investigate the feasibility of their antenatal diagnosis. The preliminary step leading to the early detection of GT or BSS was to characterize, in the normal human fetus, the platelet antigens and glycoproteins (GPs) and to define their normal amounts on the membrane surface. Blood samples from 32 fetuses between 18 to 26 weeks of gestation were collected by direct puncture of the umbilical vein using an ultrasound-guided needle. Polyclonal antibodies from human origin directed against PLA1, Leka antigens, and the GPIIb IIIa complex (IgGL), or murine monoclonal antibodies specific for GPIb (AN51, 6D1), GPIIIa (AP-3), or GPIIb IIIa (AP-2) were studied using platelet suspension immunofluorescence tests. The binding of each antibody was quantified using a cytofluorograph (Ortho 50H). PLA1 and Leka antigens were expressed in normal amounts on fetal platelets as early as 16 weeks of intrauterine life. The GPIIb IIIa complex quantified by polyclonal or monoclonal antibodies was in the same range in fetuses (IgGL = 427 +/- 23 AUF, AP-2 = 459.5 +/- 8.5; AP-3 = 536 +/- 14) and in adults (IgGL = 420 +/- 30; AP-2 = 498 +/- 11; AP-3 = 515 +/- 13). The platelet binding of antibodies that recognized GPIb was higher in fetuses (AN51 = 491.5 +/- 14; 6D1 = 479 +/- 15) than in adults (AN51 = 426.5 +/- 9; 6D1 = 449 +/- 8.7). These results suggest that immunological techniques can be applied as early as 18 weeks of gestation for the antenatal diagnosis of GT and BSS.