The platelet glycoprotein Ia‐IIa‐associated Br‐alloantigen system is expressed by cultured endothelial cells

Summary. To obtain information on the immunological relationship between the endothelial and platelet glycoprotein (GP)Ia‐IIa (VLA‐2) complex, we studied whether endothelial GPIa‐IIa was able to express the platelet GPIa‐IIa‐associated Br‐alloantigen system. Therefore, we tested antisera to both allelic forms of the Br system (Bra and Brb) on platelets (by an assay based on monoclonal antibody‐specific immobilization of platelet antigens, MAIPA) and on cultured umbilical vein endothelial cells (by immunoprecipitation experiments) from the same individual. Endothelial cells from a platelet Br(a + b +), and from a platelet Br(a ‐ b +) individual were studied. Our results indicate that endothelial GPIa‐IIa is indistinguishable from platelet GPIa‐IIa in its ability to express the Bra and Brb alloantigens. The association of Br alloantigens with endothelial GPIa‐IIa was confirmed by the results of an assay based on monoclonal antibody‐specific immobilization of endothelial antigens (MAIEA). These data further illustrate the structural and immunologic similarity of platelet and endothelial cell GPIa‐IIa (VLA‐2). Copyright © 1990, Wiley Blackwell. All rights reserved