Alloantigenic composition of the endothelial vitronectin receptor.

Endothelial cells synthesize a heterodimeric adhesion molecule, the vitronectin receptor (VnR), which is similar to the platelet glycoprotein (GP)IIb/IIIa complex. The subunits of the endothelial VnR (VnR alpha and GPIIIa) have been studied for their ability to express alloantigens associated with platelet GPIIb and IIIa. We previously showed that endothelial GPIIIa can express the platelet alloantigen Zwa or PIA1, which is associated with GPIIIa. We studied the relationship between the expression of Zwa on platelets and endothelial cells in neonates (n = 13). Using immunoprecipitation and immunofluorescence techniques, we showed that the Zwa antigen is either expressed or absent from both platelets and endothelial cells of the same individual. This finding indicates that in both cell types the same gene is expressed. We also showed that Zwa-negative endothelial cells express Zwb (PIA2), in analogy to Zwa-negative platelets. Moreover, our results strongly suggest expression on endothelial cells of Yukb, a recently described platelet alloantigen, also located on GPIIIa. However, we could not demonstrate expression on the endothelial VnR alpha subunit of Baka, an alloantigen located on platelet GPIIb. These findings are in agreement with the concept that the endothelial GPIIIa subunit is more closely related to its platelet counterpart than to the endothelial VnR alpha subunit.