Platelet membrane glycoprotein Ib: genetic polymorphism detected in the intact molecule and in proteolytic fragments.

Genetic polymorphism of platelet membrane glycoprotein (GP) Ib was studied in 128 healthy German blood donors using immunoblotting with monospecific anti-glycocalicin antibodies. Only three GP Ib forms (B,C and D) were detected. In a smaller number of Vietnamese individuals analysed for comparison all four polymorphic GP Ib forms were found. The frequency distribution of GP Ib phenotypes in the German population was similar to that reported for U.S. Americans of Caucasian origin. GP Ib polymorphism was also observed in purified glycocalicin samples of single donors. Using trypsin-cleaved glycocalicin the polymorphic region could be located in the C-terminal carbohydrate-rich glycocalicin fragment (macroglycopeptide).