CHARACTERIZATION AND LOCALIZATION OF THE GOV(A B) ALLOANTIGENS TO THEGLYCOSYLPHOSPHATIDYLINOSITOL-ANCHORED PROTEIN CDWL09 ON HUMAN PLATELETS/

The Gov(a/b) alloantigens are expressed on a 175-kD protein (GP175) on human platelets. Anti-Gov alloantibodies have been implicated in post transfusion purpura and alloimmune neonatal thrombocytopenia. In this report we characterize the immunochemistry of the alloantigens and ide ntify the platelet protein that expresses the Gov epitopes. Approximat ely 50% of GP175 containing the Gov epitope was released from platelet s treated with phosphatidylinositol-specific phospholipase C, indicati ng that at least some of this protein exists as a glycosylphosphatidyl inositol (GPI)-linked isoform. Radioimmunoprecipitation and immunodepl etion studies indicated that the Gov(a/b) alloantigens are expressed o n the GPI-anchored CDw109 protein. The Gov(a/b) epitopes were expresse d on an extracellular, 120-kD soluble fragment (p120) of CDw109 produc ed by calcium-dependent protease cleavage. Anti-Gov immunoprecipitates of chymotryptic digests of p120 contained 70- and 52-kD fragments of CDw109. Deglycosylation of native CDw109 had no effect on recognition by Gov alloantisera; however, the epitopes were destroyed after exposu re to sodium dodecyl sulfate. Gov(a/b) alloantigens were expressed on platelets and PHA-activated T-cells, cultured human umbilical vein end othelial cells, and by many different tumor cell lines, consistent wit h the tissue distribution of CDw109. (C) 1995 by The American Society of Hematology.