Partial characterisation of the human erythrocyte antigen Pta

Ghosts were prepared from erythrocytes positive for the rare blood group antigen Pta. Immunoblotting of the solubilised ghosts with anti-Pta located the antigen on a band with an Mr of 31,600, about 1,100 higher than that of sialoglycoprotein gamma. Binding to the same band was also observed when cytoskeleton preparations from Pt(a+) erythrocytes were immunoblotted with the antibody. Haemagglutination and immunoblotting experiments were consistent in demonstrating that the Pta antigen is not inactivated by treatment of intact erythrocytes with neuraminidase or trypsin but is destroyed by treatment with alpha-chymotrypsin, papain or pronase. The data indicate that the Pta antigen is carried on a 'new' erythrocyte membrane protein.