Immunological identification of blood group Pk antigen on normal human erythrocytes and isolation of anti-Pk with different affinity.

Abstract

The P1 and Pk blood group glycolipid antigens have the common terminal disaccharide, Gal(alpha, 1-4)Gal, but previous studies indicated that anti-P1 from P2 individuals does not cross-react with Pk antigen. In this paper, the specificities of anti-P1 and anti-Pk were analyzed carefully by complement fixation and hemagglutination techniques and the following results were obtained: (1) Anti-P1 from P2 serum was not absorbed with the Pk glycolipid (CTH), but this antigen absorbed all anti-P1 and anti-Pk (anti-P1Pk) antibodies from the sera of four p individuals. Most of the anti-P1Pk antibodies were IgG, but the anti-p1 from the P2 individual was IgM. (2) The Pk antigen on normal P2 erythrocytes was not 'cryptic'. It was reactive with p serum from which the anti-P antibodies were removed by absorption with the P glycolipid (globoside). This was not appreciated previously because, in order to make anti-Pk reagents, p sera (anti-P1PPk) were absorbed with P1 cells which contain CTH. (3) The anti-P1Pk antibodies in p sera were separated by partial absorption with P1 erythrocytes and elution from the absorbing cells, into two fractions that differ markedly in their affinity for alpha-methyl-D-galactoside and the oligosaccharides prepared from CTH.