Immunological Identification of Blood Group Pk Antigen on Normal Human Erythrocytes and Isolation of Anti-P^k with Different Affinity

Abstract

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