A new Pk phenotype in the P blood group system.

A healthy 22-year-old woman was noted to have erythrocytes of the Pk phenotype: a strong Pk antigen, no detectable P antigen and anti-P antibody in her serum. Her erythrocytes contained four to six times as much Pk glycolipid (globotriaosylceramide or CTH) and approximately half as much P glycolipid (globotetraosylceramide or globoside) as normal red cells. The structures of CTH and globoside were characterized by analysis of permethylated sugars and complement fixation, in addition to chromatographic mobility and sugar composition. Inasmuch as the erythrocytes of two Pk individuals that were analysed previously (Marcus et al., 1976) contained no detectable globoside, these abnormalities appear to represent a new phenotype in the P blood group system.