Identification of sialosylparagloboside as the erythrocyte receptor for an 'anti-p' antibody.

A human antibody which preferentially agglutinates p erythrocytes is inhibited specifically by the glycolipid sialosylparagloboside, NeuNAc (alpha,2 leads to 3)Gal(beta,1 leads t0 4)GlcNAc(beta,1 leads to 3)Gal(beta,1 leads to 4)Glc-Cer and forms a precipitin band with this compound in agarose gel. Erythrocytes treated with neuraminidase are no longer agglutinated by this antibody, but the agglutination is not affected by papain treatment. Sialosylparagloboside is not a biosynthetic precursor of any of the P antigens, but it contains the lacto-N-neotetraose structure which is also present in the P1 glycolipid.