Specificity of hemagglutinin of Falcata japonica which reacts with blood group active N-acetyl-D-galactosamine residues.

Saline extract of the seeds of Falcata japonica has been shown to have hemagglutinating activity for saline red cells of group A, Cad positive and Tn. In titration the extract agglutinates more strongly A2 red cells than the extract of Dolichos biflorus. Because the extract of F. japonica has no ability to agglutinate A3 red cells, it could be used to distinguish the subgroups of A in comparison with the agglutinability of human anti-A serum and D. biflorus lectin. F. japonica extract agglutinates much more strongly with papain-treated A red cells, and papain-treated O and B red cells come to be agglutinated with the extract. The agglutination reactions of lectin of F. japonica with untreated A, and papain-treated A and O red cells are inhibited by A secretor saliva and A substances from human and hog gastric linings. N-Acetyl-D-galactosamine is a potent inhibitor of the hemagglutination reaction in monosaccharides tested. It is directed against terminal GalNAc structures either alpha- or beta-linked.