Fungal anti-A agglutinins with different affinities for subgroups A1 and A2 red cells

We found two anti-A hemagglutinating lectins in the extracts of the fruiting bodies of two fungi (93-34, 93-138) belonging to the Tricholomataceae family. The extracts reacted with papain-treated human group A red cells but not with O or B cells. Both fungus lectins gave negative results with saline suspensions of human and animal red cells. In agglutination tests against red cells of A subgroups, 93-34 gave similar results to Dolichos biflorus, such as a stronger reaction with A1 than with A2 cells, while 93-138 showed stronger agglutination of A2 than of A1 cells. Using both fungus hemagglutinating lectins with human standard anti-A serum it was possible to distinguish subgroups of A1 and A2. The activity of both lectins was inhibited by A secretor saliva and A substance from human stomach linings. A-decomposing enzyme from Clostridium tertium A destroyed this inhibiting activity of the reaction of lectins with A cells. N-Acetyl-D-galactosamine was the only potent inhibitor of the hemagglutination reaction among the monosaccharides tested. No agglutination was observed with Cad(+) red cells. The results suggested that two lectins have affinity with terminal alpha-linked N-acetylgalactosaminyl residues of polysaccharide side chains.