APP exhibited hemagglutinating activity toward mouse red blood cells at 4 μg/ml. The effects of various mono- and disaccharides on the hemagglutinating activity of APP were also examined. Hemagglutination was not inhibited by 0.1 M of d-glucose, d-galactose, d-fucose, N-acetyl-d-glucosamine, N-acetyl-d-galactosamine or lactose.