Distribution of blood group substances in normal human colon. Use of the unlabeled antibody (PAP) immunoperoxidase technic to identify A and B blood group substances.

A modification of the unlabeled antibody immunoperoxidase technic, using human antisera to identify blood group substances A and B in normal human colon is described. Overall, staining for the blood group substances is strongest in the cecum and proximal colon; there is a progressive reduction of staining for the blood group substances in the distal colon with almost complete loss in the recto-sigmoid area. The blood group substances are present in epithelial cells and in epithelial mucin, the most intense positive staining often being located in the supranuclear, Golgi region of the cells.