Expression of sucrase-isomaltase and dipeptidylpeptidase IV in human small intestine and colon.

One monoclonal antibody (8A9) against the human sucrase-isomaltase complex and one (4H3) against the human dipeptidylpeptidase IV were produced in the rat and used to immunolabel thin frozen sections of human small intestine and colon. Both enzymes were found to be expressed in the poorly differentiated crypt cells of the small intestine as well as in the mature villous cells, and very low levels were found to be expressed in the colon. Homogeneous immunolabeling of the whole colonic epithelium with the monoclonal antibody 4H3 was often observed, whereas labeling with the monoclonal antibody 8A9, if any, was either restricted to a few crypts and plateaus. The two antibodies were used to perform specific immunoprecipitation of the corresponding antigen, the N-terminal sequence of which was determined after sodium dodecyl sulfate-polyacrylamide gel electrophoresis purification and electroblotting, and were compared with those of other species. In secretor blood group A humans, both the sucrase-isomaltase and the dipeptidylpeptidase IV have type 3 blood group A determinants.