AN INTESTINAL SECRETORY PROTEIN IS FOUND IN MOST GLANDS ASSOCIATED WITH THE GASTROINTESTINAL-TRACT - VONEBNERS AND SALIVARY-GLANDS, GALLBLADDER, AND PANCREAS

We have previously shown that monoclonal antibodies (MAb) prepared aga inst the duodenal mucosa of 4-day-old mice disclosed the presence of t wo antigens associated with the formation of intestinal crypts. One of these, MIM-1/39, was found in the apical cytoplasm of undifferentiate d epithelial crypt cells of the duodenum and colon. We report here the immunolocalization of MIM-1/39 in different glands associated with th e gastrointestinal tract, using a polyclonal antibody produced against antigen MIM-1/39. By indirect immunofluorescence on 1-mum thick Lowic ryl K4M sections, MIM-1/39 was detected in secretory granules of serou s cells in lingual (von Ebner's gland), sublingual, submandibular and parotid glands, and in pancreas; it was also found in epithelial cells of the gallbladder and in the secretory granules of chief cells of ga stric glands. Liver, kidney, and Brunner's glands were not immunoreact ive. Immunocytochemistry revealed the presence of antigen MIM-1/39 in small secretory granules of the gallbladder, duodenum, colon, and in t he large secretory granules in serous cells of lingual and parotid gla nds, in pancreas, and in gastric chief cells. In Western blotting, the MIM-1/39 MAb revealed two bands (330 and 350 KD) in adult mouse duode nal mucosa, gallbladder and stomach, whereas only one (330 KD) was dis closed in pancreatic juice. However, two bands (330 and 350 KD) were d etected in pancreatic juice with the polyclonal antibody. The distribu tion of MIM-1/39 was different from that reported for IgA, bound and f ree secretory components, cryptdin, and Tamm-Horsfall protein. Therefo re, MIM-1/39 appears to be a unique protein. Its exact role remains to be elucidated.