Sensitization to epithelial antigens in chronic mucosal inflammatory disease. I. Purification, characterization, and immune reactivity of murine epithelial cell-associated components (ECAC)

To explore the autoantigenic potential of mucosal epithelium that is the site of several chronic, progressive, inflammatory and yet idiopathic diseases, epithelial cell-associated components (designated ECAC) have been isolated in aqueous-soluble form from everted, inflated loops of murine small intestine, initially characterized biochemically and immunologically, and then purified to homogeneity and studied for a disease association through quantitating, by microcytotoxicity assay, their reactivity with patient mononuclear cells and sera. Hydroxyapatite chromatography successfully separated ECAC into several series of major and minor components, with each series (designated 1, 2A, 2B, and 2C) having a unique chemical profile in terms of total carbohydrate, protein, and specific sugars (sialic acid, fucose, galactose). Furthermore, components within each series were shown not to behave as simple blood group substances antigenically, to be free of contaminating intestinal proteases (less than 0.25 micrograms chymotrypsin or equivalent per milliliter) and to possess shared as well as unique antigenic determinants (1 through 4), all of which appeared to be organ-specific for intestine. Gel filtration on Sephacryl S-200 gave a four-peak elution profile for ECAC consistent with a m.w. for components of 3000 to 232,000. Preparative polyacrylamide gel electrophoresis did isolate individual constituents of ECAC, four of which (P1, P2, P4, and P5) were homogeneous and that could, by a hemagglutination inhibition technique, be shown to possess unique organ-specific antigenic determinants. ECAC-specific reactivity of peripheral blood mononuclear cells and sera from patients in the active phase of a chronic inflammatory disorder involving mucosal epithelium indicated autosensitization had occurred, with involvement of several purified epithelium-derived macromolecules. This reactivity appeared to be antibody dependent, occurred at relatively low effector to target ratios, and was not simultaneously directed to control antigens, isolated from kidney in a manner analogous to that used for ECAC. ECAC, isolated by these techniques, may be sufficiently purified to allow an evaluation of their role in the initiation and/or progression of chronic autoaggressive processes occurring in mucosa.