Detection and partial characterization of Crohn's disease tissue specific proteins recognized by Crohn's disease sera

To identify immunoreactive proteins in Crohn's disease (CD) tissue, we examined intestinal tissues from eight patients with CD, seven patients with ulcerative colitis (UC) and four normal colon specimens from patients with colon carcinoma. Tissues were homogenized in 0.05 M Tris-buffered saline containing 2 mM phenyl-methyl-sulphonyl fluoride, and the cell free supernatants were incubated with sera from eight patients with CD, five with UC and five normal volunteers. Immune complexes formed in vitro were precipitated with pansorbin, washed with several detergents and analysed by SDS-polyacrylamide gel electrophoresis. When CD tissue was immunoprecipitated with CD sera, three major proteins of 160,000, 120,000 and 110,000 daltons were detected. Partial enrichment of these proteins were achieved when immune complexes formed in vitro were precipitated with polyethylene glycol followed by protein A-Sepharose 4B chromatography. Affinity gel chromatography and autoradiographic studies with purified serum IgG from CD patients further confirmed the presence of these immunoreactive proteins in CD tissue extracts. When similarly examined, these proteins were absent from UC and control tissue extracts after incubation with CD, UC or control sera. These studies suggest that CD tissue contains several proteins which are specifically recognized by CD patients' sera. Characterization of these immunoreactive proteins may provide an important lead in understanding the pathogenesis of CD.