Circulating immunoglobulin Gi antibody in patients withulcerative colitis against thecolonic epithelial protein detected bya novelmonoclonal antibody

Autoimmunity hasbeenimplicated inthe pathogenesis ofulcerative colitis (UC). Severalstudies haveshownamplified immunoglobulin Gi (IgG1)antibody responseinUC; howevertheimmunoreactive antigen(s) isunknown.Tostudy thisantigen(s), mucosalcolonic extract wasprepared bysonication, ultracentrifugationfollowedby ion exchange chromatography in fastproteinliquid chromatography. Thefraction (enriched colonic peptide), thatwasmostreactive to a novelmonoclonalantibody, 7E,2H12 (IgMisotype), wasisolated andusedto examinetheimmunoreactivity against the patients' serumsamples. Two hundred and thirteen codedsamplesfrom 111 patients withUC (symptomatic and untreated (63), symptomatic andtreated (26),remission (22)); 47 withCrohn's disease (CD)(40weresymptomatic and untreated, and30hadcolonic disease); 29 withacutediarrhoea causedbyspecific pathogen(s); 10 withsystemiclupus erythematosus, and 16normalsubjects were examinedagainstthe enriched colonic peptide byIgGsubtype specific enzyme linkedimmunosorbentassays (ELISAs). TotalIgGantibody reactivity wassignificantly (p<0.01) higheronlyin symptomatic anduntreated UC patients compared witheachofthenon-UCgroup, butthesensitivity wasonly500/o. IgG2and IgG3reactivities werenotdifferent among variousgroups.The IgGi antibody reactivity against theenrichedcolonic peptide, however,differentiated UC patients fromCD andeachoftheother non-UCgroups.Seventy ninepercent of thepatients withUC, treatedor untreated, symptomatic orinremission, hadsignificantly (p<0.0001) higherIgGi antibody against theenrichedcolonic peptide when comparedwitheachof theothernon-UCgroups.Only12% of CD serumsamples andnoneoftheother control serum samplesreacted. Using purified serumIgG1and7E12H,2-IgM, by sandwichELISA,we confirmedthat