Autoimmunity in ulcerative colitis: Humoral and cellular immune response by tropomyosin in ulcerative colitis

Abstract

AIM: Autoimmunity has been emphasized in the pathogenesis of ulcerative colitis (UC). We reported that tropomyosin (TM) or TM related protein is a putative autoantigen in UC. In human fibroblast, at least 8 isoforms of TM have been identified with molecular weight range from 30 kD to 40 kD, depending upon the isoforms, and human TM isoforms (hTM5) has been found the main isoform in human intestinal epithelial cells. In this study, hTM5 was used as a putative auto-antigen for the humoral and T cell immune responses in patients with UC, Crohn’s disease (CD) and healthy subjects (HS) as controls.

METHODS: Anti hTM antibody was examined by enzyme linked immunosorbent assay using human sera (UC 59, CD 28, HS 26) against hTM isoforms. The IFN-γ production by peripheral blood T cells following stimulation by recombinant hTM5 was analyzed by ELISPOT assay.

RESULTS: Anti hTM5 antibody (IgG1) was detected in 15/59 (25.4%) patients with UC, 3/28 (10.7%) with CD, and 3/26 (11.5%) of HS. The OD value in UC was significantly higher than in CD and HS groups (P < 0.05; P < 0.01 respectively). Western blot analysis demonstrated immunoreactivity against hTM5 in several UC sera. ELISPOT assay demonstrated that IFN-γ production is significantly higher in UC (7/18, 39.0%), compared with CD (0/8, 0%) and HS (0/7, 0%), (P < 0.05).

CONCLUSION: A significantly higher immune response to hTM5 was present in UC compared to CD and HS. Further studies of the hTM5/peptides may provide immuno-biochemical mechanism of autoimmune process in UC.

Key Words: Colitis, ulcerative; Autoimmunity; Immunity, cellular; Tropomyosin; Cellular immune response; Enzyme-linked immunosorbent assay