TROPOMYOSIN ISOFORMS IN INTESTINAL-MUCOSA - PRODUCTION OF AUTOANTIBODIES TO TROPOMYOSIN ISOFORMS IN ULCERATIVE-COLITIS

Background & Aims: Autoantibodies against tropomyosins (TMs) have been reported in ulcerative colitis (UC). In this study the hTM isoforms ( hTM1-5) present in intestinal epithelial cells and in smooth muscle we re investigated, and the immunoreactivity against hTMs by immunoglobul in G (IgG) produced in vitro by colonic mucosal lymphocytes (LPMCs) fr om patients with UC, Crohn's disease (CD), and controls was examined. Methods: TMs were extracted from colonic and jejunal epithelial cells and smooth muscle, and hTM isoforms were identified using isoform-spec ific monoclonal antibodies by enzyme-linked immunosorbent assay and tr ansblot analysis. The immunoreactivity of IgG produced by colonic LPMC s was analyzed against the recombinant hTM isoforms. Results: The majo r hTM isoforms present in colonic and jejunal epithelial cells are hTM 5 and hTM4, whereas intestinal smooth muscle contains the hTM1-3 isofo rms. The IgG synthesized in vitro by LPMCs from UC (n = 19) recognized hTM5 and hTM1, more significantly (P < 0.04 to < 0.001) when compared with CD (n = 12) and controls (n = 17). However, IgG produced by LPMC s from CD did not show such anti-hTM reactivity. Mucosal anti-hTM IgG mainly belonged to the IgG1 subclass. Conclusions: Intestinal epitheli al cells and smooth muscle have distinct hTM isoforms. Patients with U C, and not CD, show mucosal autoantibody response against hTM isoforms , particularly hTM5 and hTM1.