Cellular Immune Response against Tropomyosin Isoform 5 in Ulcerative Colitis

We have reported an autoantibody response in ulcerative colitis (UC) against human tropomyosin isoform 5 (hTM5), the predominant colonic epithelial cell hTM isoform. In this report, we determined the number of IFN-gamma-secreting cells (spot-forming cells, SFC) against hTM5 by an enzyme-linked immunospot (ELISPOT) assay. Another cytoskeletal protein, caldesmon, CaD40, was used as a control antigen. Peripheral blood mononuclear cells were separated by a Ficoll density gradient from 28 patients with UC, 13 patients with Crohn's disease (CD), and 9 healthy subjects (HS). The mean (+/-SEM) SFC values against hTM5 in UC, CD, and HS were 48.8 +/- 8.1, 18.6 +/- 4.6, and 20.8 +/- 8.6, respectively. The value in UC was significantly higher than those in CD (P < 0.005) and HS (P < 0.025). SFC values in CD did not differ from those in HS. None of the 50 samples (except 1 UC) reacted to the CaD40 antigen. This study demonstrates, for the first time, a defined colon epithelial cell antigen, hTM5, that is capable of inducing a significant T cell response in UC but not in CD.