Anti-calreticulin antibodies in patients with inflammatory bowel disease

Although the pathogenesis of inflammatory bowel disease (IBD) is unclear, autoimmune processes seem to play roles in IBD because several types of autoantibodies have been found in it. Calreticulin (CRT) is a soluble Ca2+ binding protein which is present in a wide variety of cells. CRT is localized mainly in the endoplasmic reticulum and is often a target for autoantibodies. The aim of this study was to evaluate the clinical significance of anti-CRT antibodies measured by enzyme-linked immunosorbent assay (ELISA) using the sera of patients with ulcerative colitis (UC) and Crohn's disease (CD).

We measured the serum anti-CRT antibodies of 31 Japanese patients with UC and 24 with CD by ELISA. The controls were 105 subjects: 30 healthy persons, 44 patients with primary biliary cirrhosis (PBC), 21 with systemic lupus erythematosus (SLE) and 10 with acute colitis (AC).

The mean titer of anti-CRT antibodies was significantly higher in patients with UC than in healthy individuals (p <0.05). The prevalence of anti-CRT antibodies in these patients was significantly higher during the initial phase than during the passing phase (p <0.05). In patients with CD, the mean titer of anti-CRT antibodies was not significantly higher than in healthy individuals. The positivity for anti-CRT antibodies, however, was about 30% in those patients, which was as high as in patients with UC, SLE and PBC. In patients with AC, anti-CRT antibodies were all negative.

The positivity of anti-CRT antibodies may have a diagnostic value for IBD, especially in the initial phase of UC.