Antibodies to cathepsin G in Crohn's disease.

Antibodies directed against antigens in human neutrophils have proved to be of great diagnostic value in certain systemic vasculitides. Recent reports have focused the attention on these antigens as targets of antibodies in sera of patients with inflammatory bowel disease. We investigated the sera drawn from 60 patients suffering from biopsy proven Crohn's disease and 15 patients with active ulcerative colitis. Using sensitive enzyme-linked immunosorbent assays with purified antigens and Western blotting the following antibodies could be demonstrated: cathepsin G (cat-G) antibodies IgG 38.3%, IgM 13.3%, IgA 23.3% and antibodies against human leucocyte elastase (HLE) IgG, IgA, IgM 3.3%. Low but significant correlations could be found for cat-G antibodies (IgG) and the van HEES index of activity. 73.9% of the cat-G (IgG) positive patients had colon involvement. In the sera of patients with ulcerative colitis no antibodies to cat-G or HLE were detectable. Only 8.3% of the patients with Crohn's disease had antibodies against proteinase 3 (C-ANCA). Our data indicate that cat-G among other myeloid lysosomal enzymes seems to be an important target antigen of antibodies in sera of patients with Crohn's disease. Cat-G antibodies might be helpful to distinguish Crohn's disease from ulcerative colitis.