Does analysis of the antigenic specificities of anti-neutrophil cytoplasmic antibodies contribute to their clinical significance in the inflammatory bowel diseases?

Background: The clinical relevance of anti-neutrophil cytoplasmic antibodies (ANCA) in inflammatory bowel diseases is unclear. Definition of their antigenic specificities may improve their diagnostic significance. Methods: We studied the target antigens of ANCA in 96 patients with ulcerative colitis (UC) and 112 patients with Crohn disease (CD) by indirect immunofluorescence, antigen-specific enzyme-linked immunosorbent assays, and immunodetection on Western blot. We related the presence of antibodies of defined specificity to clinical symptoms. Results: By indirect immunofluorescence, ANCA were present in 58% of UC patients and in 21% of CD patients. Major antigens were catalase, alpha-enolase, and lactoferrin. In UC, ANCA titers correlated with disease activity. In CD, both ANCA, by indirect immunofluorescence, and antibodies to lactoferrin were associated with colonic localization of the disease. Neither ANCA, by indirect immunofluorescence, nor antibodies of defined specificity were associated with duration of disease, use of medication, or a history of bowel resection. Conclusions: ANCA are useful as markers for UC and colonic localization in CD. Definition of the antigenic specificities of ANCA in inflammatory bowel disease does not significantly contribute to their clinical significance.