Relationship of functional and antigenic interleukin 6 to disease activity in inflammatory bowel disease.

BACKGROUND

Intestinal and peripheral blood mononuclear cell interleukin 6 (IL-6) production in inflammatory bowel disease might present an increased quantity of IL-6 into the systemic circulation. The aim of the present study was to examine the relationship of circulatory IL-6 to the clinical and laboratory expression of inflammatory bowel disease in children.

METHODS

Sera were obtained from 26 children with ulcerative colitis, 49 with Crohn's disease, and 29 control patients. Serum functional IL-6 was measured by a bioassay and antigenic IL-6 by enzyme linked immunosorbent assay.

RESULTS

Functional and antigenic serum IL-6 levels were higher in Crohn's disease than in ulcerative colitis or controls (P < 0.0001) and higher in ulcerative colitis than controls (P < 0.04). In Crohn's disease affecting the colon, functional and antigenic serum IL-6 levels were greater than in disease limited to the small bowel (P < 0.002). Increasing disease severity was reflected by increasing antigenic but not functional IL-6 levels in both Crohn's disease (P < 0.001) and ulcerative colitis (P < 0.02). Serum antigenic IL-6 levels were related to acute phase reactants in both diseases (P < 0.001) whereas functional levels were not.

CONCLUSIONS

Our results underscore the importance of using both functional and antigenic methodologies in examining the relationship of circulating cytokines to the clinical manifestations of inflammatory bowel disease.