Humoral immune system activity in inflammatory bowel disease.

In vivo activation of complement components C3 and GBG as revealed by crossed immunoelectrophoresis reflects humoral immune system activity in disease. These methods have been applied to a material of 25 patients with ulcerative colitis (UC) and 29 patients with Crohn's disease (CD). Signs of activity in the complement sequence were observed in approximately half the patients of both categories. Fifty blood samples from 30 healthy controls were all negative. The presence of complement activation was correlated with disease activity in both groups, and in patients with CD this could also be shown in longitudinal studies in single patients. In UC complement activation was correlated with the extent of the disease process. The serum levels of factors C4, GBG, and C3 in the patient groups did not differ significantly from those found in the normals.