Circulating immune complexes in ulcerative colitis.--II. Correlation with serum protein concentrations and complement conversion products.

Several serum proteins were quantified in twenty-two patients with active ulcerative colitis, and the findings were related to disease activity and occurrence of circulating immune complexes (IC). Conversion of C3 was significantly more frequent in the IC-positive group (eight patients) as compared to the IC-negative group (fourteen patients). Factor B was demonstrable in fifteen out of the twenty-two patients and seven out of the eight IC-positive patients had detectable levels of factor B. There was no difference between the IC-positive and the IC-negative group as regards serum concentrations of the complement factors C3, C4 and factor B, or serum orosomucoid, albumin, IgM and IgG. In contrast, the serum IgA levels tended to be reduced in the IC-positive group. C3 and factor B were significantly elevated in four patients with severe disease activity. In addition, C3, factor B and C4 concentrations showed a positive correlation to the serum orosomucoid levels. The serum concentrations of orosomucoid and albumin were inversely correlated to each other.