The Metabolism of C3 in Adult Coeliac Disease

Abstract

To study possible pathogenetic mechanisms in adult celiac disease, a metabolic investigation of a component (C3 [3rd component of complement]) of the most important effector of humoral immunity, the complement system, was studied. Purified and biologically active C3 was labeled with 125I and injected together with 131I-labeled albumin into 6 patients with adult celiac disease exhibiting different degrees of disease activity. The same labeled preparations were given to 12 normal individuals. Plasma and urine radioactivity were studied for a total of 8 days. Fractional catabolic rates (FCR) and synthesis rates were calculated by the metabolic clearance method. Other mathematical methods were not used because a final straight exponential was not always obtained, probably owing to extravascular sequestration of protein. An increased FCR was found in most patients, with the highest values seen in active, untreated disease. Activation of complement by immune complexes may be a pathogenetic factor in adult celiac disease.