C3metabolism inulcerative colitis andCroln's disease

SUMMARY Themetabolism ofthethird component ofcomplement (C3) hasbeen investigated infour patients with ulcerative colitis, three patients withCrohn's disease andseven control subjects, using radioiodinated C3prepared fromfresh humanplasma. Boththefractional catabolic rate andsynthesis rate ofC3wereincreased inthepatients withinflammatory bowel disease, although theserumC3levels werenormal orraised. Theresults suggest that complement activation mayplay arole inthepathogenesis ofmucosal inflammation inthese diseases.