Complements in diabetes mellitus: activation of complement system evidenced by C3d elevation in IDDM

To characterize insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) in terms of the complement system, some components of the system as well as the related substances and indices were studied. CH50, C3, C4 and C3bINA significantly increased in both IDDM and NIDDM compared with non-diabetic healthy controls. ACH50 was also elevated in NIDDM, whereas it was similar in IDDM and controls. Besides, the serum concentration of C3d, a breakdown product of C3, was higher in IDDM than in NIDDM and healthy controls, but that in NIDDM did not differ significantly from the control. B1Hg1 was not different among IDDM, NIDDM and non-diabetic controls. These observations suggested that there is a high level of complements in both types of diabetes mellitus, but the complement activation seems to be much enhanced in IDDM compared with NIDDM.