Circulating Immune Complexes among Diabetic Children

Insulin dependent diabetes mellitus (IDDM) is an autoimmune disease associated with the presence of different types of autoantibodies. The presence of these antibodies and the corresponding antigens in the circulation leads to the formation of circulating immune complexes (CIC). CIC are known to persist in the blood for long periods of time. Such CIC following deposition in the small blood vessels have the potential to lead to microangiopathy with debilitating clinical consequences. The aim of our pilot study was to investigate whether a correlation exists between CIC and the development of microvascular complications in diabetic children. Isolation of a new glycoprotein complement inhibition factor (CIF) from the parasitic plant Cuscuta europea seed, which appears to bind specifically to complement component C3 has provided an unique tool for the measurement of immune complexes by means of ELISA-type techniques (CIF-ELISA). We studied the levels of CIC (IgG, IgM and IgA) in 58 diabetic children (mean age 12.28 +/- 4.04 years, diabetes duration 5.3 +/- 3.7 years), 29 of them had vascular complications (group 1) and the other 29 were without vascular complications (group 2). As controls, we studied sera samples from 21 healthy children (mean age 13.54 +/- 4.03 years). Sera from the diabetic patients showed statistically significant higher levels of CIC IgG (p = 0.03) than sera from the control group. In sera from group 1 values of CIC IgG showed statistically significant higher levels than controls (0.720 +/- 0.31 vs. 0.46 +/- 0.045; p = 0.011) Sera from 59% of the patients were positive for CIC IgG, 36% for CIC IgM and 9% for CIC IgA. Among 26 patients with microalbuminuria, sera from 17/26 (65%) were positive for CIC IgG, 8/26 (31%) for CIC IgM and 2/26 (8%) for CIC IgA. CIC IgG correlated with HbAlc (r = 0.51; p = 0.005) and microalbuminuria (r = 0.42, p = 0.033). CIC IgA correlated with age (r = 0.44, p = 0.03). CIC IgM correlated with the duration of diabetes (r = 0.63, p = 0.02). These findings suggest that elevated levels of CIC IgG are associated with the development of early diabetic nephropathy.