Circulating immune complexes in patients with diabetes mellitus.

Circulating immune complexes (CIC) were detected by the solid phase C1q binding assay in 16% of 103 diabetic patients and by the fluid phase C1q binding assay in 31% of patients as compared to 5% of 58 control subjects for each assay. Plasma glucose determinations revealed that most patients were moderately hyperglycaemic (mean glucose = 264 mg/dl), and thus were not selected for tight metabolic control. All but six patients had elevated levels of plasma insulin, including both the insulin treated and diet treated subgroups. There was no correlation between the presence of CIC detected by either assay and plasma glucose, insulin, or the presence of microangiopathy. Multiple factors must contribute to the increase in CIC in both insulin deficient and insulin resistant diabetics. The role of these various factors remains to be defined.