Evaluation of the presence of circulating immune complexes and their relationship to glomerular IgG deposits in streptozotocin-induced diabetic rats.

Circulating immune complexes (CIC) have been postulated to contribute to the development of secondary complications in diabetes mellitus. In this study, CIC were measured in control rats and both insulin deficient and insulin treated streptozotocin-induced diabetic rats. CIC were more prevalent in both groups of diabetic rats as determined by the fluid and solid phase Clq binding assays. By 42 days after induction of diabetes, 80% of insulin deficient and 50% of insulin treated rats had detectable CIC by either/or both assays. As determined by direct immunofluorescence, there was progressive accumulation of rat IgG in the glomerular mesangium. The presence of CIC paralleled the glomerular deposition of IgG. The relationship of circulating insulin levels to the clearance of CIC and the glomerular deposition of IgG is discussed.