Contribution of secretory IgA, polymeric IgA and IgA/secretory component-containing circulating immune complexes to the serum hyper-IgA in diabetes mellitus.

The relative contribution of secretory IgA, monomeric and polymeric IgA and IgA/secretory component-containing immune complexes was investigated in sera of diabetic patients. Secretory IgA and immune complexes containing IgA and secretory component seem to participate in the hyper-IgA of patients with Type 2 (non-insulin-dependent) diabetes only, suggesting an altered hepatic clearance via secretory component receptors on hepatocytes. In Type 1 (insulin-dependent) diabetes, the high serum IgA levels might be explained by an increase in IgA production in response to antigenic stimuli. Evidence is also accumulated that immune complexes containing IgA of mucosal origin may be involved in microangiopathy production in Type 2 diabetes.