Detection of the terminal fluid-phase complement complex, SC5b-9, in the plasma of patients with insulin-dependent (type I) diabetes mellitus. Relation to increased urinary albumin excretion and plasma von Willebrand factor.

An ELISA was used to measure the fluid-phase complement complex in the plasma of 54 patients with insulin-dependent (type I) diabetes mellitus. Sixty-seven per cent of the diabetic patients had increased levels of SC5b-9. In individual diabetic patients, increased SC5b-9 was found to be significantly associated with the occurrence of anti-heparan sulphate cross-reactive anti-ssDNA antibodies and in some cases with circulating immune complexes.

Increased plasma levels of IgA-IgG immune complexes and anti-F(ab')2 antibodies in patients with type 2 (non insulin-dependent) diabetes mellitus and microangiopathy.

C3 fixing IgA immune complexes were found to be elevated in 25% of patients with type 2 (non insulin-dependent) diabetes mellitus as compared to healthy subjects (2%). Immune complexes containing both IgA and IgG were found in 42% of the diabetic population but not in controls. The presence of C3-IgA and/or IgA/IgG immune complexes correlated with the occurrence of antiglobulins antibodies of IgA class in particular with autoantibodies reactive with the Fab2 portion of IgG.

Cross-reactivity of anti-ssDNA antibodies with heparan sulfate in patients with type I diabetes mellitus.

Anti-single-stranded-DNA antibodies cross-reactive with heparan sulfate were detected in serums of patients with type I (insulin-dependent) diabetes mellitus. The results suggested that heparan sulfate, the major glycosaminoglycan constituent of the glomerular basement membrane, may serve as a target antigen in vivo for cross-reactive anti-DNA antibodies. These polyreactive antibodies, directed toward repeating negatively charged units, may neutralize the heparan sulfate-associated polyanionic sites in the glomerulus, leading to an abnormal permeability of anionic plasma proteins.

Detection of anti-phospholipid (cardiolipin, phosphatidylserine) antibodies in the serum of patients with non insulin-dependent (type 2) diabetes mellitus and macroangiopathy. Coexistence of anti-platelet reactivity.

IgA and IgG antibodies against cardiolipin and/or phosphatidylserine were detected in the sera of patients with non insulin-dependent (type 2) diabetes mellitus. The highest prevalence was observed in particular in patients with macrovascular complications (86%). A significant increase of platelet bound IgA and IgG was observed also in patients with sera positive for anti-phospholipid antibodies suggesting the coexistence of reactivity against phospholipid and platelets.