Antibodies to human albumin epitopes in type 1 (insulin-dependent) diabetes mellitus.

The presence of antibodies to glycosylated albumin was studied by means of a newly developed sandwich enzyme-linked immunosorbent assay in 29 long-standing Type 1 (insulin-dependent) diabetic patients with microvascular complications and in 20 normal subjects. Two types of antibody reactivity were detected. One directed against glucitol-albumin expressing G and M isotypes. The second, predominantly belonging to the IgG class, reacted with an epitope shared by non-glycosylated albumin and the ketoamine adduct of albumin glycosylation. Both types of antibodies, with affinity constant ranging from 10(4) to 10(7) (mol/l)-1 were found in normal and diabetic subjects, but higher titres were significantly more prevalent in the diabetic patients. These antibodies may represent the result of immune tolerance breakdown or, alternatively, be natural antibodies. Although their function remains to be established, their raised prevalence in Type 1 diabetes may be relevant to diabetic microvascular disease.