Aspects of humoral immunity in a prospective study of Type I (insulin-dependent) diabetic subjects treated with insulins of different purity.

In 41 Type 1 (insulin-dependent) diabetic patients, islet cell antibodies, anti-insulin antibodies, and immune complexes measured by two different methods (the C1q solid phase assay and the conglutinin binding test) were studied at diagnosis, and the influence of treatment with insulins of different purity was investigated during the first year of treatment. Twenty subjects were treated with conventional insulins (group 1) while 21 were treated with monocomponent porcine insulins (group 2). The prevalence of islet cell antibodies significantly decreased during the 12-month study period in the 41 patients. From the first month anti-insulin antibodies were always significantly higher in group 1 than in group 2. At diagnosis the prevalence of both types of immune complexes in the 41 patients was higher than in normal subjects. The immune complexes measured by the C1q solid phase method showed a significant and progressive reduction during the follow-up period, whereas the immune complexes assayed by conglutinin showed no significant variation in the same period. The presence of C1q immune complexes was found to correlate with the occurrence of islet cell antibodies both at diagnosis and during the follow-up period. The presence of conglutinin immune complexes, on the other hand, tended to parallel the increase of anti-insulin antibody levels.