Circulating antibodies in diabetics treated with conventional and purified insulins.

Conventional insulins contain impurities which are immunogenic; these include pancreatic polypeptide (PP), glucagon and somatostatin and intermediates of insulin synthesis co-extracted during purification. Monocomponent (MC) insulins are free of these contaminants. In 49 insulin-treated diabetic patients, antibodies were found to insulin (94%), pro-insulin (68%) and PP (68%). Antibodies to glucagon and somatostatin were not detected. There was a significantly lower mean maximum binding and titre of insulin and PP antibodies and total circulating insulin (i.e. antibody bound and free) in patients receiving MC insulin. In patients treated with MC insulins for longer than 2 years there was a significant fall in the mean maximum binding of insulin and total serum insulin, but no consistent change in diabetes control and daily insulin dose. It seems that except in the special instances of fat atrophy, insulin allergy and certain cases of insulin resistance, there is no need to resort to MC insulin.