Levels of insulin binding immunoglobulin G (IgG) were determined by the method of Christiansen in diabetic patients divided into the following groups: 1. recently diagnosed diabetics, treated from the beginning with monocomponent (MC) pork insulin (12 patients); 2. diabetics treated from the beginning with several times reerystallized monospeeies (MS) pork insulin (6 patients), and 3. diabetics previously treated for long periods with commercial insulin and changed to MC pork insulin ( 11 patients). The patients were observed for periods of from several months to two years. In patients treated with MC insulin, levels of insulin antibodies in the serum were not significantly increased, except in 3 patients who had viral hepatitis before or during insulin therapy and in an other patient immediately after an attack of influenza. In a majority of the patients treated with MS insulin, an increase in levels of insulin antibodies in the serum was observed. Patients previously treated with eommercial in-sulin had very high titers of insulin antibodies in their serum, which decreased after changing over to lVIC insulin. In this group, some patients, in spite of continuation of treatment with MC insulin, developed increasing levels of insulin-binding antibodies in the serum during a later period of observation.
The results indicate that during treatment of diabetes with insulin, contaminating pancreatic proteins due to shortcomings in production technology are responsible for immunogenicity of the insulin preparations. However, immunogenic properties of pure insulin may become manifest under clinical conditions in patients whose immune system has been sensitized by different factors.