Immunoreactivity of human insulin of recombinant DNA origin.

To evaluate possible advantages of human insulin of recombinant DNA origin (HI) in the treatment of diabetic patients, we compared cellular and humoral immunoreactivities of HI and porcine insulin (PI). Anti-insulin IgE bound equal amounts of 125I-HI and 125I-PI. There was no difference between HI- and PI-stimulated lymphocyte transformation indices. The binding of 125I-HI with circulating anti-insulin IgG was lower compared with 125I-PI binding (12.1 +/- 1% versus 15.4 +/- 1.5%, P less than 0.001) in 60 insulin-treated cases. Thirteen sera were selected for high antibody titers and analyzed in detail. In the competitive inhibition assays, a 50% displacement of 125I-PI required a fourfold higher concentration of HI than PI. Although total insulin binding capacities were almost equal, 63 +/- 11 nM/L for PI and 60 +/- 12 nM/L for HI, the high-affinity antibodies had significantly reduced avidity for HI compared with PI. These differences in avidities suggest that HI may be useful in treatment of immune-type insulin resistance.