Radioassay Determination of Insulin Autoantibodies in NOD Mice: Correlation With Increased Risk of Progression to Overt Diabetes

In an initial cross-sectional study, 29 female and 25 male nondiabetic weaned nonobese diabetic (NOD) mice of various ages (age range 30–300 days, mean 108 ± 10 days) and 11 unweaned NOD pups were evaluated for competitive insulin autoantibodies (CIAAs) with a fluid-phase radioassay. Eleven of 54 (20%) weaned NOD mice had CIAA levels above the range (>39 nU/ml) of 81 control mice. The group of NOD mice that progressed to diabetes had a significantly higher level of CIAAs than NOD mice that did not progress to diabetes (NOD mice progressing to diabetes: CIAA 63 ± 12 nU/ml; NOD mice not progressing to diabetes: CIAA 8 ± 4 nU/ml; P P 39 nU/ml was therefore 17 ( P + , whereas none of the male animals exceeded the normal range at this age (38 ± 13 vs. 5 ± 6 nU/ml, P + mice developed overt diabetes, whereas none of the NOD mice with CIAAs 1 ) NOD mice express CIAAs to insulin before progressing to overt diabetes, 2 ) these antibodies appear after weaning, and 3 ) CIAA analysis can identify animals with increased or decreased risk of progressing to overt diabetes.