A trial to assess the amount of insulin antibodies in diabetic patients by surface plasmon resonance.

OBJECTIVE To measure the amount and affinity of insulin antibodies, we performed a trial to establish a new method for quantitative and qualitative analysis of these antibodies by using surface plasmon resonance (BIAcore system). METHODS Real-time detection of insulin antibody interaction and kinetic analysis were performed using the BIAcore system. PATIENTS OR MATERIALS Eight diabetic patients with insulin antibodies and whose fasting total immunoreactive insulin levels were more than 100 microU/ml were selected. The patients with and without recurrent hypoglycemia were classified into hypoglycemic episode-positive or hypoglycemic episode-negative groups, respectively. Seven diabetic patients without insulin antibodies were selected as controls. RESULTS In the 8 patients, the concentration of insulin antibodies ranged from 2.91 to 16.3 microg/ml and insulin antibodies were not detected in the control group. The apparent KD (dissociation constant) and kd (the dissociation rate constant) values of the patients were much larger than those seen for the anti-human insulin monoclonal antibody. The KD values were significantly higher in the hypoglycemic episode-positive group than in the hypoglycemic episode-negative group (p<0.05). No significant differences in the concentration, the ka (the association rate constant) and the kd values were noted between the groups. CONCLUSION The data suggests that insulin antibodies of the patients have an apparently lower affinity status in sera as compared with that for the anti-human insulin monoclonal antibody, and dissociate easily from the immune-complex in the sera, especially in cases where there is recurrent hypoglycemia in the patients. Therefore insulin antibody characteristics are one of the causative factors in hypoglycemic episodes.