Factors affecting the insulin autoantibody ELISA

Area of Science:

• Immunology
• Endocrinology
• Autoimmunity

Background:

• Insulin autoantibodies (IAA) are known in insulin-treated patients and early type I diabetes.
• Sporadic reports suggest IAA presence in other conditions, necessitating further investigation.

Purpose of the Study:

• To determine the incidence of insulin autoantibodies in various endocrine and autoimmune diseases in insulin-naive individuals.
• To investigate the presence of insulin-specific IgG autoantibodies in non-diabetic and non-insulin-treated diabetic populations.

Main Methods:

• Enzyme-linked immunosorbent assay (ELISA) was employed to analyze sera from 529 insulin-naive subjects.
• Competitive inhibition assays were used to specifically identify insulin-binding IgG antibodies, overcoming challenges with direct binding methods.
• Populations studied included healthy controls, newly diagnosed type I diabetes, relatives of diabetics, type II diabetes, Graves' hyperthyroidism, and systemic lupus erythematosus.

Main Results:

• Insulin antibodies were most frequent in insulin-treated diabetics (98%) and pre-treatment type I diabetics (37%).
• Insulin-specific IgG autoantibodies were detected in 2-24% of subjects across all tested groups, including controls and those with other autoimmune/endocrine diseases.
• The prevalence varied slightly based on the statistical cut-off used for antibody detection.

Conclusions:

• Circulating insulin-specific IgG autoantibodies are present at low levels in a subset of individuals across diverse endocrine and autoimmune conditions.
• These findings suggest that insulin autoantibodies may represent a component of the normal immune system's repertoire.
• Further research is warranted to understand the clinical significance and origin of these low-level autoantibodies.