Assessment of autoantibodies to interferon-ω in patients with autoimmune polyendocrine syndrome type 1: using a new immunoprecipitation assay.

BACKGROUND: Measurements of autoantibodies to interferon-ω (IFN-ω) in patients with autoimmune polyglandular syndrome type 1 (APS-1) were performed using a new immunoprecipitation assay (IPA) based on 125I-labeled IFN-ω. METHODS: We have developed and validated a new IPA based on 125I-labeled IFN-ω. Sera from 78 patients (aged 3-78 years) with clinically diagnosed APS-1, 35 first degree relatives, 323 patients with other adrenal or non-adrenal autoimmune diseases and 84 healthy blood donors were used in the study. In addition, clinical features and autoimmune regulator (AIRE) genotype for the APS-1 patients were analyzed. RESULTS: Sixty-six (84.6%) of 78 APS-1 patients were positive for IFN-ω Ab using 125I-labeled IFN-ω IPA. IFN-ω Ab was the most prevalent of the six different autoantibodies tested in this group of APS-1 patients. All 66 IFN-ω Ab-positive APS-1 patients had AIRE mutations and 7 IFN-ω Ab-negative patients had no detectable AIRE mutations, whereas 3 (3.8%) patients were discrepant for IFN-ω Ab positivity and AIRE mutation results. Out of autoimmune controls studied, two patients were positive for IFN-ω Ab. Positivity and levels of IFN-ω Ab in the APS-1 patients studied were similar irrespective of patient's clinical phenotype and AIRE genotype. Furthermore, IFN-ω Ab levels did not change over time (up to 36 years of disease duration) in 8 APS-1 patients studied. CONCLUSIONS: We have developed a novel, highly sensitive and specific assay for measurement of IFN-ω Ab. It provides a simple and convenient method for the assessment of patients with APS-1 and selecting patients suspected of having APS-1 for AIRE gene analysis.