CLINICAL-EVALUATION OF BIOTIN-BINDING IMMUNOGLOBULIN IN PATIENTS WITHGRAVES-DISEASE

Biotin-binding immunoglobulin (BBI) was recently identified in human s erum and has been suggested to have a significant association with all ergic and autoimmune disorders. Attempts were made to evaluate the cli nical significance of BBI in autoimmune thyroid disorders. Prevalence of BBI was significantly higher in Graves' disease (47%) than in Hashi moto's disease (8%) and healthy controls (10%). The BBI consisted of h eterogeneous subtypes with respect to binding of several immunoglobuli n classes. Sera in Graves' disease showed predominantly IgG-binding BB I, whereas healthy subjects had IgM-binding BBI. Thyroid stimulating h ormone receptor antibody (TRAb) level was significantly higher in the BBI non-detected group than in the detected group. There was no signif icant relationship between BBI prevalence and thyroid hormone concentr ations, anti-thyroglobulin antibody (TGAb) or anti-thyroid microsomal antibody (McAb) titers. In addition, biotin levels in peripheral blood and red blood cells and biotinidase activity did not differ in the BB I detected and non-detected groups. The present results suggest that B BI is associated with autoimmune dysfunction in Graves' disease.