MICROPARTICLE-ENHANCED NEPHELOMETRIC IMMUNOASSAY OF ANTITHYROID PEROXIDASE AUTOANTIBODIES IN THYROID-DISORDERS

Crude thyroid peroxidase extracted from human thyroid microsomes was c ovalently bound onto polyacrylic and polyfunctional copolymerized micr oparticles. We observed agglutination of the thyroid peroxidase-microp article conjugate with 13 monoclonal antibodies (mAbs) specific for ep itopes on four different antigenic domains of human thyroid peroxidase (TPO; EC 1.11.1.7), after addition of anti-mouse immunoglobulins. We quantified agglutination by measuring with a specially designed nephel ometer the light scattered by the conjugates. This allowed us to devel op a microparticle-enhanced nephelometric immunoassay for human anti-T PO autoantibodies (aAbs) with defined epitopic specificity, based on t he ability of aAbs to inhibit mAb-induced agglutination. Applied to pa tients with autoimmune thyroid diseases, this assay confirmed the poly clonality of anti-TPO aAbs and their preferential reactivity toward ep itopes located on the A and B antigenic domains of the TPO molecule. T he same specificities seem to be present in patients with Hashimoto th yroiditis or Graves disease.