Further Evidence that Thyroid Peroxidase and the 'Microsomal Antigen' are the Same Entity

The first hint to the nature of the thyroid microsomal antigen was provided by the observation that TPO was antigenical1y related to the microsomal antigen1. Then TPO was purified by monoclonal antibody (mAb) assisted affinity chromatography and shown to react with autoimmune antibodies (aAb) in serum of patients with autoimmune thyroid diseases 2. Titers of anti-TPO and anti-microsomal aAb in serum were found significantly correlated3 which suggested that TPO effectively was the microsomal antigen. Other groups of investigators confirmed that anti-thyroid aAb reacted with TPO, but proposed that TPO was only a part of a putative microsomal antigen complex 5 - 8. To answer the question whether TPO effectively was the microsomal antigen or only a part of i t we undertook different experiments based on the use of highly purified human TPO and mAb to it 9-11