[Thyroid peroxidase]

Thyroid Peroxidase (TPO) is a key enzyme in the synthesis of thyroid hormone and is a major thyroid microsomal antigen corresponding to anti-microsomal autoantibodies in thyroid autoimmune diseases. We studied the autoantigenicity, thyroiditogenicity and gene structure of TPO. In micro-ELISA using human TPO as a target, all sera from patients with anti-microsomal antibodies contained IgG class of antibodies to TPO and some sera had IgM class of antibodies. The competitive inhibition test revealed that TPO is the major thyroid microsomal antigen. Experimental murine thyroiditis was successfully induced by the immunization of porcine TPO. Susceptibility of thyroiditis in each strain was very different from that of thyroiditis induced by thyroglobulin. T-cell line specific for porcine TPO could mediate thyroid lesions. Two kinds of full length cDNAs to human TPO were isolated from cDNA library which was constructed from mRNA purified from thyroid with Graves' disease. The longer one consisted of 3,048 nucleotides and its open-reading-frame was likely to encode 933 amino acids. The shorter one lacked 171 nucleotides at the middle portion of the longer one. The structure-gene for human TPO was located on 2q and consisted of 17 exons. One hundred and seventy-one nucleotides deleted in the shorter cDNA exactly corresponded to the 10th exon.