Studies with purified human thyroid peroxidase and thyroid microsomal autoantibodies

Area of Science:

• Endocrinology
• Immunology
• Biochemistry

Background:

• Autoimmune thyroid disease is characterized by autoantibodies against thyroid components.
• Thyroid microsomal antigen is implicated in eliciting autoantibody production.
• The precise relationship between thyroid peroxidase (TPO) and microsomal antigen requires further investigation.

Purpose of the Study:

• To investigate the relationship between purified human thyroid peroxidase (TPO) and the thyroid microsomal antigen.
• To assess the correlation between serum autoantibody levels and TPO binding.
• To evaluate the functional impact of autoantibodies on TPO enzymatic activity.

Main Methods:

• Isolation and purification of human TPO from thyroid tissue.
• Microsomal hemagglutination assay (MCHA) for autoantibody titers.
• Enzyme-linked immunosorbent assay (ELISA) for TPO antibody binding.
• Immunoblotting with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
• Assay of TPO enzymatic activity (guaiacol assay).

Main Results:

• Serum autoantibodies showed good correlation with MCHA titers when binding to purified TPO (r=0.72).
• Immunoblotting confirmed strong correlation (r=0.80-0.84) between antibody binding to TPO's 93 kDa fragment and MCHA titers.
• Patient sera with high MCHA titers significantly inhibited TPO's guaiacol activity (r=0.47).
• Purified TPO inhibited autoantibody binding to thyroid microsomes in high-titer sera.

Conclusions:

• Thyroid peroxidase (TPO) is a major component of the thyroid microsomal antigen.
• Autoantibodies against TPO are strongly associated with autoimmune thyroid disease activity and severity.
• TPO itself can inhibit the binding of autoantibodies to thyroid microsomes, suggesting a potential therapeutic target.