Reactivity of anti-thyroid antibodies to thyroglobulin tryptic fragments: comparison of autoimmune and non-autoimmune thyroid diseases

Studies concerning the antigenicity of thyroglobulin fragments allow the ch aracterization of the epitopes but do not consider the role of heavier anti genic fragments that could result in vivo from the action of endoproteases. Here we assess the relative importance of the fragments obtained from thyr oglobulin by limited proteolysis with trypsin and compare by immunoblotting their reactivity to serum from patients with autoimmune (Graves' disease a nd Hashimoto's thyroiditis) and non-autoimmune (subacute thyroiditis) disea se. The results showed no difference in frequency of recognition of any pep tide by sera from patients with autoimmune thyroiditis. In contrast, sera f rom patients with subacute thyroiditis reacted more frequently with a pepti de of 80 kDa. These results suggest the presence of antibody subpopulations directed at fragments produced in vivo by enzymatic cleavage of thyroglobu lin. This fragment and antibodies to it may represent markers for subacute thyroiditis.