Thyroxine-Binding Antibodies Inhibit T Cell Recognition of a Pathogenic Thyroglobulin Epitope

Thyroid hormone-binding (THB) Abs are frequently detected in autoimmune thyroid disorders but it is unknown whether they can exert immunoregulatory effects. We report that a THB mAb recognizing the 5′ iodine atom of the outer phenolic ring of thyroxine (T4) can block T cell recognition of the pathogenic thyroglobulin (Tg) peptide (2549–2560) that contains T4 at aa position 2553 (T4(2553)). Following peptide binding to the MHC groove, the THB mAb inhibited activation of the Ak-restricted, T4(2553)-specific, mouse T cell hybridoma clone 3.47, which does not recognize other T4-containing epitopes or noniodinated peptide analogues. Addition of the same THB mAb to T4(2553)-pulsed splenocytes largely inhibited specific activation of T4(2553)-primed lymph node cells and significantly reduced their capacity to adoptively transfer thyroiditis to naive CBA/J mice. These data demonstrate that some THB Abs can block recognition of iodine-containing Tg epitopes by autoaggressive T cells and support the view that such Abs may influence the development or maintenance of thyroid disease.