The Influence of Iodine on the Immunological Properties of Thyroglobulin and its Immunological Complexes

Abstract

Several papers described different immunological properties of thyroglobulin (Tg) after iodination. The influence of iodine-iodide solution on the immunological properties of hTg and its immunological complexes with autoantibodies (aAbs) were studied. Human Tg coated to polystyrene plates, incubated for 30 min with iodine-iodide solution at concentration from 1 to 200 μM at pH 9.0 lost its ability to bind aAbs. Preincubation with iodine (2 μM). decreased aAbs binding by 50%. Tg epitope inactivation induced by iodine depended on the buffer pH and the presence of carbonate ions. The binding of rabbit Tg-antibodies to iodine pretreated Tg was only slightly changed. Thyroglobulin preincubation with iodine solutions decreased aAbs binding from all tested sera (67) of patients with autoimmune thyroid disease (AITD). Excess of iodide (0.2 M KJ) or equimolar concentration of diiodotyrosine protects the Tg molecule from iodine induced inactivation. Immunological complexes of Tg with aAbs dissociate at low iodine concentrations. The results suggest that a product of iodine disproportionation reaction induces changes in the Tg molecule and Tg-aAb's complexes leading to complex dissociation or epitope inactivation.

Key Words:

• Thyroglobulin
• autoantibodies
• epitopes
• iodine