RESTRICTIONS IN THE RESPONSE TO AUTOLOGOUS THYROGLOBULIN IN THE HUMAN

Abstract

Fragments of thyroglobulin containing the autoreactive epitopes were prepared by an existing procedure, plus an ion-exchange chromatography step which increased their purity. Before purification, 39% of the fragmented material was bound by rabbit antihuman thyroglobulin, only 8% was bound by autoantibody, thus confirming earlier reports of more limited epitopes for human autoantibodies than heterologous antibody. Thyroglobulin autoantibodies in the globulin fractions from 6 human sera showed between 70 and 100% cross-reaction with one another, indicating that the majority of antibodies are directed against the same epitopes. The data are consistent with an estimate of 2 distinct major epitopic specificities with occasional sera having antibodies directed against a 3rd site. Chemical modification of tyrosine residues by iodination did not inhibit the binding of thyroglobulin to human autoantibodies or rabbit anti-human thyroglobulin; tyrosine residues do not contribute significantly to the epitopes for auto- or heteroantibodies.