In vitro Tests of Thyroid Function in Active Thyroglobulin Immunity 1 2

Abstract

Summary

The sensitivity of in vitro thyroid function tests (charcoal ¹²⁵I–T₃ uptake ratio, total serum T₄) in reflecting antibody transport of thyroxine was evaluated in the sera of rabbits with varying amounts of thy-roxine-binding antibodies as facilitated by bleeding rabbits at various intervals after bovine thyroglobulin immunization. Concurrent paper electrophoretic studies of distribution of ₁₂₅I-T₄ in thyroglobulin immune sera were also carried out. In sera with a very low titer of T₄-binding antibodies as revealed by a slight retention of ₁₂₅I-T₄ by gamma globulin in paper electrophoresis, in vitro tests did not provide consistent sensitivity in reflecting such abnormalities in thyroxine transport. In general when paper electrophoretograms of immune sera containing ₁₂₅I-T₄ showed gamma globulin retention of more than 10% of total radioactivity, in vitro thyroid function tests in such immune sera did reflect changes in a direction consistent with that expected in the context of increasing number of T₄-binding sites (as provided by thyroxine-binding antibody molecules). In contrast to the changes in ¹²⁵I-T₃ ratio and total T₄ noted in thyroglobulin-immunized animals, marked changes in these thyroid parameters were not noted in albumin-immunized or adjuvant-treated controls.