Occurrence of antithyroxine antibodies in rabbits immunized with iodine-poor human thyroglobulin.

Thyroglobulin (Tg) is a large glycoprotein with polymorphic structure and its heterogeneity has been demonstrated by many investigators. In order to obtain appropriate antibodies against human Tg which appear in the circulation of patients with thyroid carcinoma, a number of rabbits (19) were immunized with poorly iodinated h-Tg (0.05%). During the period of immunization the level of T3 and T4 was followed in sera, as well as the titre of anti-h-Tg antibodies. The production of antibodies against h-Tg was observed in all immunized rabbits (8, 13, 16, and 54 weeks from the first immunization). Titres of anti-h-Tg antibodies in sera at the 16 and 54-week bleeding were very high (Ka = 2.0 X 10(10) M-1). A few immunized rabbits were found to have a very low concentration of serum T4 (determined by RIA-PEG method). Sera from these animals contained antibodies against T4, but not against T3. Their identification and characterization was performed by a radioimmunological method. In summary, our results show that after immunization of rabbits with low-iodinated, i.e. hormone-poor human Tg, antibodies against thyroxine can be produced. However, occurrence of anti-thyroxine antibodies in some immunized rabbits indicates that the immunogenicity of hormone residues in poorly iodinated h-Tg is much lower than in normal iodinated molecule.