Effect of cyclosporin A on suppressing develoment of autoimmune thyroiditis resisted by iodine

  Objective   To studyte supression of Cyclosporin Ain the development of experimental autoimmune thyroiditis(EAT)thatresisted by iodine and then tofurther understand the role of iodine in the pathog ensis of autoimmune thyroiditis(AT).

  Methods   EATmodel was established in rats of EATgroup and CsA-treatmentgroup with the differentiodine intake levels by immunization with thyrog lobulin of porcine.The rats of CsA-treatmentgroup were injected with the CsA 5 mg/(kg·d)throug h the abdomen on the day 10 after the firstimmunization.The rats of non-EATcontrol group were notimmunized.Then the pathological changes and infiltration of lymphocyte in thyro id tissue of rats were obser ved.The leel of TGAb, TPO-Ab, T3 and T4 in the serum of rats were detectecd by the method of radioimmuo assay(RIA).

  Results   (1) The thyro id tissues of EATgroup and CsA-treatmentgroup were infiltrated by lymphocy te and the more intake of iodine, the more serious the inflammation in the thyro id tissue was.Butthere was almostno infiltration of lymphocytes in thyroid tissue in the every non-EATcontrol group.Atthe same level of iodine intake, the inflammation of rats in EATgroup was more serious than thatof rats in CsA-treatmentgroup.(2)The level of serum TG-Ab and TPO-Ab in EATgroup and CsA-treatmentgroup was sig nificantly hig her than thatof non-EATcontrol group(P < 0.05).The serum TG-Ab and TPO-Ab of CsA-treatmentgroup was lower thatthatof EATgroup.The level of TG-Ab and TPO-Ab became higher with the increase of iodine intake.(3)The level of T4 was lowerin the rats administered with 100 times iodine intake.There was no statistical significant difference among the groups in T3.

  Conclusion   The increase of iodine intake could obviously aggravate the inflammation reaction of thyroid glands of rats with EATand facilitate the developmentof EAT; CsA could suppress the develo pmentof EATand production of autoantibody to a certain extent.Butthis action could be resisted by iodine excess.The increase of iodine intake enhanced effectof resistance; The high iodine intake could suppress the sy nthesis and release on thyroid hormone.