No abstract

During treatment of autoimmune hyperthyroidism, besides normalized thyroid metabolism the level of organ-specific autoantibodies often decreases or disappears at all. Two etiological factors are dis¬ cussed of being responsible for this phenomenon. First, thyroid hormone concentration diminished by the treatment causes reduced autoimmune response. Secondly, antithyroid drugs themselves have been considered to influence the immune system in a direct manner. To elucidate this problem, nu¬ merous in vivo and in vitro experiments have been performed.The following in vivo tests (1-4) were applied in different stages of thyroid metabolism and during therapy with carbimazole. Changes in PPD (tuberculin) reactions, in thyroid auto-AB levels, in the proportion of T-lymphocyte subsets and B-cells as well as the estimation of skin graft survival in ho¬ mologous transplanted rats were investigated.As the corresponding in vitro tests (5-8), the influence of carbimazole on lymphocytic behaviour and on thyroid hormones was proved by using the LTT (lymphocyte transformation test), stimulated specifically and by mitogen (PHA). The capacity of lymphocytes (LY) to produce IG was examined under the same conditions. A possible cytolytic effect of the antithyroid drug was investigated by a cytotoxicity test using LY as targets.Results:1. PPD-mediated reaction was not influenced by the present thyroid metabolism stage but by thyrostatic treatment.2. Thyroid auto-AB levels were shown to decrease during therapy in most cases. 3. No changes in the absolute number of various subsets of LY and IG-concentrations were ob¬ served.4. Skin graft survival was prolonged only in rats treated with extremely high doses. 5. Lymphocytes from patients and healthy controls could not be stimulated by T3 or T4 used in vari¬ ous concentrations. The spontaneous LTT stimulation index also did not differ in patients and in controls.6. Carbimazole was able to suppress PHA-induced blast transformation depending on the drug dose applied. 7. Serum of patients being in clinical and hormonal remission was able to prevent the spontaneous lymphocytic reactions when it was added to the culture. 8. These immune suppressing effects were not induced by a diminished absolute number of LY, as demonstrated by cytolytic tests. Obviously, therefore, carbimazole does influence the function of LY.From these results it can be concluded that one of the effects of thyrostatic drugs found in these investigations is based on their capacity to modulate the immune response. The discrepancy of some findings in the experimental tests in comparison to the corresponding in vivo results is probably caused by higher concentrations of carbimazole in the thyroid gland than in the sera of the patients. 97. Ether-extractable thyroid hormone binding inhibitor (THBI) in non-thyroidal illness