Influence of diet on the induction of experimental autoimmune thyroid disease

Immunization of CBA/J mice with thyroglobulin (Tg) emulsified in complete Freund's adjuvant induces experimental thyroiditis (EAT), a well-characterized model of Hashimoto's disease. Recent studies have suggested that dietary factors play a role in the modulation of the immune response and that diet can have a profound effect on the induction of autoimmune diseases. In this study, we examined the influence of diet on autoimmune thyroiditis in mice. EAT was induced in mice fed ad libitum one of the three diets, a standard maintenance chow (Agway H1000), Purina 5020 Breeding Chow, and Purina 5010 Autoclavable (unautoclaved) Diet. Tg-immunized mice fed the Agway 1000 diet were found to be resistant to the development of autoimmune thyroid disease, with only 4 out of 25 mice developing mild thyroiditis. In contrast, 16 out of 25 mice fed the Purina 5010 diet developed moderate to severe thyroiditis. Mice fed the 5020 diet were partly susceptible: 7 out of 25 developed a mild to moderate thyroiditis. Histologic examination of thyroid glands of diseased mice fed the 5010 and 5020 diets showed marked lymphocytic infiltration with destruction of follicles, compared with mice fed the Agway diet, the latter showing only mild infiltration with preservation of thyroid follicles. Titers of antibody to Tg did not differ among the groups, and there was no significant difference in the IgG isotype subclass usage. The results demonstrate that diet can markedly affect the severity of autoimmune disease in the EAT model. In contrast, diet has little effect on the humoral autoimmune response in this system. These results implicate diet as a factor in the severity of cell-mediated autoimmune destruction and suggest that dietary modification could decrease pathology in some forms of autoimmune disease.