Independent Involvement of CD8 + CD25 + Cells and Thyroid Autoantibodies in Disease Severity of Hashimoto's Disease

Abstract

Hashimoto's disease (HD) is well known as an autoimmune thyroid disease caused by the destruction of the thyroid follicles, and can be diagnosed in the subclinical stage with thyroid-specific autoantibodies. However, some patients with HD develop hypothyroidism and are treated with thyroxine (severe HD), but most do not throughout their lives (mild HD). To clarify the immunologic differences between these two groups of patients with HD, we examined serum thyroid autoantibodies (antithyroid peroxidase antibodies and antithyroglobulin antibodies), CD4⁺ CD25⁺ cells that contain regulatory T cells and activated helper T cells, and CD8⁺ CD25⁺ cells that are activated cytotoxic T cells. There was no significant difference in CD4⁺ CD25⁺ cells between these HD groups, although the proportion of CD25⁺ cells within CD4⁺ cells increased in both groups as compared to normal controls. The serum titers of the thyroid autoantibodies and the proportion of CD25⁺ cells within CD8⁺ cells were higher in patients with severe HD than in those with mild HD. There was no correlation between these two parameters, and a two-dimensional analysis with these parameters differentiated these two groups of patients with HD more clearly. These results indicate that both thyroid autoantibodies and CD8⁺ CD25⁺ cells are independently involved in the disease severity of HD and CD4⁺ CD25⁺ cells are not related to the severity of HD.