Effects of interleukin-6 blockade on the development of autoimmune thyroiditis in nonobese diabetic mice

We explored the role of interleukin-6 (IL-6) in the development of autoimmune thyroiditis in nonobese diabetic (NOD) mice, an animal model of Hashimoto's thyroiditis, using anti-mouse IL-6 receptor antibody (MR16-1). Thyroiditis was induced by iodide ingestion or mouse thyroglobulin (Tg) immunization. Mice were injected intraperitoneally with saline, control rat IgG, or MR16-1 (2 or 8 mg). Iodide ingestion did not increase serum IL-6 levels and MR16-1 (2 mg) failed to prevent the development of thyroiditis. In contrast, Tg immunization induced a rapid and significant increase in serum IL-6 levels. While MR16-1 (2 mg) had no effect on Tg-induced thyroiditis, the severity, but not incidence, of thyroiditis was reduced in 8 mg MR16-1-treated mice compared with saline-injected mice. However, thyroiditis development in the 8 mg MR16-1-treated mice was indistinguishable from that in the control IgG-treated mice. MR16-1 (8 mg) did not affect serum anti-Tg antibody levels. These results suggest that IL-6 may play only a minor role in the development of autoimmune thyroiditis in NOD mice.