Abstract
To elucidate the hormonal change and alteration in cytokine expression in peripheral blood mononuclear cells (PBMC) during the early stage of autoimmune thyroiditis, we have developed a canine model of this disease, in which normal dogs were immunized with bovine thyroglobulin (Tg) and/or canine thyroid extract. Serum samples were collected weekly, anti-canine Tg antibody was measured by enzyme-linked immunosorbent assay (ELISA) and thyroid stimulating hormone (TSH) and total T4 levels by radioimmunoassay. We also assayed T lymphocyte proliferation in response to Tg, as well as measuring cytokine mRNA by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). All six dogs immunized with bovine Tg had both canine Tg autoantibody and anti-T4 antibody. When the sample from the highest TgAA titre time-point was compared with baseline the expression of mRNA encoding the Th1-type cytokine such as interferon (IFN)-gamma, interleukin (IL)-18 and IL-15 was increased during the development of autoimmune thyroiditis. Expression of the Th2-type cytokine, IL-6 showed minimal change and IL-4 expression was not detected in any of the samples. Expression of the T suppressive cytokine, IL-10 and transforming growth factor (TGF)-beta was increased in the presence of antigen stimulation. These findings suggest that, although autoimmune thyroiditis is an organ-specific autoimmune disease, systemic cytokine mRNA expression is also changed.