Thyroid antibodies are produced by thyroid-derived lymphocytes

The significance of the characteristic lymphocytic infiltrate in the target organ in organ-specific autoimmune disease is unknown. We have demonstrated the production of thyroglobulin antibodies and immunoglobulins (IgG, IgM and IgA) by thyroid-derived lymphocytes in Graves' disease and Hashimoto's thyroiditis two plaque forming cell (PFC) assays. The thyroid appears to be an important site of thyroglobulin antibody production but the thyroid lymphocytes also contain many IgG PFCs of non-thyroglobulin specificity. Short-term culture and direct thyroglobulin antibody assay on micro-ELISA plates confirmed the results of the PFC assay. Therapies such as carbimazole may therefore be acting on a localized source of autoantibody production.