Methimazole inhibits thyroid autoantibody production by an action on accessory cells.

It is now possible to demonstrate production of thyroglobulin antibodies by Hashimoto lymphocytes when they are cultured with autologous thyroglobulin-primed accessory cells. When accessory cells are primed with antigen in the presence of the antithyroid drug methimazole, antibody production is blocked. This finding suggests that the immunosuppressive action of this group of antithyroid drugs is mediated by an action on antigen handling by accessory cells.