The accumulation of [35S]methimazole by monocytes and macrophages.

We have used an automatic cell harvester and micro culture techniques to examine the accumulation of [35S]methimazole by monocytes, macrophages and lymphocytes. Significant temperature-dependent accumulation of the drug was found in resting monocytes and macrophages; this was increased up to 4-fold by phagocytosis. Lymphocytes accumulated little or no drug and myeloma and leukaemic cell lines accumulated none. These results show that two interrelated cells with endogenous peroxidatic activity take up the antithyroid drug methimazole providing further support for the concept that immunosuppression by this drug in Graves' disease is mediated via an action on antigen-presenting cells.