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

Abstract

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.There is increasing evidence that the immunosuppressive action of methimazole (MMI), the active metabolite of the antithyroid drug carbimazole, is important in determining the outcome of Graves' disease (Weetman et al. 1984a). MMI is concen¬ trated by cells in the thyroid (Marchant et al. 1972) and salivary glands (Connell et al. 1983) as well as by polymorphonuclear leucocytes (Lam & Lindsay 1979). The presence of intracellular peroxidase seems to be important in MMI accumulation (Con¬ nell et al. 1983) and lymphocytes, which do not contain peroxidase, do not accumulate MMI (Shewring & Lazarus 1983). We have shown that the immunosuppressive effect of MMI is probably mediated by an action of antigen-presenting cells, such as the monocyte and macrophage, which have a primary role in triggering lymphocyte activation by antigen; in monocytes the drug inhibits oxygen radical generation (Weetman et al. 1983a(Weetman et al. , 1984b. To support these findings, this study was under¬ taken to determine whether monocytes and macro¬ phages accumulate MMI. Materials and MethodsCell sources and preparation Peripheral blood mononuclear cells (PBM) were pre¬ pared from normal subjects by Ficoll-Hypaque density gradient centrifugation. Monocytes were separated from lymphocytes by adherence to plastic or by Percoli density gradient centrifugation. PBM at a concentration of 2 107/ml in culture medium (RPMI 1640 supplemented with 10% foetal calf serum, 4 mM glutamine, 2 mM pyruvate and 40 mg/1 gentamicin), were added in 100 µ aliquots to 96 well flat-bottomed culture plates (Nunclon Delta SI, Nunc, Kamstrup, Denmark). These were incu¬ bated for 90 min at 37°C at 5% C02 in air, then the non-adherent lymphocytes removed. The plates were washed three times with warm medium and the adherent cells which remained used directly for accumulation studies. The cells were greater than 95% pure monocytes as judged by latex bead phagocytosis. Percoli density gradient centrifugation was performed as described else¬ where (Weetman et al. 1983a). This procedure yields greater than 90% pure monocytes and greater than 95% pure lymphocytes. Neutrophils were prepared by mixing 20 ml heparinised blood with 5 ml of 6% Dextran 150 in saline (Fisons, Loughborough, UK) and removing the buffy coat from the tube after allowing the cells to sediment on the bench for 60 min. Neutrop...

Effect of the inhibition of triiodothyronine (T3) production by thiamazole on the T3 and serotonin content of immune cells

“…It was observed also earlier that thiamazole treatment has some immunosuppressive effect (Chabernaud et al, 1996;Lechpammer et al, 2002), increases interleukin 2 level (Wilson et al, 1990), and lymphocyte proliferation (Sharma and Elias, 1987;Hallengren et al, 1980), accumulates in monocytes and macrophages (Weetman et al, 1984) and causes a marked involution of the thymus (Abou- Rabia and Kendall, 1994). Considering the results of the present experiments these effects can be mediated by T 3 , which is present in the immune cells and inclined to change its concentration under the effect of thiamazole.…”

Circulating Monocyte (Macrophage)‐specific Antibodies in Patients With Autoimmune Thyroid Diseases

“…antibodies have been studied in systemic autoimmune diseases (Pruzanski et al, 1978(Pruzanski et al, , 1983Frank el al., 1979;Linker-Israeli et al, l983;Shirakawa et al, 1985), there have been few studies of the immunological abnormalities of monocyte function in autoimmune thyroid diseases. However, it has been clarified that not only lymphocytes but also monocytes play a role in autoimmune thyroid diseases (Weetman et al, 1983;Iwatani et al, 1986), especially in the immunosuppressive action of the methimazole (Weetman et al, 1984a;b). Monocytes also seem to play some role in other organ-specific autoimmune disorders, notably in insulin-dependent diabetes mellitus (Oschilewski et al, 1985).…”