Immunomodulatory effect of methimazole on inbred mice

The effects of antithyroid drug, methimazole (MMI, 1-methyl-2-mercaptoimidazole), on the immune system of inbred mice, C57BL/6, were studied. The proliferative response of splenic lymphocytes to concanavalin A (Con A) and allogeneic stimulator cells was reduced when the mice were provided with 0.1% MMI in tap water ad libitum for two to four weeks. The reduction of proliferative response was correlated with a lower frequency of proliferative spleen cells in the MMI-treated mice. The ability to produce macrophage activating factor of these spleen cells and the levels of hemolytic plaque-forming cells were also reduced. However, the mitogenic response of the splenic lymphocytes to lipopolysaccharide (LPS) was enhanced. In order to investigate whether the impaired cell-mediated and humoral immune systems would increase the susceptibility of the MMI-treated animal to the growth of tumor cells, mice were challenged with a lethal dose of Moloney virus-induced T cell lymphoma of C57BL/6 mice (MBL-2). The time required for 50% of the animals to die was reduced from 15 days for the normal mice to 10 days for the MMI-treated mice.