Simvastatin impairs humoral and cell-mediated immunity in mice by inhibiting lymphocyte homing, T-cell activation and antigen cross-presentation.

Statins block the activity of HMG-CoA reductase, which catalyses the production of mevalonate, an intermediate in cholesterol biosynthesis, which is also a precursor of isoprenoids. In addition to lowering circulating cholesterol, these drugs display anti-inflammatory and immunomodulatory activities in vitro; however, their effects on the development of adaptive immune responses in vivo, as well as the underlying mechanisms, are as yet largely unknown. Here we investigated the outcome of simvastatin treatment on a number of processes, which together orchestrate adaptive immunity to specific antigen. Simvastatin treatment resulted in a marked reduction of T and B cells in spleen, lymph nodes and peripheral blood in mice. This effect could be ascribed principally to an impairment of lymphocyte homing to secondary lymphoid organs. In addition, simvastatin was found to strongly inhibit T-cell responses to the MHCI restricted hen ovalbumin peptide antigen SIINFEKL and to impair ovalbumin uptake and cross-presentation by MHCI. Simvastatin also suppressed antibody responses to immunization with ovalbumin and delayed-type hypersensitivity to allergens. These activities could be largely accounted for by the simvastatin-dependent inhibition of HMG-CoA reductase. The data provide novel mechanistic insight into the activities of simvastatin in the highly complex context of the immune response.