(en) An interaction between iron homeostasis and immunity has been suggested by a number of investigators. The ability of the immune System to respond adequately to external insults may be impaired in diseases when there is excessive iron accumulation in the reticulo-endothelial System cells such as macrophages, by interfering with multiple pathways that play a central rôle in the immune response. Conversely, the immune System may affect local and systemic iron homeostasis in part by the action of immune mediators, such as cytokines and nitric oxide on the expression and activity of some key proteins of iron homeostasis, i.e. IRP-1 and IRP-2