IFNG and infection: For example, it is known that classic activation of macrophages (M1 macrophages) e.g., by gamma interferon together with microbial molecules acting as Toll-like receptor ligands modulates a different program of iron handling as compared to the alternative activation (M2 macrophages) induced by cytokines such as interleukin (IL)-4 and IL-13 induced in certain types of infection or by cues from tissues in steady-state conditions (Recalcati et al., 2012).