Figure 2.

Proposed scheme of lung iron regulation during infection and inflammation. Bacteria secrete siderophores to capture host iron. The host combats this by increasing import of iron (lactoferrin (Lfn), DMT1), decreasing export of iron through ferroportin (Fpn), and increasing iron stores through ferritin. Secreted Lfn and NGAL bind free iron and siderophore-bound iron in the airway to prevent bacterial iron uptake. Inset shows an alveolar macrophage during infection. Alveolar macrophages phagocytose bacteria as a host defense response. NRAMP1 is expressed in macrophage phagosomes and transports iron out of the phagosome to limit iron availability to pathogens. Solid arrows indicate direction of iron transport.