The effect of the host's iron status on tuberculosis.

Several lines of evidence have suggested that iron is critical for Mycobacterium tuberculosis growth in macrophages. Macrophage iron loading in patients with African iron overload increases the risk of tuberculosis (TB) and may worsen TB outcome. Likewise, macrophage iron loading may contribute to an increased predisposition toward TB in HIV infection. Human genetic disorders or variations may increase the risk of TB or worsen its outcome through macrophage iron loading, including the haptoglobin 2-2 phenotype, NRAMP1 polymorphisms (at least in Africans and Asians), and possibly ferroportin 1 mutations, but not HFE hemochromatosis. Thus, the host's iron status may be an important yet underevaluated factor in TB prevention and therapy and in TB vaccine design.