IFNG and tuberculosis: Since an age-related decrease in the frequency of NK cells that express NKp46, an activating receptor involved in the recognition of TB-infected monocytes and macrophages (Vankayalapati et al., 2002, Vankayalapati et al., 2005), has been reported (Almeida-Oliveira et al., 2011, Hazeldine et al., 2012), along with a reduction in IFN-γ secretion by NK cells from older adults (Krishnaraj and Bhooma, 1996; J. Hazeldine, unpublished observations), then a weakened NK response may contribute to this greater rate of TB reactivation in older adults (Horsburgh et al., 2010).