Nature https://doi.org/10.1038/s41586-018-0439-x (2018)

The immunological factors that characterize latent tuberculosis infection (LTBI) remain poorly defined. In Nature, Chien and colleagues identify stage-specific host responses to infection with Mycobacterium tuberculosis. People with LTBI have a higher frequency of CD16+ natural killer (NK) cells and a higher frequency of GZMB+PRF+IFN-γ+TNF+ cells with greater cytotoxic potential among NK cells in the blood than that of uninfected people. Patients with active TB have a lower frequency of NK cells than that of those with LTBI, while successful therapy restores the frequency of NK cells to that in uninfected people. In longitudinal studies, the frequency of NK cells decreases in progressors, remains constant in non-progressors, recovers in those who respond to treatment and remains low in non-responders for a 2-year observation period, indicating that circulating NK cells can be used as an indicator of disease progression.