2004), cytotoxic T-cell-mediated Mycobacteria killing (Sud et al. 2006), TNF-α and anti-inflammatory IL-10 (Cilfone et al. 2013) in host defence. Their contributions identified the macrophage infection rate and T-cell-mediated immunity as the two key elements in determining the trajectory of an infection into one of (i) primary TB, (ii) primary TB with clearance, (iii) latency and (iv) reactivation (Marino and Kirschner 2004). The gene discussed is IL10; the disease is tuberculosis.