PD-L1 expression in blood was significantly higher in TB patients at diagnosis compared to both latently infected (p = 0.0001) and uninfected contacts (p<0.0001) (median normalised PD-L1 expression; TB patients = 5 arbitrary units; latently infected = 0.7 arbitrary units and uninfected contacts = 0.7 arbitrary units) (Fig 1B). The gene discussed is CD274; the disease is tuberculosis.