Instead, the cell-signaling enzymes iNOS, Arg-1, and IDO were significantly up-regulated in both TB (P = 0.019, P = 0.036, and P = 0.019, respectively) and TB/HIV (P = 0.0072, P = 0.022, and P = 0.0012, respectively) compared with the control group (Figure 4, K–M). The gene discussed is IDO1; the disease is tuberculosis.