NOS2 and infection: We found that Mtb infection significantly increased the expression of tnf-α, 2.49/3.01; ifn-γ, 2.45/4.11; il-1β, 2.76/3.43; and nos2, 2.69/5.98 at 21 and 28 days post-infection respectively (differential expression ≥1.5 fold, P<0.05).