IFNG and viral infectious disease: Whereas pretreatment with IFN-γ significantly decreased viral infection in wild type Mφ, it had virtually no inhibitory effect in IRF-1-/- cells (3.3-, 34- and 116-fold inhibition in wild type cells versus 1.3-, 1.6- and 2.9-fold inhibition in IRF-1-/- cells, P<0.05 at 1, 10 and 100 IU/ml) (Fig 4B).