FIG. 8.

Loss of IFN-γ activity was not associated with diminished ability to clear a Pseudomonas bacterial challenge but was associated with a high baseline level of endogenous gram-positive bacterial background. IFN-γ knockout mice (IFN KO) or wild-type controls (WT) were subjected to an intravenous injection of P. aeruginosa (5 × 10⁷ CFU) (Pseudo) and were sacrificed 6 h later. Lungs were collected aseptically and homogenized in sterile saline, and serial dilutions were cultured. (A) The number of Pseudomonas CFU in lung homogenates did not differ between wild-type and IFN-γ knockout mice after an intravenous injection of Pseudomonas. (B) Loss of IFN-γ activity was associated with a high background of endogenous gram-positive coccus growth in lung homogenates from animals with, or without, a Pseudomonas bacterial challenge.