Comparison of early host responses to infection. Mutation of CRG2 elicits less edema in the lungs of infected mice. Lungs of mice intranasally infected with crg2Δ, crg1Δ, and WT were collected 0.5, 2, 8 and 48 h post-infection, fixed in formalin, processed and H&E stained. Edema was noted in all time points for crg1Δ and WT-infected animals, and in crg2Δ infected animals 2 h post-infection, n = 3. Black arrows indicate thickened alveolar septa, asterisks indicate areas of RBCs, PMNs and/or macrophages.