Lung tissues were harvested from mice at 24 hours after infection and compared with those without infection or after infection and peptide treatment (single or double administration at 0.1 mg/kg, as described above). Afterwards, they were fixed in situ with 4% paraformaldehyde for 10 minutes with the chest cavity open. The right lobe was embedded in paraffin and 5 μm sections were prepared. Sections were stained with hematoxylin and eosin, and histological evaluation was performed to examine bacterial infection-induced pathological severity. The stained lung sections were evaluated in a double-blind fashion under a light microscope, as described previously52, 53.