Histologic analysis of lung tissues with PAO1 challenge at 24 hours after bacterial infection. Mouse lung tissues were harvested, fixed and stained for histological evaluation without peptide treatment (B) or with a single (C) and double (D) administration of Esc(1–21)-1c at 0.1 mg/kg in comparison with non-infected and untreated samples. (A) Infected but untreated mice (B) exhibited more inflammation, airway lumen leukocyte accumulation (black arrow).