Lung histology. Four hours after the intratracheal instillation of P. aeruginosa PA103 (5 × 107 CFU), the rats were euthanized and their lungs were perfused with 10% buffered formalin phosphate for fixation and were embedded in paraffin. Mounted sections were stained with hematoxylin-eosin and observed in light microscopy. A. The rat received irrelevant control IgG (4 mg/kg) intratracheally one hour after bacterial instillation. B. The rat received Mab166 (4 mg/kg) intratracheally one hour after bacterial instillation. Magnification of objective lens 20× (left figures) and 40× (right figures).