Hematoxylin and eosin-stained light micrographs of histological sections from mice lungs (Magnifications: X10).

<p>Lungs from nonimmunized mice (<b>A</b>), from saline immunized mice (<b>B</b>) and from intranasal OmpA immunized mice (<b>C</b>) showing normal airspaces, interstitium, and bronchioles. <b>D</b>: Intranasal OmpA immunized mouse lung tissue, 24 h after intranasal challenge with a lethal dose of <i>S. flexneri</i> 2a (1×10⁷ CFU/30 µl) showing mild infiltration of neutrophils and other mononuclear cells. <b>E</b>: Lung from saline immunized mice, 24 h after intranasal challenge with a lethal dose of <i>S. flexneri</i> 2a N.Y-962/92 showing severe pneumonia with vascular congestion, peribronchial and perivascular accumulation of inflammatory cells, including polymorphonuclear neutrophils and mononuclear cells.