Fig 6. Lung histopathology caused by PA-pneumonia in vaccinated and naive mice.

(A) Immunization and lung collection schedule for (C). (B) Immunization, challenge and lung collection schedule for (D). (C) Representative photomicrographs of histological sections of lungs obtained from mice after IN (IN) immunization with α-PA vaccine (3×10⁷ CFU) (n = 3), IN plus IM (IN+IM) immunization with α-PA vaccine (3×10⁷ CFU) (n = 3) and saline administration (IN+IM) (n = 3). (C) Arrows show perivascular and periarteriolar foci of inflammatory infiltrate of the mononuclear type in the parenchyma. (D) Representative photomicrographs of histological sections of lungs obtained from mice after IN (IN) immunization with α-PA vaccine (3×10⁷ CFU) (n = 6), IN plus IM (IN+IM) immunization with α-PA vaccine (3×10⁷ CFU) (n = 5), saline administration (IN+IM) (n = 5) and challenge with PA14 (1×10⁶ CFU). (D) Arrows show a severe inflammatory infiltrate of the polymorphonuclear type dispersed throughout the pulmonary parenchyma. Arrowheads show polymorphonuclear infiltrate filling most of the alveoli (saline), areas of scarce inflammatory mononuclear infiltrate (IN-immunized mice) and areas of inflammatory infiltrate of the polymorphonuclear type leukocyte with intrabronchial location (IN+IM-immunized mice), respectively. (C, D) The columns show images with ×25 (left), ×100 (center left), ×200 (center right) and ×400 (right) magnifications.