Variable cellular composition of inflammatory infiltrates and novel aspects of pulmonary pathology in growth factor–deficient mice. (A) Cellular inflammatory infiltrate surrounding an intraabdominal abscess in a 73-week-old female G−/− mouse illustrating the scarcity of neutrophils (circled) and the predominance of lymphocytes (solid arrow) and macrophages (hollow arrow). Cultures from this abscess grew both Proteus mirabilis and Enterococcus species. (B) Representative view of the cellular inflammatory infiltrate within a bronchiole in an area of pneumonia in a 71-week-old GM−/− mouse illustrating the predominance of morphologically normal neutrophils. (C) Cellular inflammatory infiltrate surrounding a pulmonary abscess in a 37-week-old female G−/−GM−/− mouse illustrating the scarcity of neutrophils, with the majority of cells being lymphocytes (solid arrow) and macrophages (hollow arrow). (D) Representative field of lung abnormality in a 45-week-old female G−/− animal showing marked hypercellularity of alveolar septae in the absence of pulmonary infection (compare with appearance of normal alveolar septae in GM−/− mice in Fig 3A). (E) Similar appearance of alveolar septae in a 64-week-old male G−/−GM−/− mouse with relatively minor surfactant accumulation (arrows). (All sections are stained with H & E; C is original magnification ×2,040, and all others are ×1,360.)