Photomicrographs of murine lung from wild-type, Plg–/–, and Plg–/–/fXI–/– mice. Shown are sections of lung from 6-week-old mice at × 40 magnification. Panels A, D, and G are from wild-type mice; B, E, and H from Plg–/–/fXI+/+ mice; and C, F, and I from Plg–/–/fXI–/– mice. (A-C) Hematoxylin and eosin. (D-F) Immunostaining with a polyclonal anti–murine fibrinogen/fibrin antibody. (G-I) Masson trichrome stain for collagen. The fields in panels B, E, and H were chosen to show a typical lung lesion in Plg–/– mice. These lesions are patchy, and most pulmonary architecture appears normal. In contrast, the leukocyte infiltration shown in panels C, F, and I for Plg–/–/fXI–/– is typically diffuse by age 6 weeks. Images were taken with an Olympus BX41 microscope (Olympus, Tokyo, Japan) fitted with a DP70 digital camera, using a 40 ×/1.7 NA UPlanF1 objective and Olympus DP controller software (version 1.2.1.108).