Comparison of lung lesions in normal and neutropenic mice infected with S pyogenes. Scanning electron micrographs of representative mouse lung tissue sections are shown. Normal (A,C,E) or neutropenic (B,D,F) mice were injected intraperitoneally with (A-B) 5 × 106 CFU S pyogenes, (C-D) 5 × 106 CFU S pyogenes, and 200 μg HKH20 (E-F) 5 × 106 CFU S pyogenes and 50 μg aprotinin. Bar represents 50 μm.