SPF and BF mice with antibiotic-induced gut flora depletion do not display signs of severe antibody-mediated acute lung injury on lung tissue histology. Lung histology from indicated mouse groups. Panels Ai-Fi and Aii-Fii represent lung tissue images taken at original magnification ×20 and ×40, respectively (hematoxylin and eosin stain). Representative images of each indicated group are shown. Scale bars represent 100 µM (Ai-Fi) and 50 µM (Aii-Fii). WT, wild type.