Histologic analysis of lung morphology of HA-Tg mice. D4 cells (10 × 10⁶) were injected intravenously with or without anti–LFA-1 antibody. Lungs were harvested at 48 or 72 hours following cell transfer, sectioned, and stained with H&E. The extent of interstitial inflammation is much less in the anti–LFA-1–treated group compared with the untreated group at 48 hours. Lungs harvested from animals receiving untreated D4 cells show more cellular infiltration and a greater and more widespread thickening of the alveolar walls. At 72 hours, significant alveolitis and mononuclear infiltration of the alveolar spaces are evident in the untreated lungs. Original magnification, × 40. Inset, × 100 magnification.