Treatment with anti–TGF-β MoAb decreased the histological evidence of pneumonitis in infected allogeneic transplant recipients with GVHD. Animals were treated with 100 μg anti–TGF-β or control IgG at days −1, 1, and 3. Mice were infected intranasally at day 0, and histology was performed 4 days after infection. Data represent means ± SE of six individual mice per group, derived from three separate experiments. The difference between anti–TGF-β—treated animals and IgG control–treated animals was significant (P = .0336; Mann-Whitney test).