In vivo treatment with anti–TGF-β prevents death from LPD. SCID mice were injected with 50 million PBLs as described in “Materials and methods.” Animals received either PBS (•; n = 3), isotype 100 μg control antibody (♦; n = 5), or 100 μg anti–TGF-β (▪; n = 5) every other day for the duration of the experiment. Animals were confirmed to be engrafted by the presence of more than 750 μg/mL human IgG in their sera and were monitored for LPD development. Survival time was determined for each group. When animals died or became moribund, flow cytometry was performed to confirm the development of LPD. As shown, all control animals (PBS or isotype control antibody) died within 70 days, whereas animals treated with anti–TGF-β antibody survived more than 80 days. The differences in survival were highly significant (P = .004 for PBS versus anti–TGF-β and P = .002 for isotype control versus anti–TGF-β).