Reduction of thymic GVHD. (A) Experimental protocol. Nonirradiated BDF1 (Ly5.2) recipients received an intravenous injection of B6 (Ly5.1) spleen cells (2.5 × 10⁷) on day 0. BDF1 recipients that received BDF1 spleen cells (2.5 × 10⁷) were used as BMT controls. HVJ liposomes containing 8 μg human HGF cDNA or a mock vector were injected intramuscularly on days 0 and +7 of GVHD induction. (B) On day 14 after GVHD induction, the thymi harvested from HGF-treated GVHD recipients were clearly larger than those from control-treated GVHD recipients. (C) Cellularity of the thymus on day 14 after GVHD induction. Total thymus cells are shown. (D) Cell surface expression of CD4 and CD8. (E-F) Donor T-cell infiltration into the thymus (E) and spleen (F). Donor-derived T cells were distinguished from host cells by the expression of Ly5.1. □ indicates controls; ▪, control-treated GVHD recipients; and ▦, HGF-treated GVHD recipients. Data represent the mean ± SD from 5 mice. ^*P < .05. ^**P not significant. Representative results from 2 similar experiments are shown.