Preservation of mature donor T-cell expansion and responsiveness to host antigens after BMT. BDF1 recipients received TBI (9 Gy) followed by intravenous injection of TCD B6 bone marrow cells (5 × 10⁶) and B6 spleen cells (2.5 × 10⁷) plus P815 cells (10⁴) on day 0. HVJ liposomes containing 8 μg human HGF cDNA or a mock vector were injected intramuscularly on days 0 and +7 of BMT. BDF1 recipients that received TCD B6 bone marrow cells alone were used as BMT controls. On day 14, CTL activity against host antigens and P815 cells (A-B), proliferation (C), and IL-2 production (D) in response to host antigens, and the number of donor CD4⁺ and CD8⁺ T cells (E) were determined with the use of spleen cells of recipients as described in “Materials and methods.” □ indicates BMT controls; ▪, P815-injected GVHD (control treated); and ▦, P815-injected GVHD (HGF treated). Mean counts per minute were as follows: unstimulated cultures for BMT controls, 966 cpm; P815-injected GVHD (control treated), 1644 cpm; and P815-injected GVHD (HGF treated), 1799 cpm. Data represent the mean ± standard deviation (SD) for 3 mice. ^*P < .05 for BMT control versus P815-injected GVHD (control treated and HGF treated). Data of CTL activity are shown as the mean percentage of lysis at a given E/T ratio for 3 mice. Representative results from 2 similar experiments are shown.