RANTES deficiency of donor T cells, but not of bone marrow–derived accessory cells, mediates reduced IPS severity after allogeneic SCT. Lethally irradiated B6D2F1 mice received SCT from either syngeneic B6D2F1 (□) or allogeneic B6 wild-type (▪) or RANTES-/- (▦) donors as described in Figure 3. In addition, groups of B6D2F1 animals received wild-type B6 bone marrow and RANTES-/- B6 T cells (white lined bar) or RANTES-/- B6 bone marrow and wild-type B6 T cells (gray lined bar). The severity of IPS was subsequently assessed in animals that received transplants by measuring lung histopathology (A) and BALF cellularity (B) 6 weeks after SCT. Data are presented as mean ± SEM and are from 1 experiment (pathology; n = 4 to 9 per group, ^**P < .01) or from 2 experiments (BAL cellularity; n = 8 to 17 per group, ^*P < .05. (C) Intracellular RANTES expression in T cells isolated from the lungs 2 weeks after SCT. Mean intensity equals 7.5 ± 0.5 (syn) vs 15.4 ± 2.0 (allo) for CD4⁺ cells and mean intensity equals 7.3 ± 0.4 (syn) vs 22.5 ± 3.3 (allo) for CD8⁺ cells. Data presented are from 1 of 2 comparable experiments; solid gray indicates RANTES, thin black line unfilled indicates isotype control; n = 3 per group.