Donor T cell-derived TNF-α is important for the induction of inflammatory chemokines in the lung and the subsequent recruitment of donor effector cells during IPS. Lethally irradiated B6D2F1 mice underwent transplantation as described in Figure 5 (syngeneic, □; allogeneic wild-type, ▪; allogeneic TNF-α^-/-,, allogeneic TNF-α+/+ BM cells mixed with TNF-α-/-T cells, [hatched bar]). (A) Protein levels of RANTES, MIP-1α, MIG, and MCP-1 were determined in the lung on day 7 and 14 after BMT as described in “Materials and methods.” Data are presented as mean ± SEM; day 7 data are from 1 experiment, day 14 data are from 1 experiment representative of 2; n = 6 per group. (B) Reduced chemokine levels early after transplantation are associated with decreased BALF CD4⁺, CD8+, and F4/80⁺ CD11b+ cell numbers by week 5. ^**P < .01; ^*P < .05, and hatched bar versus ▪.