CCR5 and CCR1 mRNA expression is increased after allogeneic SCT and is associated with the influx of donor T cells and macrophages into the bronchoalveolar space. RNA was isolated from the lungs of animals on days 7, 14, 28, and 42 after transplantation, and CCR5 and CCR1 expression was determined by RNase protection assay as described in Figure 1. (A-C) Pulmonary CCR5 and CCR1 mRNA expression were significantly increased after allo-SCT at all time points when compared to syngeneic controls. On days 7, 14, and 28 after transplantation, BALF monocyte/macrophage chimerism was determined by flow cytometry using antibodies to CD45.1 (donor marker, ▪) and CD45.2 (host marker, □) and either forward-side scatter characteristics for pulmonary macrophages (D) or costaining for the F4/80 cell surface marker (data not shown). Data are presented as mean ± SEM; n = 3 to 10 animals per group; ^*P < .05, (▪, allogeneic) versus (□, syngeneic).