Homing defects of donor T cells to sites of CMV infection. Blood lymphocytes were harvested from 2 groups of donors: cGvHD⁺ CB6F1 mice that previously received transplants of C57Bl/6 donor cells, and cGvHD⁻ C57BL/6 recipients of syngenic transplants. Both groups of recipients were infected with 2.5 × 10⁴ PFUs MCMV intraperitoneally on day 100 after transplantation, and PBMCs were harvested from the pooled blood of 5 infected mice on day 10 after viral infection as described in “Materials and methods.” Three million PBMCs from mice with or without cGvHD were adoptively transferred to 2 groups of irradiated (11 Gy) C57BL/6 mice that were then infected with 3 × 10³ PFUs MCMV intraperitoneally the next day. Nucleated cells were harvested on days 3 and 10 after infection from the blood and spleen (as described in “Materials and methods”) from the infected secondary recipients. The numbers of donor-derived lymphocytes per gram of liver tissue are shown. Donor-derived T cells and MCMV peptide–specific tetramer-positive CD8⁺ T cells per mL blood or gram liver or spleen were counted by using multicolor FACS analysis. (A) MCMV peptide–specific tetramer-positive CD8⁺ T cells per organ measured from the recipients of lymphocytes harvested from cGvHD⁺ donors (□) and from recipients of lymphocytes harvested from no-GvHD donors (▪) on day 3 after MCMV infection. (B) MCMV peptide–specific tetramer-positive CD8⁺ T cells per organ measured on day 10 after MCMV infection. Values represent an average of data from 4 to 5 mice per group (*P < .05 and **P < .005; Student t test). (C) Schematic diagram for the inhibitory effects of cGvHD on the migration and homing of donor T cells to different lymphoid and nonlymphoid organs. #cGvHD interferes with homing of T-cell progenitors to the thymus. ##cGvHD interferes with homing of donor antiviral T cells from blood to lymphoid organs. ###cGvHD interferes with homing of antigen-specific T cells to target organs infected by CMV (eg, lung and liver).