Proliferation, survival, and effector function of allogeneic T cells in secondary lymphoid organs are not increased in IDO^−/− mice. (A) 60 × 10⁶ CFSE-labeled Balb/c splenocytes were transferred into lethally irradiated B6 or IDO^−/− recipients. Mice were killed on day 4, and spleen was examined by flow cytometry for CFSE dilution and annexin V positivity. Spleen data shown are representative of 4 mice/group per day. Cells were gated on CD4⁺ or CD8⁺, H-2K^b-negative events. Numbers indicate percentage of annexin V–positive cells. (B) Lethally irradiated B6 or IDO^−/− mice were infused with Balb/c TCD BM and 3 × 10⁶ CD4⁺ and CD8⁺ T cells. Drinking water was supplemented with BrdU at days 15 to 20 after transplantation. Spleen and mesenteric LN were harvested and analyzed by flow cytometry for BrdU incorporation. Data are pooled from 2 identical experiments; n = 3 or 4 mice/group. No significant differences were observed. Cells were gated on CD4⁺ or CD8⁺, H-2K^b–negative events. (C) Lethally irradiated B6 or IDO^−/− mice were infused with Balb/c TCD BM and 4 × 10⁶ CD4⁺ and CD8⁺ T cells. Seven days after transplantation, spleens were harvested and analyzed by flow cytometry for FasL, granzyme B, and IFN-γ expression; n = 4 mice/group. Cells were gated on CD4⁺ or CD8⁺, H-2K^b-negative events (*P < .05).