Expression of Ahr is independent of the IFN-γ–IDO1 pathway in the lung after HSCT. (A-D) Lethally irradiated B6 mice received BALB/c T cells (5 × 10⁶) and TCD BM cells (5 × 10⁶). Lungs were harvested at the indicated times. (A-B) Expression of Ahr (A) and Cyp1b1 (B) was measured using real-time polymerase chain reaction (PCR). Expression levels are presented as the fold change relative to the value of 1 of naïve lungs (n = 5 per time point). (C) Immunohistochemical staining of AHR on 7-day IPS lung sections. Representative images (×200) are shown. (D) Immunofluorescence staining of AHR plus EpCAM or CD3 on 7-day IPS lung sections. Blue indicates 4′,6-diamidino-2-phenylindole staining. Arrowheads indicate colocalization. Representative images (×400) are shown. (E-F) Lethally irradiated B6.WT or B6.Ido1^−/− mice received BALB/c.WT (5 × 10⁶) or BALB/c.Ifng^−/− T cells (1 × 10⁶) and BALB/c.WT TCD BM cells (5 × 10⁶). Lungs were harvested on day 7. (E) AHR was detected by western blot analysis. (F) Levels of Cyp1b1 expression were determined by real-time PCR. Expression levels are presented as fold change relative to the value of 1 of recipient lungs of TCD BM cells only. (G) Lung epithelial cells were isolated from B6 mice and stimulated with IL-1β plus tumor necrosis factor α (TNF-α) or IL-4 plus IL-13 in the presence or absence of Bay 11-7082. After 24 hours, Ahr expression was determined by real-time PCR. Results are representative of 3 independent experiments with similar results. Data represent mean ± standard error of the mean. (F-G) One-way analysis of variance was performed. ***P < .001. mRNA, messenger RNA.