Regulation of gene expression by AHR is cell intrinsic in lung epithelial cells. (A) Lethally irradiated B6.WT or B6.Ahr^−/− mice were injected with TCD BM cells plus T cells from BALB/c mice. Lung epithelial cells were isolated on day 9 (n = 5 per group). Cytokine messenger RNA (mRNA) levels were measured by real-time polymerase chain reaction (PCR). (B-D) Lung epithelial cells were isolated from naïve B6.WT or B6.Ahr^−/− mice and stimulated with IFN-γ. (B) Levels of Ido1 and Cyp1b1 expression were measured by real-time PCR. (C-D) Lung epithelial cells were treated with IL-1β after 48-hour stimulation with IFN-γ. (C) Levels of cytokine mRNA were measured using real-time PCR. (D) Cytokine levels in cell culture supernatants were measured using the mouse Flex-Set cytokine bead array. (E-F) Mouse splenic (E) or human peripheral (F) CD4⁺ T cells were preactivated with anti-CD3/CD28 and IL-2 for 48 hours and then reactivated in the presence of combined IL-23, TGF-β, and conditioned media of WT or Ahr^−/− lung epithelial cells (E) or A549 cells treated with or without CH-223191 (F). Lung epithelial cells and A549 cells were cultured as described in panel C. Representative dot plots for IL-17A⁺CD4⁺ T cells and concentrations of culture supernatant are presented. IL-17A in cell culture supernatants was measured using the mouse Flex-Set cytokine bead array. Results are representative of 2 (E-F) or 3 independent experiments with similar results. Data represent mean ± standard error of the mean. Nonparametric Mann-Whitney U test (A), 2-way analysis of variance (B-D), and 2-tailed Student t test (E-F) were performed. *P < .05, **P < .01, ***P < 0.001.