Fig. 1.
Hypoxia specifically activates FoxP3 transcription. (A) To study hypoxia as an environmental cue of the inflamed microenvironment, CD45RBhigh T-cell–mediated colitis was used as model inflammatory disease. CD3+ T cells (red) infiltrate into areas of hypoxia (green) during colitis (Left, lower magnification; Right, higher magnification of white dashed box). Shown is immunofluorescence on colonic tissue from Rag1-deficient mice that received 5 × 105 CD45RBhigh CD4 T cells 10 wk prior, with tissue sections stained with hypoxyprobe (green) and nuclear counter staining with DAPI (blue). (Scale bar, 100 μm.) (B) qPCR analysis of mRNA expression in primary mouse CD4 T cells cultured in normoxia or hypoxia for 8 h. (C) Time course of FOXP3 (white bars) and PGK1 (black bars) mRNA in Jurkat T cells, measured by qPCR. (D) Flow cytometric analysis of FoxP3 protein in Jurkats exposed to hypoxia for 27 h (red) relative to normoxia (black) and an isotype control (gray). All plots show mean ± SEM, are representative of two to four independent experiments, and include statistical significance calculated by unpaired t test or ANOVA.