H₂O₂ supplementation restored the impaired cell signaling and chemotaxis in AQP3-deficient T cells. (a–d) CD4⁺ T cells from WT and AQP3^−/− mice were stimulated by 500 ng/ml CXCL12 together with/without exogenous addition of 100 µM H₂O₂. (a) Intracellular H₂O₂ levels for 15 s (SE; n = 4; *, P < 0.01, treated vs. control cells). (b) The amount of phosphorylated Itk (SE; n = 4; *, P < 0.01). (c) Quantification of Cdc42 active form (GTP bound; SE; n = 4; *, P < 0.01). (d) Mean fluorescence intensity (MFI) of phalloidin-FITC in the CD4⁺ cells was analyzed (SE; n = 4; *, P < 0.01). (e) T cells were incubated with 100 µM H₂O₂ for 15 s, washed, and assayed for chemotaxis for 30 min toward 200 ng/ml CXCL12 (SE; n = 5; *, P < 0.01). Experiments were performed in one other experiment with similar results.