IL-21 regulates the intestinal epithelial TJ barrier function by targeting claudin-5. (A) The effect of IL-21 on intestinal epithelial barrier function. n=3. (B) RT-PCR was employed to detect the mRNA level of claudin-1, claudin-4, claudin-5, claudin-8, claudin-11, occludin, and ZO-1. n=7. (C) The effect of claudin-5 on TEER in Caco-2 cells. n=3. (D) The FD4 level was detected after claudin-5/vector transfection in IL-21 treated cells. n=5. (E, F) The protein level of claudin-5 in different groups. n=4. (G) Representative images of immunofluorescence staining with claudin-5. *P < 0.05, **P < 0.01.