Six- to 8-week-old male C57BL/6 mice (Charles River Laboratory, Wilmington, MA) and IL-22 KO mice (UC Davis MMRRC, Davis, CA) were used in accordance with the standards of the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. The research protocol was approved by the Yonsei University College of Medicine. The in vivo mouse experiments were performed at the Institute of Vision Research at the Yonsei University College of Medicine. DED was induced in mice as described previously.6 (link), 7 (link), 39 (link), 40 (link) In brief, mice were exposed to a controlled environment chamber (CEC), which allows the controlled regulation and maintenance of the temperature (21 – 23 °C), relative humidity (< 30 %), and airflow (15 L/min). Clinical signs such as corneal erosions were assessed by corneal fluorescein staining using 1% fluorescein (Sigma-Aldrich, St. Louis, MO) according to the standard National Eye Institute scoring system. One week post DED induction, mice were euthanized and tissues were collected for immunohistochemistry and molecular studies. For in vivo IL-22 blockade experiments, 100 μg/mouse of αIL-22 (AF582, R&D Systems, Minneapolis, MN) or PBS were intravenously injected into WT mouse at 2-hour before placing them into the CEC and then daily for 3 days.