During Th17 cell development, naïve T cells migrate from the thymus and differentiate into Th17 cells in the draining lymphoid tissue on engagement with activated APCs and exposure to the local inflammatory cytokine milieu. TGF-β, IL-6 and IL-23 expressed by the APCs in the draining lymph node play a critical role in the development of pathogenic Th17 cells. Once generated, the migration of CCR6+ Th17 cells to the ocular surface is facilitated by the attractant chemokine CCL-20 at the ocular surface. In addition, activated Th17 cells produce IFN-γ under the influence of IL-12 and IL-23, and these Th17/1 cells contribute to disease exacerbation. In the chronic stage, effector Th17 cells develop into memory Th17 cells (mTh17), which are generated from both Th17 and Th17/1 subsets and maintained by IL-7 and IL-15. These mTh17 cells mediate the chronic inflammation in DED.