IL17F and immune system disorder: T-helper 17 (Th-17) cell associated cytokines, namely Interleukin-6 (IL-6), Interleukin-17A (IL-17A), Interleukin-17F (IL-17F) and Interleukin-22 (IL-22) are a subset of CD4+ T helper cells which have been shown to play an important role in maintaining the chronic and relapsing phase of multiple immune diseases including DED and SS (66–68).