TNF and dry eye syndrome: KCs are equipped with an array of scavenger receptors, Toll-like receptors, complement receptors and Fc receptors through which they detect, bind and internalize pathogens, accompanied by the production of cytokines and chemokines, such as tumor necrosis factor-α (TNF-α), IL-1β, IL-6, IL-12, and IL-18 (37, 48, 49).