Increases of IFN-γ, IL-2, IL-4, IL-5, IL-13 or IL-β1 in SAC (25); TSLP in both PAC and SAC (26); and IL-17, IL-21 and IL-22 in dry eyes (27, 28) have been observed in different studies. Here, IL22 is linked to Keratoconjunctivitis sicca.