The upregulation of VEGF promoted by IL-6 and Th17-secreted IL-17, combination of IFN-γ from Th1 cells and IL-2 to enhance antigen presentation, and induction of epithelial cell apoptosis by IFN-γ and granase secreted after natural killer (NK) cell activation are all involved in the mechanisms of keratitis[56, 68]. The gene discussed is IFNG; the disease is keratitis.