Since the cytokine, IL-6, promotes the development of TH17 cells, the higher level of IL-6 in KC patients suggests that the balance between TH17 and TH1 responses as well as IL-6 production is dysregulated in KC, which resulted in the reinforced feedback that increases the IL-1β and IL-17 production in CD4+ T cells. This evidence concerns the gene IL17A and keratoconus.