IL17A and viral infectious disease: It is believed that Th1-secreted IFN-γ and TNF-α mainly perform cytotoxic functions, such as resistance to viruses and promoting macrophage activation to induce the inflammatory response; Th2-secreted IL-13 induces B-cell proliferation, and Treg-secreted IL-10 mainly inhibits the excessive immune response, while Th17-secreted IL-17 mainly induces the secretion of multiple proinflammatory cytokines from epithelia and endothelia following viral infection (35).