IL17A and infection: Upon infection and wounding, IL-17A and IL-17F are rapidly produced by immune and non-immune cells or later by adaptive Th17 cells, subsequently these two released cytokines can induce the expression of host defense genes, such as cytokines (IL-1β, TNF, IL-6, and GM-CSF), chemokines (CXCL1, CXCL2, and CXCL8) and antibacterial peptides (β-defensin and S100 proteins) in targeting cells (epithelial cells, keratinocytes, endothelial cells, fibroblasts, and muscle cells), which will further activate NFκB, MAPKs and C/EBPs downstream pathways to protect the host from harmful pathogens (17, 18).