(A) TLR 2, TLR 3, and TLR 5 upregulate the expression of IL-17C at mucosal surfaces [see Table 2 for references]. (B) Expression of IL-17C downstream of TNF-α is mediated by ERK1/2, p38, and NF-κB. In the presence of IL-17A, phosphorylation levels of Akt may play a role in synergy between TNF-α and IL-17A stimulation of the expression of IL-17C. IL-17A is also known to increase the expression of MCPIP, which may sequester IL-17C in the cell, preventing release. IL-1β increases IL-17C expression through NF-κB. Co-treatment with IL-13 reduces IL-1β-mediated IL-17C expression via STAT6. Solid arrows represent activation pathways, whereas dashed arrows represent translocation through the nuclear membrane. Images created using BioRender.com