Chicken IL-17F (Interleukin-17F) is a pro-inflammatory cytokine belonging to the IL-17 family that contributes to host defense and inflammatory regulation in chickens (Gallus gallus). IL-17F is produced primarily by Th17-like CD4⁺ T cells, γδ T cells, and other innate lymphoid populations in response to microbial infection and immune stimulation. It signals through the IL-17 receptor complex (IL-17RA/IL-17RC-like receptors) to induce expression of pro-inflammatory cytokines, chemokines such as CXCLi1 and CXCLi2 (avian functional homologs of IL-8), and antimicrobial peptides, thereby promoting heterophil recruitment and enhancing mucosal barrier immunity in respiratory and gastrointestinal tissues. In healthy chickens, basal IL-17F expression is generally low but increases during bacterial, viral, and parasitic infections, including Eimeria spp. (coccidiosis), Salmonella spp., and avian influenza virus, as well as following vaccination or immune challenge. IL-17F often acts in concert with IL-17A to amplify inflammatory signaling and mucosal defense. In poultry immunology research, chicken IL-17F serves as a biomarker of Th17-type immune activation and inflammatory responses, providing insight into host–pathogen interactions, vaccine-induced immunity, and regulation of avian mucosal immunity in commercial and experimental poultry systems.