Chicken IL-22 (Interleukin-22) is a member of the IL-10 cytokine family that plays a key role in mucosal immunity and epithelial barrier protection in chickens (Gallus gallus). IL-22 is produced primarily by activated CD4⁺ T cells, including Th17-like cells, as well as by innate lymphoid cells in response to microbial infection and inflammatory stimulation. It signals through the IL-22 receptor complex (IL-22R1 and IL-10R2), which is expressed mainly on epithelial and stromal cells, activating downstream JAK/STAT pathways—particularly STAT3—to induce antimicrobial peptide production, enhance chemokine expression, promote epithelial cell proliferation, and support tissue repair. In healthy chickens, basal IL-22 expression is generally low but increases during bacterial, viral, and parasitic infections, particularly at mucosal surfaces of the respiratory and gastrointestinal tracts. Chicken IL-22 has been implicated in immune responses to pathogens such as Eimeria spp. (coccidiosis), Salmonella spp., avian influenza virus, and infectious bronchitis virus. In poultry immunology research, IL-22 serves as an important biomarker of mucosal immune activation and epithelial defense and is studied in the context of host–pathogen interactions, gut health, and vaccine-induced protective immunity in commercial and experimental poultry systems.