Swine IL-17A (Interleukin-17A) is a pro-inflammatory cytokine belonging to the IL-17 family that plays a critical role in host defense and inflammatory responses in pigs (Sus scrofa). IL-17A is produced primarily by Th17 CD4⁺ T cells, as well as by γδ T cells—which are abundant in swine—and other innate lymphoid cell populations in response to microbial infection and immune stimulation. It acts on epithelial, endothelial, and stromal cells to induce expression of pro-inflammatory cytokines (e.g., IL-6, TNF-α), chemokines (such as CXCL8), and antimicrobial peptides, thereby promoting neutrophil recruitment and enhancing mucosal barrier immunity in respiratory and gastrointestinal tissues. In healthy pigs, basal IL-17A expression is generally low, but levels increase during bacterial and fungal infections, enteric disease, respiratory inflammation, and parasitic challenge. IL-17A has been implicated in immune responses to pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus, Actinobacillus pleuropneumoniae, and enteric bacteria. In veterinary and translational research, swine IL-17A serves as an important biomarker of Th17-mediated immune activation and neutrophilic inflammation, providing insight into host–pathogen interactions, vaccine-induced immunity, and inflammatory disease mechanisms in both agricultural and biomedical research contexts.