Swine Interleukin-15 (IL-15) is a cytokine that plays an important role in regulating innate and adaptive immune responses in pigs (Sus scrofa). IL-15 is produced by a variety of cell types, including monocytes, macrophages, dendritic cells, and epithelial cells, in response to infection or inflammatory stimuli. Swine IL-15 signals through a receptor complex composed of IL-15Rα together with the shared IL-2/15Rβ (CD122) and common γ chain (γc), activating intracellular signaling pathways such as JAK–STAT that promote lymphocyte proliferation, survival, and activation. In pigs, IL-15 is particularly important for the development, maintenance, and activation of natural killer (NK) cells and memory CD8⁺ T cells, supporting cytotoxic immune responses against infected or abnormal cells. It also contributes to regulation of mucosal immunity and inflammatory responses in tissues such as the respiratory and gastrointestinal tracts. In cell culture, recombinant swine IL-15 is commonly used to stimulate proliferation and survival of NK cells and cytotoxic T lymphocytes, maintain memory CD8⁺ T cell populations, and enhance cytotoxic activity in in vitro immune assays. Swine IL-15 is widely studied in veterinary and translational research, including investigations of immune responses to important swine pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV), African swine fever virus (ASFV), and Salmonella spp., where IL-15-mediated activation of cytotoxic lymphocytes helps researchers evaluate vaccine candidates and antiviral immune responses.