Swine Tumor Necrosis Factor Alpha (TNF-α) (also known as TNF or cachectin) is a proinflammatory cytokine that plays a central role in innate immune responses, inflammation, and host defense against pathogens in pigs (Sus scrofa). TNF-α is a member of the tumor necrosis factor (TNF) superfamily, which includes related cytokines such as TNF-β (lymphotoxin-α), Fas ligand (FasL), CD40 ligand (CD40L), and TRAIL, molecules that regulate immune signaling, apoptosis, and inflammatory pathways. In pigs, TNF-α is primarily produced by activated macrophages, monocytes, dendritic cells, and T lymphocytes in response to infection, endotoxin exposure, or tissue injury. TNF-α exerts its biological effects by binding to TNF receptors TNFR1 (p55) and TNFR2 (p75), activating intracellular signaling pathways including NF-κB, MAPK, and caspase-mediated pathways, which regulate cytokine production, immune cell activation, apoptosis, and inflammatory responses. In swine health, TNF-α is involved in immune responses to bacterial, viral, and parasitic infections, including porcine reproductive and respiratory syndrome virus (PRRSV), African swine fever virus (ASFV), and bacterial respiratory pathogens, where it contributes to inflammatory defense and activation of innate immunity. However, excessive TNF-α production can contribute to systemic inflammation, fever, and tissue damage during severe infections. Because pigs are widely used as large-animal models for human immunology and infectious disease, swine TNF-α is extensively studied in veterinary immunology, respiratory disease research, and translational biomedical models, providing insights into cytokine regulation and inflammatory responses relevant to both animal health and human disease.