Human 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. 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, proteins that regulate immune signaling, apoptosis, and inflammatory pathways. In humans, 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. TNF-α plays a critical role in immune defense against bacterial, viral, and parasitic infections, but dysregulated TNF signaling is also implicated in chronic inflammatory and autoimmune diseases, including rheumatoid arthritis, inflammatory bowel disease, psoriasis, and ankylosing spondylitis. Because of its central role in inflammatory pathology, TNF-α has become a major therapeutic target, with TNF inhibitors such as infliximab, adalimumab, and etanercept widely used to treat inflammatory disorders. Consequently, human TNF-α is extensively studied in immunology, infectious disease research, and inflammatory disease therapeutics, providing key insights into immune regulation and cytokine-mediated pathology.