The MABTNF-A5 antibody, formerly known as 5N, reacts with human tumor necrosis factor, TNF (aka, TNF-α and TNFSF2). TNF is a multifunctional cytokine involved in a variety of immune and inflammatory responses including hemorrhagic necrosis of tumors, septic shock, fever and autoimmune diseases. TNF can regulate the growth and differentiation of many different cell types. It is produced by different activated cell types including macrophages, T lymphocytes, NK cells, dendritic cells, endothelial cells, peripheral blood leukocytes, osteoblasts, astrocytes, mast cells, Kupffer cells, smooth muscle cells, fibroblasts and certain tumor cells. TNF exists in two biologically active forms, i.e., transmembrane and soluble forms. Upon activation, cells express transmembrane TNF glycoproteins that associate as homotrimeric complexes. After enzymatic cleavage, the extracellular region of membrane TNF sheds as a soluble homotrimer. The biologically active form of TNF has been reported to be a trimer. The immunogen used to generate the MABTNF-A5 hybridoma was purified recombinant human TNF. This is an extraordinarily potent neutralizing antibody that is reportedly also useful for ELISA measurements of human TNF.