TNF-alpha is a cytokine produced by monocytes, macrophages, neutrophils, NK cells, CD4+ T cells and many transformed cells. It can be expressed as a 17 kDa free molecule, or as a 26 kDa membrane protein. TNF-alpha easily forms stable trimers, but also other multimeric complexes. In the immune system, it is an important regulator, which has cytolytic and cytostatic activity against a range of tumor cells, increases fibroblast proliferation and supports neutrophil chemotaxis and phagocytosis.
