Tumor necrosis factor (TNF) is a pivotal cytokine that plays essential roles in inflammation, immune regulation, and cell death. Initially discovered for its ability to induce tumor regression, TNF has since been recognized for its complex involvement in various physiological and pathological processes.
Structure and Family
TNF is part of a larger superfamily that includes 19 ligands and 29 receptors. TNFα is a 157-amino-acid protein synthesized as a membrane-bound precursor that is cleaved to release the soluble form. Its receptors, primarily TNFR1 and TNFR2, mediate its biological effects through various signaling pathways, including the activation of nuclear factor kappa B (NF-κB) and c-Jun N-terminal kinase (JNK).
Biological Functions
TNF is involved in numerous physiological processes, including:
- Inflammation: TNF is a key mediator of the inflammatory response, promoting the expression of other pro-inflammatory cytokines and adhesion molecules.
- Cell Survival and Death: TNF can induce apoptosis in certain cell types while promoting survival in others, depending on the context and the signaling pathways activated. This duality is significant in cancer biology, where TNF can either inhibit or promote tumor growth.
- Immune Regulation: TNF plays a crucial role in the activation and differentiation of immune cells, influencing both innate and adaptive immune responses.
