Apoptosis can be regulated by a variety of extracellular signals that either initiate or inhibit the apoptotic process. One of the best examples of extracellular signals initiating apoptosis are the death receptor ligands. Examples of such ligands are Tumour Necrosis Factor-alpha (TNF-alpha) which triggers apoptosis in certain cell types by binding to TNF receptors, such as TNFR1 and Fas Ligand (FasL) which binds to the Fas receptor (CD95). This latter pathway is particularly important in immune cell regulation. In addition to such proapoptotic ligands, some growth factors can act as survival factors actively suppressing apoptosis. Examples include Nerve Growth Factor (NGF) and Epidermal Growth Factor (EGF), withdrawal of which induces apoptosis in neurons and certain epithelial cells, respectively. Another major extracellular survival factor is the insulin-like growth factor IGF-1 which regulates the survival of several cell types. IGF-1 supports the survival and axonal sprouting of neurons in the central nervous system, protecting neurons after injury. IGF-1 also plays a role in the survival and function of heart muscle cells (cardiomyocytes), also promoting their growth and regeneration after injury, and acts as a survival factor for hepatocytes in the liver where it helps maintain liver tissue integrity and supports liver regeneration. Cell-matrix and cell-cell extracellular interactions also critically regulate apoptosis. Cell adhesion molecules (CAMs) expressed on the cell surface can transmit either pro- or anti-apoptotic signals by interacting with receptors on adjacent cells or by directly initiating intracellular signalling events. Loss of cell-matrix adhesion induces apoptosis through a process called anoikis, which helps maintain tissue integrity by eliminating cells that have lost contact with their extracellular matrix, thereby preventing the survival and spread of cells that have become detached from their original tissue environment. Cell-cell contact also plays a crucial role in regulating cell survival and inhibiting apoptosis through several mechanisms. Firstly, cell-cell contact can activate signalling pathways that promote cell survival and inhibit apoptosis. Binding of cell adhesion molecules such as integrins to the extracellular matrix or to other cells can trigger the activation of survival pathways, including the PI3K/Akt and MAPK/ERK pathways that promote the expression of anti-apoptotic proteins and inhibit the activation of pro-apoptotic factors. Cell-cell contact can also induce the release of survival factors or cytokines such as EGF, FGF and TGF-β from neighbouring cells, which can activate survival signals in the recipient cell. Activation of these survival signals can lead to the upregulation of anti-apoptotic proteins and the suppression of pro-apoptotic factors. Cell-cell contact can also directly inhibit apoptotic signalling pathways. For example, contact-mediated signalling can block the activation of death receptors, such as Fas or tumor necrosis factor receptor (TNFR), which normally initiate apoptotic pathways, whilst interaction between cell surface receptors on adjacent cells can also interfere with the binding of death ligands to their receptors, thereby preventing the activation of pro-apoptotic signalling cascades. Finally, immune cells, such as cytotoxic T cells and natural killer (NK) cells, can directly induce apoptosis via an extracellular mechanism in target cells. These cells can recognize specific molecules on the surface of target cells, such as viral antigens or abnormal proteins, and release cytotoxic granules containing enzymes (e.g., perforin and granzymes) that initiate the apoptotic process. We provide a comprehensive product range of research reagents for investigating extracellular apoptotic signals, including Granzyme B antibodies, Daxx antibodies, TRAIL antibodies, BAFF ELISA Kits, and Granzyme B ELISA Kits. Explore our full extracellular apoptotic signals product range below and discover more, for less. Alternatively, you can explore our Death Ligands and Granzymes product ranges.