Editing Programmed cell death (section)

===== Extrinsic Pathway =====
{{See also|Activation-induced cell death}}
The extrinsic pathway involves specific receptor ligand interaction. Either the FAS ligand binds to the FAS receptor or the TNF-alpha ligand can bind to the TNF receptor. In both situations there is the activation of initiator caspase. The extrinsic pathway can be activated in two ways. The first way is through fast ligan TNF-alpha binding or through a cytotoxic t-cell. The cytotoxic T-cell can attach itself to a membrane, facilitating the release of granzyme B. Granzyme B perforates the target cell membrane and in turn allows the release of perforin. Finally, perforin creates a pore in the membrane, and releases the caspases which leads to the activation of caspase 3. This initiator caspase may cause the cleaving of inactive caspase 3, causing it to become cleaved caspase 3. This is the final molecule needed to trigger cell death.<ref>{{Cite web |title= Apoptosis &#124; Intrinsic and extrinsic pathway &#124; USMLE step 1 &#124; Pathology| website=[[YouTube]] | date=8 January 2023 |url=https://www.youtube.com/watch?v=fwXpI6HdaZo.}}</ref>