Immune cells can initiate apoptosis through both the intrinsic and extrinsic pathways, depending on the context and the specific immune cell involved. For example, cytotoxic T lymphocytes (CTLs) can induce apoptosis in target cells through the release of granules containing perforin and granzymes. Perforin creates pores in the target cell membrane, allowing granzymes to enter and activate the caspase cascade, leading to apoptosis via the intrinsic pathway. Natural killer (NK) cells can also induce apoptosis in target cells through the release of perforin and granzymes, as well as through the engagement of death receptors on the target cell surface via the extrinsic pathway. In addition, various immune cells can undergo apoptosis themselves as a mechanism of self-regulation and immune tolerance, and this process can be mediated by both intrinsic and extrinsic pathways. Overall, the decision to undergo apoptosis in immune cells is regulated by a complex interplay of signaling pathways, including those involving cytokines, growth factors, and cell adhesion molecules, as well as the balance between pro- and anti-apoptotic signals.