T cell apoptotic process

Definition

Target type: biologicalprocess

Any apoptotic process in a T cell, a type of lymphocyte whose defining characteristic is the expression of a T cell receptor complex. [CL:0000084, GOC:add, GOC:mtg_apoptosis, ISBN:0781765196]

T cell apoptosis is a tightly regulated process that eliminates T cells that are no longer needed or that could potentially harm the body. It is essential for maintaining immune homeostasis and preventing autoimmune diseases. T cell apoptosis can be triggered by a variety of stimuli, including:

* **Activation-induced cell death (AICD):** This is a process that occurs when T cells are chronically activated. Continuous stimulation of the T cell receptor (TCR) leads to the accumulation of pro-apoptotic proteins, such as Fas ligand (FasL) and TNF-related apoptosis-inducing ligand (TRAIL), on the T cell surface. These molecules then bind to their receptors on the same cell, triggering the apoptotic cascade.
* **Withdrawal of survival signals:** T cells require continuous stimulation by cytokines and other factors to survive. When these signals are withdrawn, T cells undergo apoptosis.
* **Cytokine deprivation:** The absence of certain cytokines, such as IL-2, can also trigger T cell apoptosis.
* **Exposure to cytotoxic T lymphocytes (CTLs):** CTLs are specialized T cells that kill other cells by releasing cytotoxic molecules. CTLs can kill T cells that are infected with viruses or other pathogens, or that are expressing tumor antigens.
* **Exposure to radiation or chemotherapy:** These treatments can damage T cells, leading to apoptosis.

The apoptotic process in T cells involves a series of biochemical events that ultimately lead to the dismantling of the cell. These events include:

* **Activation of caspases:** Caspases are a family of proteases that are essential for apoptosis. Caspase activation is initiated by a variety of stimuli, including death receptors and mitochondrial damage.
* **Mitochondrial dysfunction:** Mitochondria play a critical role in apoptosis. During apoptosis, the mitochondrial membrane potential collapses, leading to the release of cytochrome c and other pro-apoptotic factors into the cytosol.
* **DNA fragmentation:** The DNA of apoptotic cells is cleaved into fragments by a caspase-activated DNase called caspase-activated DNase (CAD).
* **Formation of apoptotic bodies:** The apoptotic cell breaks down into small, membrane-bound vesicles called apoptotic bodies. These bodies are then engulfed by phagocytes, preventing inflammation and the release of harmful cellular contents.

T cell apoptosis is a complex process that is tightly regulated by a variety of factors. It is essential for maintaining immune homeostasis and preventing autoimmune diseases. Dysregulation of T cell apoptosis can lead to a variety of diseases, including cancer, autoimmune disorders, and immunodeficiency.'
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