T cell
Say it: TEE sel
A T cell is a white blood cell that matures in the thymus and drives cell-based immunity, directing other immune cells or killing infected cells.
Also: T lymphocyte, T cells
Definition
What is a T cell?
T cells, or T lymphocytes, are white blood cells of the adaptive immune system. They start out as bone marrow stem cells but finish developing in the thymus, the organ that gives them their letter. There, each cell builds a unique T cell receptor. Cells that cannot recognize the body's MHC molecules die, and those that react strongly to the body's own molecules are destroyed, so only a small fraction survive to leave the thymus.
A T cell receptor cannot bind a free antigen; it recognizes a short peptide fragment displayed on an MHC molecule on another cell's surface. The main types differ in their coreceptors and jobs. Helper T cells carry CD4, recognize antigen on MHC class II and release cytokines that direct other immune cells. Cytotoxic T cells carry CD8, recognize antigen on MHC class I and kill infected or cancerous cells by triggering apoptosis. Regulatory T cells restrain responses and help prevent autoimmunity, and memory T cells remain after an infection to respond faster next time.
T cells drive transplant rejection and are central to newer cancer immunotherapies.
Word parts
Where does the term “T cell” come from?
- lympho-
- lymph, the clear fluid of the lymphatic systemLatin lympha, water
- -cyte
- cellGreek kytos, hollow vessel
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Related
Terms that go with it
- Helper T cellA helper T cell is a CD4 T lymphocyte that coordinates immune responses, releasing cytokines that activate B cells, killer T cells and macrophages.
- Cytotoxic T cellA cytotoxic T cell is a white blood cell of adaptive immunity that finds and kills body cells infected by viruses or turned cancerous.
- Major histocompatibility complexThe major histocompatibility complex is a set of genes whose proteins display protein fragments on cell surfaces so that T cells can inspect them.
- Adaptive immunityAdaptive immunity is the branch of the immune system that learns to recognize specific antigens and remembers them, so it responds faster next time.
- White blood cellA white blood cell, or leukocyte, is any of the nucleated immune cells in blood that defend the body against infection and clear away debris.
- B cellA B cell is a lymphocyte, a kind of white blood cell, that produces antibodies and forms a key part of the adaptive immune system.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- NCI Dictionary of Cancer Terms: T cell
- OpenStax Anatomy and Physiology 2e, 21.3 The Adaptive Immune Response: T Lymphocytes and Their Functional Types
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