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'''CD8''' is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor (TCR). It is primarily expressed on the surface of cytotoxic T cells and natural killer cells.
== CD8 T Cells ==
 
[[File:CD8_receptor.svg|thumb|right|Diagram of the CD8 receptor]]
 
'''CD8 T cells''', also known as '''cytotoxic T cells''', are a subset of [[T cells]] that play a crucial role in the [[immune system]] by directly killing infected or cancerous cells. These cells are characterized by the presence of the CD8 glycoprotein on their surface, which serves as a co-receptor that enhances their ability to recognize antigens presented by [[MHC class I]] molecules.


== Structure and Function ==
== Structure and Function ==


CD8 is a cell surface protein found on most cytotoxic T lymphocytes that mediates efficient cell-cell interactions within the immune system. The CD8 antigen acts as a co-receptor with the T-cell receptor on the T lymphocyte to recognize antigens displayed by an antigen presenting cell in the context of class I MHC molecules. The functional co-receptor is either a homodimer composed of two alpha chains, or a heterodimer composed of one alpha and one beta chain. Both alpha and beta chains share significant homology to immunoglobulin variable light chains.
CD8 T cells are distinguished by the CD8 receptor, which is a dimeric protein composed of two chains, usually referred to as CD8_ and CD8_. This receptor is essential for the interaction with MHC class I molecules, which present endogenous antigens, typically derived from viral or tumor proteins.
 
The primary function of CD8 T cells is to eliminate cells that are infected with viruses or have become cancerous. Upon recognition of an antigen-MHC class I complex, CD8 T cells become activated and can induce apoptosis in the target cell through the release of cytotoxic granules containing [[perforin]] and [[granzymes]].


== Role in Immune Response ==
== Activation and Differentiation ==


CD8+ T cells are crucial in the immune response against intracellular pathogens, cancer, and in the control of autoimmunity. They recognize antigens presented by MHC class I molecules on the surface of infected or malignant cells and kill these cells directly. CD8+ T cells also produce a variety of cytokines that influence the activity of other cells involved in the immune response.
CD8 T cell activation requires two signals: recognition of the antigen-MHC class I complex and a co-stimulatory signal provided by [[antigen-presenting cells]] (APCs). Once activated, CD8 T cells proliferate and differentiate into effector cells capable of killing target cells. Some of these cells will also become [[memory T cells]], which provide long-term immunity by responding more rapidly upon re-exposure to the same antigen.


== Clinical Significance ==
== Role in Disease and Therapy ==


Changes in the number and function of CD8+ T cells are associated with a variety of diseases. For example, a decrease in CD8+ T cells is seen in HIV infection, while an increase is seen in certain autoimmune diseases. CD8+ T cells are also the target of several therapeutic strategies in cancer and infectious diseases.
CD8 T cells are critical in controlling viral infections and are also involved in the immune response against tumors. However, their activity can also contribute to [[autoimmune diseases]] if they mistakenly target healthy cells. In [[cancer immunotherapy]], strategies such as [[CAR T-cell therapy]] aim to enhance the activity of CD8 T cells against cancer cells.


== See Also ==
== Related pages ==


* [[T cell]]
* [[T cell]]
* [[Cytotoxic T cell]]
* [[Natural killer cell]]
* [[MHC class I]]
* [[MHC class I]]
* [[Antigen presenting cell]]
* [[Immune system]]
* [[Cytokine]]
* [[Cytotoxicity]]
* [[HIV]]
* [[Cancer immunotherapy]]
* [[Autoimmune disease]]


[[Category:Immunology]]
[[Category:Immunology]]
[[Category:Cell biology]]
[[Category:Proteins]]
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Latest revision as of 03:49, 13 February 2025

CD8 T Cells[edit]

Diagram of the CD8 receptor

CD8 T cells, also known as cytotoxic T cells, are a subset of T cells that play a crucial role in the immune system by directly killing infected or cancerous cells. These cells are characterized by the presence of the CD8 glycoprotein on their surface, which serves as a co-receptor that enhances their ability to recognize antigens presented by MHC class I molecules.

Structure and Function[edit]

CD8 T cells are distinguished by the CD8 receptor, which is a dimeric protein composed of two chains, usually referred to as CD8_ and CD8_. This receptor is essential for the interaction with MHC class I molecules, which present endogenous antigens, typically derived from viral or tumor proteins.

The primary function of CD8 T cells is to eliminate cells that are infected with viruses or have become cancerous. Upon recognition of an antigen-MHC class I complex, CD8 T cells become activated and can induce apoptosis in the target cell through the release of cytotoxic granules containing perforin and granzymes.

Activation and Differentiation[edit]

CD8 T cell activation requires two signals: recognition of the antigen-MHC class I complex and a co-stimulatory signal provided by antigen-presenting cells (APCs). Once activated, CD8 T cells proliferate and differentiate into effector cells capable of killing target cells. Some of these cells will also become memory T cells, which provide long-term immunity by responding more rapidly upon re-exposure to the same antigen.

Role in Disease and Therapy[edit]

CD8 T cells are critical in controlling viral infections and are also involved in the immune response against tumors. However, their activity can also contribute to autoimmune diseases if they mistakenly target healthy cells. In cancer immunotherapy, strategies such as CAR T-cell therapy aim to enhance the activity of CD8 T cells against cancer cells.

Related pages[edit]