CD8

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.

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.

Role in Immune Response

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.

Clinical Significance

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.

See Also

• T cell
• Cytotoxic T cell
• Natural killer cell
• MHC class I
• Antigen presenting cell
• Cytokine
• HIV
• Autoimmune disease

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