Cell-mediated

Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

Overview

Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells. It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria. It also plays a major role in transplant rejection.

Mechanism

The process of cell-mediated immunity is complex and involves many types of cells, notably T cells and macrophages. Antigen-presenting cells (APCs) present antigens on their surfaces to cytotoxic T cells. These T cells are activated when their T-cell receptor (TCR) binds to this specific antigen in a complex with the MHC Class I receptor of the APC. This event primes the T cell, which then differentiates into a cytotoxic T cell. The cytotoxic T cell then travels throughout the body in search of cells where the MHC I receptors bear this antigen. When it finds such a cell, it induces cell death.

Role in disease

Cell-mediated immunity plays a key role in controlling and eliminating intracellular pathogens. However, it can also contribute to immune pathology of diseases and to autoimmune disorders.

See also

• Humoral immunity
• Adaptive immune system
• Innate immune system

References

Cell-mediated Resources
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