Cytokines and Chemokines
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Introduction
Chemokines are a superfamily of small polypeptides that selectively control activation, adhesion, and chemotaxis of various leukocyte populations. More than 50 chemokines and 15 chemokine receptors have been described.
Different cell types express different chemokine receptors.
Some are primarily involved in inflammatory processes, while others are constitutialey expressed and play homeostatic roles.
Chemokines normally expressed in lymphoid organs or non-lymphoid tissues such as the skin direct normal trafficking.
Inflammatory chemokines
Pro-inflammatory cytokines such as TNF or IL-1 upregulate the expression of inflammatory chemokines such as IL-8. These signals are critical for phagocytic leukocyte and lymphocyte activation, extravasation, and chemotactic migration.
Chemotaxis of leukocytes follows extravasation and penetration of extracellular tissues.
Chemotaxis can be induced by many substances, both endogenous and exogenous:
- LPS
- peptides containing N-formyl-methionine
Chemotactic products appear to bind to GPCRs and induce cytoskeletal reorganization, mediated by Rac/Rho/Cdc42 GTPases.
Cytokines
Cytokines are important proteins that are mediate cell-cell communication in the immune system.
Cytokines can be divided into interleukin, chemokine, and growth factor families.
Cytokine Functions
- growth and behaviour of B Cells,
- CD8+ cells
- macrophages
- , and various other cells related to the immune response.
CD4+ cells, once activated, are an important producer of specific patterns of cytokines that are used to respond to various threats. This is eapecially important in mediating the immune response to infection of host cells to bacteria and protozoa.
Specific Cytokines
- Interferon gamma
- Interleukin-1
- Interleukin-2
- Interleukin-4
- Interleukin-8
- Interleukin-10
- Interleukin-12
- Tumor Necrosis Factor
Resources and References
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