Cytokine
From Freepedia
Cytokines are small protein molecules that are the core of communication between immune system cells, and even between these cells and cells belonging to other tissue types. They are actively secreted by immune cells as well as other cell types in response to external stimuli. Cytokines that are produced by immune cells form a subset known as lymphokines. Their action is often local, but sometimes can have effects on the whole body. The first lymphokines were identified in the mid-1960's, with the best known being migration inhibition factor (MIF), simultaneously discovered by John David and Barry Bloom. The first cytokines were identified in cultures of kidney cells, by Stanley Cohen and his colleagues, in 1974.
Cytokines are said to be pleiotropic, meaning that the same cytokine can have different effects on a cell depending on the state of the cell. For instance, there are several known cytokines that have both stimulating and suppressing action on lymphocyte cells and immune response.
To make things even more complicated, cytokines often regulate the expression of other cytokines (either upwards or downwards), often triggering cascades of other cytokines. The cytokines in these cascades can interact with each other and the cells that produced them in complicated fashions to form cytokine networks. Cytokines often act together in ways that are synergistic or antagonistic.
Hundreds of cytokines have been discovered, and the rate of discovery shows no sign of slowing. Some of the better known cytokines include: TNF-α, IL-1, and IL-6. There are three classes of cytokines.
Cytokines act by binding to their cell-specific receptors. These receptors are located in the cell membrane and each allows a distinct signal transduction cascade to start in the cell, that eventually will lead to biochemical and phenotypical changes in the target cell. Typically, receptors for cytokines are also tyrosine kinases.
Most cytokines are not growth factors.
Cytokines mediate many important physiological functions including growth, development, wound healing and immune response.
Some studies have shown links between cytokine levels and clinical depression [1].
See also
- Adipokines
- Apoptosis
- Chemokines
- Cytokine storm
- Interleukins
- Interferon
- Granulocyte-colony stimulating factor
- Signal transduction
- Tumor necrosis factor
- ELISPOT
external links
- http://www.copewithcytokines.de Cytokines Online Pathfinder Encyclopaedia
