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.
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.
Some studies have shown links between cytokine levels and Clinical depression .
In the inflammatory response, white blood cells release cytokines, which also recruit more lymphocytes and allow them to pass through blood vessel walls into the inflamed area (Clark, 2005). Their release triggers stages in the wound healing cascade. They are also implicated in brain tissue damage due to Reperfusion injury in Stroke (Clark, 2005).
Most cytokines are not growth factors.