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'''Mediating and regulating adaptive immunity''': in response to specific recognition by T lymphocytes, cytokines are produced that have a wide range of functions, including:

'''Mediating and regulating adaptive immunity''': in response to specific recognition by T lymphocytes, cytokines are produced that have a wide range of functions, including:

*regulating the growth and differentiation of some lymphocyte populations

*regulating the growth and differentiation of some lymphocyte populations

*recruitment, activation and regulation of specialised effector cells, e.g. mononuclear phagocytes, neutrophils, eosinophils

*recruitment, activation and regulation of specialised effector cells, e.g. mononuclear phagocytes, [[Neutrophils - WikiBlood|neutrophils]], eosinophils

'''Stimulating haematopoiesis''': produced primarily by bone marrow stromal cells and leukocytes, these cytokines stimulate the growth and differentiation of immature leukocytes.

'''Stimulating haematopoiesis''': produced primarily by bone marrow stromal cells and leukocytes, these cytokines stimulate the growth and differentiation of immature leukocytes.

By binding onto specific receptors on cell membranes, cytokines are able to exert their actions by triggering signal-cascade mechanisms that ultimately result in altered gene expression. Cytokines have an incredibly high affnity for their receptors, and are therefore able to act at picomolar concentrations. Cytokines can exert antagonistic effects on each other.

By binding onto specific receptors on cell membranes, cytokines are able to exert their actions by triggering signal-cascade mechanisms that ultimately result in altered gene expression. Cytokines have an incredibly high affnity for their receptors, and are therefore able to act at picomolar concentrations. Cytokines can exert antagonistic effects on each other.

==Important cytokines==

==Important cytokines==

Cytokines primarily produced by '''macrophages''':

Cytokines primarily produced by '''macrophages''':

*GM-CSF (granulocyte macrophage colony stimulating factor)- stimulates growth and differentiation of granulocytes, macrophages, neutrophils and eosinophils

*GM-CSF (granulocyte macrophage colony stimulating factor)- stimulates growth and differentiation of granulocytes, macrophages, [[Neutrophils - WikiBlood|neutrophils]] and eosinophils

*IL-1- stimulates Th2 cells and acute phase response

*IL-1- stimulates Th2 cells and acute phase response

*IL-6- stimulates growth and differentiation of B and T cells and acute phase response

*IL-6- stimulates growth and differentiation of B and T cells and acute phase response

*IL-5- stimulates eosinophil growth and differentiation

*IL-5- stimulates eosinophil growth and differentiation

*IL-10- suppresses macrophage functions

*IL-10- suppresses macrophage functions

Although neutrophils produce a lower amount of cytokines per cell than other immune cell types, they are often the first and most common cell type present at sites of infection. This makes them a physiologically important source of cytokines, such as IL-12.  

Although [[Neutrophils - WikiBlood|neutrophils]] produce a lower amount of cytokines per cell than other immune cell types, they are often the first and most common cell type present at sites of infection. This makes them a physiologically important source of cytokines, such as IL-12.  

==Chemokines==

==Chemokines==

The chemokines are a superfamily of cytokines, all related in terms of sequence and gene structure. The family is also known as the 'small cytokine' family (scy) or the intercrines. All have a relatively small molecular weight of ~5-10kDa and can be divided in one of two groups based on the position of the cystein residues (important for the tertiary structure):

The chemokines are a superfamily of cytokines, all related in terms of sequence and gene structure. The family is also known as the 'small cytokine' family (scy) or the intercrines. All have a relatively small molecular weight of ~5-10kDa and can be divided in one of two groups based on the position of the cystein residues (important for the tertiary structure):