Cytokines: production, local action and pleiotropy
THE CONTEXT
Cytokines are hormone-like substances that act at very low concentrations and influence several cell types.
Production and potency
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Cytokines are active even at femtomolar concentrations.
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Unlike endocrine hormones produced by specialised glands, cytokines are produced by widely distributed cells, including lymphocytes, macrophages, platelets and fibroblasts.
Sites of action
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Cytokines act locally near their producing cells through a paracrine effect.
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They can also act directly on their producing cells through an autocrine effect.
Range of effects and characterisation
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Cytokines are generally pleiotropic, having multiple effects on the growth and differentiation of various cell types.
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Different cytokines show considerable overlap in their effects.
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Cloning of cytokines and the availability of monoclonal antibodies against them have helped their characterisation.