Cytokines are biologically active mediators with regulatory effects on other cells.
Definition and included mediators
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Cytokines are biologically active substances released by activated T lymphocytes.
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They include interleukins, interferons, growth factors and other substances with similar effects. Interleukins are described as leucocyte products that regulate other cells.
Evolution of terminology
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These substances were originally called lymphokines; similar substances produced by monocytes or macrophages were called monokines.
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Early names reflected demonstrated biological effects. The broader term cytokines was adopted because individual lymphokines have multiple effects, different lymphokines can produce the same effect, and the former names lacked precision.