Cytokine

Cytokines (/ˈsaɪtəkaɪn/)[1] are a broad and loose category of small proteins (~5–25 kDa[2]) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells, as well as endothelial cells, fibroblasts, and various types of connective tissue cells. A single cytokine may be produced by more than one type of cell.[3][4]

Cytokines are usually too large to cross cell membranes and enter cells. They typically function by interacting with specific cytokine receptors on the surface of target cells. Cytokines include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but generally not hormones or growth factors (despite some overlap in the terminology).

Cytokines are especially important in the immune system, including in immune responses and inflammation. Cytokines modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and responsiveness of particular cell populations. Some cytokines enhance or inhibit the action of other cytokines in complex ways. Cytokines are generally released in lower concentrations than hormones. Immune cytokines released by one cell can send signals to the same cell (autocrine signaling), nearby cells (paracrine signaling), and other cells throughout the body (endocrine signaling).

  1. ^ "CYTOKINE". dictionary.cambridge.org. Retrieved 27 September 2024.
  2. ^ Janeway's Immunobiology. Garland Science. 2017. p. 107. ISBN 978-0-8153-4551-0.
  3. ^ Lackie J (2010). "Cytokines". A Dictionary of Biomedicine. Oxford University Press. ISBN 978-0-19-954935-1.
  4. ^ "Cytokine". Stedman's Medical Dictionary (28th ed.). Wolters Kluwer Health, Lippincott Williams & Wilkins. 2006. ISBN 978-0-7817-6450-6.
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