Cytokine

Aka: Cytokine, Lymphokine, Monokine, Interferon, Chemokine, Tumor Necrosis Factor, Interleukin, Colony Stimulating Factor, Colony-Stimulating Factor

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II. Definitions

  1. Cytokine
    1. Derived from "cyto" (cell) and "kinesis" (movement)
    2. Glycoproteins act in inflammatory and immune response via cell to cell communication
    3. Released from cells in response to a trigger (e.g. Antigen binding) and bind and activate Target Cells
  2. Lymphokine
    1. Cytokines released from Lymphocytes
    2. Some Lymphokines are actually not produced by Lymphocytes (Cytokine is preferred term)
  3. Monokine
    1. Cytokines released from Monocytes and Macrophages
    2. Some Monokines are actually not produced by Monocytes and Macrophages (Cytokine is preferred term)

III. Physiology

  1. Cytokine-producing cell secretes Cytokine in response to trigger
  2. Cytokine regions of activity
    1. Autocrine Action
      1. Bind and act at the same cell that released the Cytokine
    2. Paracrine Action
      1. Bind and act at neighboring, local cells
    3. Endocrine Action
      1. Bind and act distant, systemic cells
  3. Cytokine function
    1. Cytokines are pleiotropic (multiple effects at different cells)
    2. Released Cytokine activity may be synergistic or Antagonistic (or redundant) to other released Cytokines

IV. Types

  1. Interleukin (IL)
    1. Group of more than 30 Cytokines that are released from Leukocytes
  2. Interferon (IFN)
    1. Cytokines released from Lymphocytes, Dendritic Cells, Macrophages, fibroblasts, Natural Killer Cells and T Cells
    2. Interferons inhibit tumor proliferation
      1. Synthetic Interferons are used to treat Hairy Cell Leukemia and AIDS-related Kaposi Sarcoma
    3. Interferon-alpha (leukocyte Interferon)
      1. Antiviral activity
      2. Class 1 MHC presentation
    4. Interferon-beta (fibroblast Interferon)
      1. Antiviral activity
      2. Class 1 MHC presentation
    5. Interferon-gamma (immune Interferon)
      1. Class 1 and 2 MHC presentation
      2. Increases Antigen Presentation
  3. Tumor Necrosis Factor (TNF, cachectin)
    1. Cytokines released from Macrophages (as well as other cells)
    2. Released in response to Bacterial Infections (esp. Gram Negative Bacteria)
    3. Acts at the Hypothalamus to induce fever
    4. Acts at the liver to release acute phase reactants
    5. Induces programmed cell death (apoptosis)
    6. Mediator in Septic Shock
    7. Originally identified as mediator of tumor necrosis (animals), Chronic Wasting Disease (cows, cachectin)
  4. Colony Stimulating Factor (CSF)
    1. Cytokines produced by Bone Marrow stems cells (as well as others including T Cells and Macrophages)
    2. Stimulate differentiation of progenitor cells
      1. Erythrocyte Colony-Stimulating Factor (Erythropoietin)
      2. Megakaryocyte Colony-Stimulating Factor (Thrombopoietin)
      3. Granulocyte Colony-Stimulating Factor (Pluripoietin)
      4. Macrophage Colony-Stimulating Factor
  5. Chemokines
    1. Group of more than 50 small molecule Cytokines regulating chemotaxis (inflammatory cell attraction)

V. Resources

  1. Immune System (Wikipedia)
    1. https://en.wikipedia.org/wiki/Cytokine

VI. References

  1. Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL
  2. Guyton and Hall (2006) Medical Physiology, p. 419-50

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