PYROGENIC CYTOKINES, Should I Know...?

 

Cytokines are small proteins (molecular mass, 10,000 to 20,000 Da) that regulate immune, inflammatory, and hematopoietic processes. For example, stimulation of lymphocyte proliferation during an immune response to vaccination is the result of the cytokines interleukin (IL) 2, IL-4, and IL-6. Another cytokine, granulocyte colony-stimulating factor, stimulates granulocytopoiesis in the bone marrow. Some cytokines cause fever and hence are called pyrogenic cytokines. From a historic point of view, the field of cytokine biology began in the 1940s with laboratory investigations into fever induction by products of activated leukocytes. These fever-producing molecules were called endogenous pyrogens. The known pyrogenic cytokines include IL-1, IL-6, tumor necrosis factor (TNF), ciliary neurotropic factor (CNTF), and interferon (IFN) α. Others probably exist, although IL-18—a member of the IL-1 family—does not appear to be a pyrogenic cytokine. Each cytokine encoded by a separate gene, and each pyrogenic cytokine has been shown to cause fever in laboratory animals and in humans. When injected into humans, IL-1, IL-6, and TNF produce fever at low doses (10 to 100 ng/kg).

The synthesis and release of endogenous pyrogenic cytokines are induced by a wide spectrum of exogenous pyrogens, most of which have recognizable bacterial or fungal sources. Viruses also induce pyrogenic cytokines by infecting cells. However, in the absence of microbial infection, inflammation, trauma, tissue necrosis, or antigenantibody complexes can induce the production of IL-1, TNF, and/or IL-6, which—individually or in combination—trigger the hypothalamus to raise the set point to febrile levels. The cellular sources of pyrogenic cytokines are primarily monocytes, neutrophils, and lymphocytes, although many other types of cells can synthesize these molecules when stimulated.
Source: Harrison_s_Principles_of_Internal_Medicine_16th_Edition