Chemical mediators of inflammation

This vast group are molecules produced for inter- and intracellular signalling.

They are intimately involved in the inflammatory and immune responses as both effectors and a means of co-ordinating the level of activity. Their interaction is undoubtedly complex and poorly understood. It is important to emphasise that in vitro activity does not necessarily equate with a role in vivo.

One means of classifying them is by tissue of origin:

• plasma-derived: inactive precursors produced in liver and circulate as plasma proteins. Activated by binding specific substance which then trigger proteolysis of the next plasma protein in sequence. Examples include:
  • kinin system
  • clotting system
  • fibrinolytic system
  • complement cascade
    
    
• tissue-derived: a diverse range of substances whose release is triggered by a number of stimuli e.g. direct injury, neurogenic stimuli, immune mechanisms or other inflammatory mediators. Examples include:
  • vasoactive amines: histamine and serotonin
  • eicosanoids - arachidonic acid metabolites
  • acute phase proteins
  • platelet activating factor
  • lysosomal constituents
  • cytokines
  • growth factors