Last reviewed 01/2018

Complement component C5a has the following functions:

  • anaphylatoxin, promoting histamine release from mast cells and basophils, so increasing vascular permeability
  • increases the surface expression of leukocyte adhesion molecules on endothelium, so promoting leukocyte transit into the extracellular space
  • chemotactic agent for inflammatory leukocytes
  • promotes killing action of leukocytes
  • activates the lipoxygenase pathway of arachidonic acid metabolism in neutrophils and macrophages

C5a may be produced by the classical or alternative pathways, or, it may be a product of:

  • trypsin
  • bacterial proteases
  • lysosomal enzymes released from a variety of leukocytes