Anaphylatoxin

Small fragments of Complements are called anaphylatoxins. They are formed during Complement activation, and are able to bind to so-called "anchor residues" of MHC class I molecules. They are potent and effective chemoattractants and cell activators by inducing the release of a number of cytokines, chemokines, and inflammatory mediators. In synergy with other pro-inflammatory factors, such as lipopolysaccharide (LPS) or tumor necrose factor (TNF) they can cause severe effects, e.g. septic shock or the acute respiratory distress syndrome (ARDS). The most important anaphylatoxins are C5a and C3a. They are heat stable, 10 kD fragments of the amino terminus of the alpha chain of complement components C3 and C5, respectively. C3a and C5a interact with the C3a receptor or C5a receptor, respectively, to cause their biological effects. C4a is sometimes also included in the term anaphylatoxin, but is less potent than C3a and C5a.

Anaphylatoxins

Complement and Allergy