Anaphylatoxin
Chapter: 2
Proinflammatory mediators produced by activation of the complement cascade, either through the classical or alternative pathway. The anaphylatoxins include C3a, C4a, and C5a (Note that C4a can only be produced through the classical pathway, because alternative pathway activation of the complement cascade bypasses activation of C4. There is an apparent inconsistency in your text, p.48, where, under the heading "anaphylatoxins", it implies that they are products of the classical pathway, only. This is incorrect, a fact that is attested to in the paragraph above, wherein it clearly states that C3a and C5a can be produced via the alternative pathway.). Anaphylatoxins have several activities, including inducement of smooth-muscle contraction, increased vascular permeability, and degranulation of mast cells and basophils. C5a is one of the most potent chemotactic agents known, for a wide variety of inflammatory cell types. C5a also "primes" or readies neutrophils for various antibacterial functions, e.g., phagocytosis, as they move along the chemotactic gradient, toward higher concentrations of the mediator. This has the effect of increasing their effectiveness when they reach the inciting stimulus.
See Also: