In this complement pathway, no antigen-antibody reaction is required. Also Cl*C4*C2 (as in the classical cascade) is by-passed and complement binding starts at C3. The alternative pathway can be triggered by several factors, including bacterial membrane polysaccharides, bacterial endotoxins, and cobra venom. In general, this pathway allows bacteria to be destroyed without having pre-formed antibody directed against them.
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| Alternate (Properdin) Pathway |