Complement System


Alternative Pathway
  • The alternative pathway uses factors B, D and P in the process of activating C3 to C3b.
  • It does not require the presence of antibody/antigen reaction.
Common Pathway
  • The common pathway has C3b cleaving C4 to C4a and C4b. C4b cleaves C5 to C5a and C5b.
  • Both C4a and C5a join C3a and are all anaphylatoxins.
  • C5b will lead to the membrane attack complex C5b678 which works to insert C9 pieces into the plasma membrane of a cell to cause osmolysis. It is also a chemotactic agent.