plasma proteins that coat the outside of pathogens and make them easier to phagocytize
a cascade of proteases that activate complement (called zymogens when inactive)
C3 (C3a and C3b)
The most important component of compliment.
C3b fragment undergoes complement fixation and binds to a bacteria and tags it for destruction or starts a MAC.
C3a acts as a chemoattractant and recruits effectors.
iC3 or CB(H2O) involves no cleavage just the association of one water molecule .
cleaved by factor D into Bb and Ba
Bb has protease properties and binds to iC3 to for iC3Bb
iC3Bb binds to other C3s and cleaves into C3a and C3b. iC3Bb is soluble
Alternative C3 Convertase
C3bBb - works/binds to the surface of the pathogen and does not diffuse away like C3 convertase, so a larger portion of the C3b affix to the cell surface for marking. This positive feedback amplifies C3 cleavage.