NCIt definition : A protein complex composed of five activated complement proteins that form a transmembrane
pore in pathogen cell membranes. Formation of the complex is initiated by C5 convertase
cleavage of complement C5 that yields C5b. C5b forms a complex with C6 and then C7;
this initial complex has an exposed hydrophobic site that can insert into the pathogen's
cell membrane. Then the trimeric C8 is recruited to the complex and the C5b-6-7-8
complex promotes the polymerization of 10-16 molecules of C9, which form the pore.
If enough of these pores penetrate the cell membrane of the pathogen, the targeted
cell will lyse and die.;
Alternative definition : CDISC: A protein complex composed of five activated complement proteins (C5b, C6,
C7, C8 and C9) and a cytolytic effector of innate and adaptive immunity, which may
be the target of autoantibodies. MAC forms pores in the plasma membrane of pathogens
or targeted cells, leading to osmolysis and cell death.;