The membrane attack complex (MAC) is the cytolytic end product of the complement cascade, composed of one C5:C6:C7:C8 complex and 12 to 15 C9 molecules (Podack et al. 1982, Biesecker et al. 1993). 12 C9 molecules are represented in this reaction. C9 peptides polymerize to form a ring-shaped transmembrane channel, which causes osmotic lysis of the target cell (Kondos et al. 2010). While formation of a pore is typically associated with necrotic cell death, there is evidence of membrane permeabilization from MACs containing one C9 molecule per C5b–8 complex (Sims et al. 1983).
Podack, ER, Tschoop, J, Müller-Eberhard, HJ
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