Table 1.

Complement system regulators, function, and location within the system

Regulatory Protein	Regulatory Function	Type	References
CD59	Block C9 complex with C5bC6C7C8 to prevent MAC formation	Membrane Bound	33
Complement Receptor 1 (CR1)	Membrane bound cofactor for Factor I	Membrane Bound	24
CD55	Prevents C3 convertase formation by interaction with C3b and C4b	Membrane Bound	28
Membrane Cofactor Protein (MCP)	Membrane bound cofactor for Factor I	Membrane Bound	25
Thrombomodulin	Enchances Factor H. C3a C5a degredation	Membrane Bound	30
C1 Inhibitor (C1-INH)	Prevents induction of classical and MBL pathways by inactivating C1r and C1s, MASP’s	Plasma	27
C4 Binding Protein (C4BP)	Binds C4b. Prevents formation of C3 convertase in MBL and Classical Pathways	Plasma	22
Clusterin	Binds C5bC6C7 and inhibits binding of C9	Plasma	34
Factor H	Binds C3b on cell surface and triggers degredatation, preventing AP activation	Plasma	23
Factor I	Proteolytic cleavage of C3b and C4b	Plasma	26
CPN1	Degrades C3a and C5a	Plasma	29
Vitronectin	Binds C5bC6C7 and blocks C9 polymerization	Plasma	35