Table 1.
Main complement regulators.
| Regulator | Abbreviation | Target pathway | Functions |
|---|---|---|---|
| Fluid phase regulators: | |||
| C1-inhibitor | C1-INH | CP and LP | Inhibits C1r, C1s, MASP-1 and MASP-2 proteolytic activities |
| MBL/ficolin-associated protein 1 | MAP-1 | LP | Binds MBL and ficolins and inhibits C4 deposition |
| Factor I | FI | CP, LP and AP | Cleaves C3b and C4b in their inactive fragments |
| C4 binding protein | C4BP | CP and LP | Accelerates decay of classical and lectin C3 convertase along with FI |
| Factor H | FH | AP | Accelerates decay of alternative C3 convertase along with FI |
| Carboxypeptidase N | CP, LP and AP | Inactivates C3a and C5a anaphylatoxin | |
| Membrane-bound regulators: | |||
| CR1 | CP, LP and AP | Binds C3b,C4b and C1q to promote phagocytosis of immune-complexes and accelerates decay of convertases | |
| CD46 | CP, LP and AP | Binds C3b and C4b accelerating decay of C3 convertase, cofactor for FI | |
| CD55 | CP, LP and AP | Accelerates decay of C3 convertases | |
| Complement receptor 1-related protein y | Crry | CP, LP and AP | Cleaves C3b and C4b inhibiting C3 convertases formation, cofactor for FI |
| CD59 | CP, LP and AP | Binds C8 and C9 preventing the assembly of C5b-9 lytic complex |
CP, classical pathway; LP, lectin pathway; AP, alternative pathway.