Table 1.
Complement regulators
| Regulator | Ligand | Function |
|---|---|---|
| Soluble regulators | ||
| Factor H (FH) | C3b, C3d | AP C3 convertase decay and cofactor |
| FHL‐1 | C3b | AP C3 convertase decay and cofactor |
| CFHR1 | C3b, C3d, C5 convertase | Inhibits C5 convertase, competes with FH, acts as decoy for certain pathogens |
| CFHR2 | C3b, C3d, AP C3 convertase | AP C3 convertase decay, competes with FH |
| CFHR3 | C3b, C3d | Competes with FH |
| CFHR4 | C3b | AP C3 convertase decay |
| CFHR5 | C3b, C3/C5 convertase? | Competes with FH |
| Factor I (FI) | Cofactor bound C3b and C4b | Serine protease, degrades C3b, iC3b, C4b, and iC4b |
| Properdin (FP) | C3b, C3bB, C3bBb, GAGs | Stabilizes AP convertases |
| C4BP | C4b, S protein | CP C3 convertase decay and cofactor |
| C1‐INH | C1r, C1s, MASPs | Serine protease inhibitor |
| MAp19 | MBL and ficolins | Competes with MASP‐2 in vitro |
| MAp44 | MBL and ficolins | Blocks MASP transactivation |
| Clusterin | C7, C8, C9, MAC | Inhibits MAC |
| Vitronectin | C5b‐C7, MAC, GAGs | Inhibits MAC |
| Membrane‐associated and transmembrane regulators | ||
| MCP (CD46) | C3b, C4b | Cofactor activity, T‐cell differentiation and activation |
| DAF (CD55) | C3b, C4b, AP and CP C3 convertase | AP and CP C3 convertase decay |
| CD59 | C8, MAC | Inhibits MAC |
| CR1 | C3b, C4b | AP and CP C3 convertase decay and cofactor |