Table 2:
| Regulator | Target | Function | Pathway | Location |
|---|---|---|---|---|
| C1-INH | C1qrs, MASPs | Inactivates C1r and C1s, MASP-1 and MASP-2 | CP/LP | Fluid |
| Small mannose-binding lectin-ficolin-associated protein (sMAP, MAP19) | MBL | Competes with MAPS1–3 | LP | Fluid |
| Mannose-binding lectin-ficolin-associated protein-1 (MAP-1) | MBL/ficolins | Competes with MAPS | LP | Fluid |
| C4BP | C4b | Inhibits C3 convertase | CP/LP | Fluid |
| Factor H | C3b, Factor B, Bb | Blocks the formation of C3 convertases | CP/LP/AP | Membrane and fluid |
| Factor H-related proteins 1–5 | C3b, Factor H | Competes with factor H | CP/AP | Membrane and fluid |
| Factor I | C3b,C4b | Degrades C3b or C4b with cofactor | CP/LP/AP | Fluid |
| CR1 | C3b,C4b | Inhibits C3/C5 convertase | CP/LP/AP | Membrane |
| CD46 (MCP) | C3b,C4b | Inhibits C3/C5 convertase. Cofactor for Factor I. |
CP/LP/AP | Membrane |
| CD55 (DAF) | C3b,C4b, C3convertase | C3/C5 convertase decay | CP/LP/AP | Membrane |
| Signal Regulatory Protein α (SIRPα and family) | MAC-1(CR3) | Inhibits phagocytosis | CP/LP/AP | Membrane |
| Crry | C3/C5 convertase | Inhibits C3/C5 convertase | CP/LP/AP | Membrane |
| vWF | C3b | Helps with C3b cleavage | CP/LP/AP | Fluid |
| Thrombomodulin (CD141) | C3a, C3b, C4b, C5a | C3/C5 convertase decay. Anaphylatoxin inhibitor | CP/LP/AP | Membrane and fluid |
| Plasmin(ogen) | C3, C3b, C3d, and C5 | C3/C5 convertase decay | CP/LP/AP | Membrane and fluid |
| Carboxypeptidase N, R, B (thrombin-activatable fibrinolysis inhibitor) | C3a, C5a | Anaphylatoxin inhibitor | CP/LP/AP | Fluid |
| Cartilage oligomeric matrix protein (thrombospondin 5) | C1q, MBL | Inhibits C3 convertase | CP/LP | Fluid |
| C3, Properdin | Activates AP | AP | Fluid | |
| CUB (structural motif consistsof C1r/C1s, Uegf, Bmp1) and sushi multiple domains 1 (CSMD1) | C3b, C4b | Cofactor of Factor I? | CP/LP? | Membrane |
| Sushi domain-containing protein 4 (SUSD4) | C1q, MBL, C3b? | Inhibits C3 convertase | CP/LP/AP | Membrane and fluid (?) |
| Clusterin (apolipoprotein J, SP-40) | C5b-8 | Inhibits MAC formation | TP | Fluid |
| Vitronectin (VN, S-protein, S40) | C5b-9 | Inhibits MAC formation | TP | Fluid |
| CD59 (HRF20, protctin) | C8, C9 | Inhibits MAC formation | TP | Membrane |
Abbreviations: AP = Alternative pathway; C1-INH = C1 inhibitor; C4BP = C4-binding protein; CR1 = Complement receptor 1 (CD35); CP = Classical pathway; Crry = Complement receptor-related protein, expressed in mouse and rat; DAF = CD55, decay-accelerating factor; LP = Lectin pathway; MASP = Mannose-binding lectin-associated serine proteases; MBL = Mannose-binding lectin; MCP = CD46, membrane cofactor protein; TP = Terminal pathway; vWF = von Willebrand factor.