Table 1 A summary of the three branches of the complement activation pathway
From: Evolution of the initiating enzymes of the complement system
| Â | Classical pathway | Lectin pathway | Alternative pathway |
|---|---|---|---|
Triggering factor | Antigen-antibody complexes | Mannan-binding lectin | Pathogen (directly) |
Proteases involved | C1r, C1s and C2 | MASP-1, MASP-2 and MASP-3 | Factor D and Factor B |