Table 1

A summary of the three branches of the complement activation pathway

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


Nonaka and Miyazawa Genome Biology 2001 3:reviews1001.1-reviews1001.5   doi:10.1186/gb-2001-3-1-reviews1001