Fig. 2
From: AMD and the alternative complement pathway: genetics and functional implications
The alternative complement pathway and the formation of the C3 convertase. In the AP, the generation of C3b can occur by either spontaneous hydrolysis of C3 (“tick-over” allowing for continuous low-level activation) or by plasma proteolytic cleavage all allowing for immediate C3b deposition. C3b forms the C3 convertase upon binding to FB and cleavage by FD resulting in an amplification loop producing additional C3b to stimulate a large immune response. C3b additionally binds to the C3 convertase leading to the formation of the C5 convertase initiating the terminal pathway and the establishment of the MAC. This figure was prepared using Servier Medical Art (http://www.servier.com/Powerpoint-image-bank)