Fig. 4

Overview and Pathways of the Complement System. The complement cascade involves a multitude of protein interactions occurring within the plasma, within the cells, and membranes. This process is initiated through the classical, lectin, and alternative pathways. These three pathways ultimately converge at C3, a pivotal mediator with diverse functions. The accompanying image highlights points of therapeutic intervention indicated by C3 (in red) and C5 (in blue) inhibition (Reprinted from Kim BJ, Mastellos DC, Li Y, Dunaief JL, Lambris JD. Targeting complement components C3 and C5 for the retina: Key concepts and lingering questions. Prog Retin Eye Res. 2021;83:100936, with permission from Elsevier)