Complement is defined as key part of innate immunity and as the first line of defense in the fight against invading pathogens. Complement 3 (C3) is the most abundant component of the complement cascade and the convergent point for all three major complement activation pathways: namely classical, alternative and mannose-binding lectin pathways. Complement activation leads to the formation of the C3 convertase, which cleaves C3 into the key effector molecules, C3a (anaphylatoxin) and C3b (opsonin) which then drive microbe removal. By binding to C3a receptor (C3aR), C3a exhibits potent anaphylatoxin activity, including increased vascular permeability, triggering degranulation of mast cells, inflammation, and activating leukocytes.