Immunological Perspective of Complement

The complement system functions as a link between innate and acquired immunity and is a crucial component of the innate immune response. It is made up of a number of proteins that are mostly synthesized in the liver and exist as precursors only in plasma and on cell surfaces. Through a coordinated sequential enzyme cascade that clears foreign cells through pathogen detection, opsonization, and lysis, complement mediates responses to inflammatory stimuli. Additionally, complement has anti-inflammatory properties. It binds to immune complexes and apoptotic cells and helps remove them from the bloodstream and injured tissues. IgG and IgM antibodies activate and collaborate with complement proteins, giving rise to the term "complement." Numerous complement proteins are present in a "precursor" state and become active when there is inflammation. The creation of successive non-covalently linked activated protein fragments makes the complement system more complicated than many enzyme cascades.