ⓘ Complement system
The complement system, also known as complement cascade, is a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogens cell membrane. It is part of the innate immune system, which is not adaptable and does not change during an individuals lifetime. The complement system can, however, be recruited and brought into action by antibodies generated by the adaptive immune system.
The complement system consists of several small proteins that are synthesized in the liver and circulate in blood as inactive precursors. When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further stratification. The end result of this complement activation and a cascade of complement fixation stimulation of phagocytes to clean the outer and damaged material, inflammation, to attract additional phagocytes and activation of cell killing membrane attack complex. More than 30 proteins and protein fragments make up the complement system, including serum proteins and membrane receptors of cells. They account for about 10% of the globulin fraction of blood serum.
Three biochemical pathways activate the complement system: the classical complement pathway the alternative complement pathway and lectin path.