When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further cleavages. The complement system consists of a number of small proteins that are synthesized by the liver, and circulate in the blood as inactive precursors. The complement system can, however, be recruited and brought into action by antibodies generated by the adaptive immune system. It is part of the innate immune system, which is not adaptable and does not change during an individual's lifetime. The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane.
