complement (C) /kom″pləmənt/ [L, complementum, that which completes] , a system of at least 20 complex enzymatic serum proteins. In an antigen-antibody reaction, activation of complement causes cell lysis. Complement is also involved in other physiological reactions, including inflammation, anaphylaxis, and phagocytosis. See also antibody, antigen, antigen-antibody reaction, immune gamma globulin.
