The complement system consists of a series of plasma proteins synthesized in the liver and macrophages. The activation of this system consists in forming a protein coating, without it many bacteria would resist phagocytosis, especially... more
The complement system consists of a series of plasma proteins synthesized in the liver and macrophages. The activation of this system consists in forming a protein coating, without it many bacteria would resist phagocytosis, especially those that are covered by thick polysaccharide capsules. There are three pathways of complement activation: the classical pathway, triggered by antibodies bound to antigens; the alternative pathway, triggered by the antigens found on the microbial surfaces; and the lectin pathway, which is activated by a plasmatic protein called mannose-binding lectin which is also found in some microorganisms. The complement system is inhibited by regulatory proteins that are present in host cells and absent in microorganisms. Among the functions of complement, the following to stand out are: 1) cell lysis, 2) mediators that participate in inflammation and in the attraction of phagocytes (chemotaxis), 3) junction of microorganisms and immune complexes for their elimination through phagocytosis (opsonization). 4) increased antibody-mediated immune response (anaphylaxis).
