opsonins
Last reviewed 01/2018
Opsonisation (“to make tasty” - Greek) .
Opsonins are freely circulating serum molecules which are produced to attach to the surface of microbes, so rendering them more attractive to phagocytes. The process of coating a particle with opsonins is called opsonization.
Examples of opsonins include IgG antibody - part of the immune response - and the C3b molecule of the complement system. Each has receptors for both foreign particle and host phagocyte.
Opsonisation can itself stimulate the local activation of complement, further enhancing the local production of C3b opsonin and phagocytosis.
Organisms have produced a myriad of ways of circumventing opsonization, for example, Staphylococcal alpha toxin, an exotoxin, binds to the Fc region of antibody, so preventing binding of phagocyte with the opsonin.