Opsonins

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Opsonins are proteins found in the body that are part of the immune response . Opsonins can be either antibodies or complement factors that facilitate the linkage of phagocytes to bacterial cells or other microorganisms by acting as a bridge between the two cells. In this context, one speaks of the opsonization of the target cell. To a certain extent, phagocytes can bind directly to bacteria or other cells with an antigenic character. However, the binding is strengthened by an activated complement factor - a plasma protein that represents the humoral part of the unspecific immune response - in that the complement factor acts as a bridge between the bacterium and the corresponding complement receptor of the phagocyte.

In organisms that can only activate small amounts of complement factors, opsonization is alternatively or additionally carried out with antibodies. The binding principle is similar here: the antibody is linked via its Fc fragment to the Fc receptor of the phagocyte and via its Fab fragments to the corresponding epitope of the antigenic microorganism. The opsonization ultimately secures the phagocytosis of the bound organism and cell lysis can be initiated.

literature

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