Antibody-dependent cell-mediated cytotoxicity

The antibody-dependent cell-mediated cytotoxicity (ADCC) is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system actively lyses a target cell, whose membrane-surface antigens have been bound by specific antibodies. In humans, ADCC is usually mediated by IgG. It is one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection.

Classical antibody-dependent cell-mediated cytotoxicity is mediated by natural killer (NK) cells; but macrophages, neutrophils and eosinophils can also mediate it. For example, eosinophils can kill certain parasitic worms known as helminths through ADCC mediated by IgE.

ADCC is part of the adaptive immune response due to its dependence on a prior antibody response.

The typical ADCC involves activation of NK cells by antibodies. A NK cell expresses Fc receptors, mostly CD16. These receptors recognize, and bind to, the Fc portion of an antibody, such as IgG, which has bound to the surface of a pathogen-infected target cell. The most common Fc receptor on the surface of an NK cell is called CD16 or FcγRIII. Once the Fc receptor binds to the Fc region of IgG, the Natural Killer cell releases cytokines such as IFN-γ

During replication of a virus some of the viral proteins are expressed on the cell surface membrane of the infected cell. Antibodies can then bind to these viral proteins. Next, the NK cells which have Fc Receptors will bind to that antibody, inducing the NK cell to release proteins such as perforin and proteases known as granzymes, which causes the lysis of the infected cell to hinder the spread of the virus.

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