User:Woodis9/Antibody-dependent cellular cytotoxicity

By NK cells
The typical ADCC involves activation of NK cells by antibodies. An 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 NK cell releases cytotoxic factors that cause the death of the target cell.

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.

Furthermore, NK cells are involved in killing tumor cells and other cells that may lack MHC I on their surface, indicating a non-self cell. This is because nucleated cells of the body generally contain MHC I.

Edited
In general, ADCC has typically been described as the immune response to antibody-coated cells leading ultimately to the lysing of the infected or non-host cell. In recent literature, its importance in regards to treatment of cancerous cells and deeper insight into its deceptively complex pathways have been topics of increasing interest to medical researchers.

NK cells
The typical ADCC involves activation of NK cells by antibodies in a multi-tiered progression of immune control. An NK cell expresses Fcγ receptors. These receptors recognize and bind to the reciprocal portion of an antibody, such as IgG, which binds to the surface of a pathogen-infected target cell. The most common of these Fc receptors on the surface of an NK cell is CD16 or FcγRIII. Once the Fc receptor binds to the Fc region of the antibody, the NK cell releases cytotoxic factors that cause the death of the target cell.

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 reciprocal Fcγ 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.

Medical Applications
NK cells are involved in killing tumor cells and other cells that may lack MHC I on their surface, indicating a non-self cell. NK cells have been shown to behave similarly to memory cells due to their ability to react to destroy non-host cells only after interacting with a host cell. As NK cells are not themselves specific to certain pathways of immune control, they are utilized a majority of the time in ADCC as an less discriminate cell destroyer than antibody-specific apoptosis mechanisms.The ability of activated ex vivo NK cells has been a topic of interest for the treatment of tumors. After early clinical trials involving activation through cytokines produced poor results and severe toxicological side effects, more recent studies have produced success in regulating metastatic tumors using interleukin proteins to activate the NK cell.

ADCC as used in immune control is typically more useful for viral infections than bacterial infections due to IgG antibodies binding to virus-related antigens over prokaryotic cells. Instead of ADCC removing outside toxins, immunoglobulins neutralize products of infecting bacteria and encase infected host cells that have had bacterial toxins directly inserted through the cell membrane.

ADCC is also important in the use of vaccines, as creation of antibodies and the destruction of antigens introduced to the host body are crucial to building immunity through small exposure to viral and bacterial proteins. Examples of this include vaccines targeting repeats in toxins (RTX) that are structurally crucial to a wide variety of erythrocyte-lysing bacteria, described as hemolysins. These bacteria target the CD18 portion of leukocytes, which has historically been shown to impact ADCC in adhesion-deficient cells.