ADCC

Antibody-Dependent Cellular Cytotoxicity (ADCC) and Natural Killer (NK) Cells

• NK cells bind to antibody-coated cells and destroy them through a process called ADCC.
• FcγRIII (CD16) is an activating receptor on NK cells that binds to IgG antibodies and triggers the destruction of antibody-coated cells.
• ADCC is involved in the destruction of cells infected with enveloped viruses and is a mechanism of action for therapeutic antibodies used in cancer treatment.
• Immunoglobulin E– and Eosinophil/Mast Cell– Mediated Reactions are also related to ADCC.

The Complement System

• The complement system consists of proteins that aid in host defense against microbes and tissue injury.
• It can be activated by microbes in the absence of antibodies as part of the innate immune response, or by antibodies as part of adaptive immunity.
• The complement system's activation involves proteolytic cleavage of proteins, leading to the generation of effector molecules that help eliminate microbes.
• Deficiencies in complement proteins can result in immune deficiencies, increased susceptibility to infections, and autoimmune diseases.

Complement System Functions

• The complement system not only has antimicrobial functions but also stimulates B cell responses and antibody production.
• Complement proteins bound to antigen-antibody complexes are recognized by follicular dendritic cells in germinal centers, promoting antibody production.
• Antibodies have protective functions at mucosal organs and the fetus, in addition to their role in peripheral lymphoid organs and the bloodstream.