Functions of antibodies/ Antibody functions
Antibody Functions and Mechanisms
Overview of Antibody Structure
- Antibodies consist of two main parts: the Fragment Antigen Binding (Fab) fragment, which recognizes and binds to antigens, and the Fragment Crystallizable (Fc) region, which interacts with immune cell receptors to trigger effector functions for antigen destruction.
Key Functions of Antibodies
Opsonization
- Opsonization is a process where antibodies bind to pathogens, marking them for phagocytosis by immune cells. This enhances the ability of phagocytes to identify and eliminate pathogens.
Neutralization
- Neutralizing antibodies can attach to viruses or other pathogens, blocking their entry into host cells by binding to specific receptors on their surface, thus preventing infection.
Complement Activation
- The complement system involves plasma proteins that work together against infections. When a complement protein detects antibodies on a pathogen's surface, it activates other complement proteins leading to the formation of the membrane attack complex that punctures the pathogen's membrane.
Immune Complex Formation
- Multiple antigens and antibodies can form immune complexes that limit antigen mobility. This facilitates easier phagocytosis and allows simultaneous destruction of several pathogens by clustering them together.
Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)
- In ADCC, antibodies bind to infected or tumor cells. Natural killer (NK) cells recognize the Fc portion of these antibodies and release cytotoxic granules like perforin and granzymes that induce apoptosis in target cells.