Antigenbindungsdomäne

Antigenbindungsdomäne is a region of an antibody molecule that specifically recognizes and binds to an antigen. This crucial part of the antibody is responsible for the specificity of the immune response, ensuring that antibodies target foreign invaders like bacteria and viruses while leaving the body's own cells unharmed. Each antibody molecule has two identical antigen-binding sites, located at the tips of the Y-shaped structure.

The antigen-binding domain, also known as the Fab fragment (for fragment antigen-binding), is composed of both the variable regions of the antibody's heavy and light chains. Within these variable regions are three hypervariable loops, also called complementarity-determining regions (CDRs). These CDRs form the three-dimensional structure of the antigen-binding site and are highly diverse, allowing them to interact with a vast array of different antigen shapes and chemical properties. The precise arrangement of amino acids in the CDRs dictates which specific antigen the antibody can bind to. This lock-and-key mechanism is fundamental to adaptive immunity.