What is the primary function of the FAB region in an antibody?

The primary function of the FAB region in an antibody is to bind to antigens. The FAB region, which stands for fragment antigen-binding, consists of the variable regions of the heavy and light chains of the antibody. This region is specifically designed to recognize and bind to unique epitopes on antigens, which can be proteins, carbohydrates, or other molecules. The binding of the FAB region to an antigen is crucial for the immune response, as it allows antibodies to tag pathogens for destruction, neutralize toxins, or facilitate other immune mechanisms.

The ability of the FAB region to selectively bind to antigens is due to its unique structure and variability among different antibodies, allowing for a diverse range of specificities tailored to different pathogens. This specificity is a key feature of the adaptive immune system, enabling the body to respond effectively to various infections.