What is the main function of the Fab region of an immunoglobulin molecule?

The main function of the Fab region of an immunoglobulin molecule is to bind to antigens. The Fab, or fragment antigen-binding, region consists of the variable domains of the heavy and light chains that form a unique structure tailored to recognize specific antigens. This binding is crucial in the immune response, allowing antibodies to identify and neutralize foreign pathogens or mark them for destruction by other components of the immune system.

The antigen-binding capability of the Fab region is critical for initiating various immune processes, such as neutralization of toxins or pathogens, and promoting phagocytosis by marking antigens for recognition by immune cells. While the other options describe important functions of immunoglobulins, they are not directly attributed to the Fab region but may involve other parts of the antibody molecule or different mechanisms in the immune response.