Final answer:
Neutrophils and macrophages have Fc receptors that bind to the constant regions of IgG heavy chains. This process is part of the immune response known as opsonization, where antibodies act as opsonins to mark pathogens for destruction by phagocytic cells.
Step-by-step explanation:
Neutrophils and macrophages have cell surface receptors that bind to constant regions of IgG heavy chains. These receptors are known as Fc receptors, and they recognize the Fc region of antibodies, particularly of the IgG class. The IgG antibodies, which compose about 80% of all antibodies, have heavy chains with one variable domain and three identical constant domains. The constant regions are the same for all antibodies in a given class, and these regions determine the antibody's class and its immune functions.
When antibodies bind to pathogens, they act as opsonins, marking the pathogens for destruction by phagocytic cells like neutrophils and macrophages. This process is known as opsonization. The presence of antibodies on a pathogen enhances the phagocytic action of cells like macrophages, which use their Fc receptors to bind to the constant regions of the opsonized antibodies, facilitating the phagocytosis and elimination of the pathogen.