Final answer:
IgG-mediated opsonization is a process in which IgG antibodies coat bacteria to promote phagocytosis by phagocytic cells, which have Fc receptors that recognize the coated pathogens. This coating not only promotes rapid clearance of pathogens but also neutralizes them and activates the complement system.
Step-by-step explanation:
Understanding IgG-Mediated Opsonization
IgG antibodies serve an important role in the immune system's defense by coating bacteria to promote phagocytosis. This process, called opsonization, enhances the ability of phagocytic cells like macrophages, dendritic cells, and neutrophils to attach to and engulf pathogens. These cells use Fc receptors to bind the Fc portion of IgG-opsonized pathogens, which marks them for destruction.
The coated pathogens can be neutralized, preventing them from infecting host cells. Furthermore, in a process known as complement fixation, IgG binds to antigens on the surface of pathogens, which along with complement proteins, enhances opsonization, thereby promoting rapid clearance of pathogens.
IgG antibodies also participate in other immune responses, such as neutralization of pathogens, agglutination of bacteria, and activation of the complement cascade, which includes the formation of the membrane attack complex (MAC) to kill gram-negative bacterial pathogens.