Final answer:
The most important function of IgG antibodies is to facilitate antibody-dependent cellular cytotoxicity (ADCC), which assists in killing pathogens that are too large for phagocytosis by bringing effector cells like NK cells close to the target pathogen to secrete cytotoxins.
Step-by-step explanation:
The most important function of IgG antibodies is to facilitate antibody-dependent cellular cytotoxicity (ADCC). ADCC is a process where the Fab region of an IgG antibody binds to a large pathogen, and the Fc receptors on effector cells such as natural killer (NK) cells, macrophages, and eosinophils bind to the Fc region of the antibody. This brings the effector cells into close proximity with the target pathogen, allowing them to secrete cytotoxins like perforin and granzymes to kill the pathogen.
Phagocytosis is also an important function facilitated by IgG through a process called opsonization, which enhances the attractiveness of pathogens to phagocytic cells. Complement activation, another function of antibodies, particularly IgG and IgM, helps in recruiting and activation of the complement system, thus contributing to the inflammatory response, phagocyte attraction, and pathogen clearance.