Final answer:
IgG is the main antibody of secondary immune responses, while IgM is the first antibody produced during primary and secondary immune responses. IgG clears pathogens from the blood and can activate complement proteins, while IgM serves as an important diagnostic marker during active or recent infections.
Step-by-step explanation:
IgG and IgM are both types of antibodies produced by the immune system in response to an infection or vaccination. IgG is the main antibody of secondary immune responses, meaning it is produced after initial exposure to a pathogen. It is a monomeric antibody that clears pathogens from the blood and can activate complement proteins, which help to destroy pathogens.
IgM, on the other hand, is the first antibody produced during primary and secondary immune responses. It is initially produced in a membrane-bound form and then secreted as a pentamer with five monomers bound together. Although IgM does not bind to antigens as stably as IgG, it plays an important role in the body's defense against infections.