Which antibody is the most abundant in the body?

IgG is the most abundant antibody in the body, making up about 70-75% of the total immunoglobulin pool in the serum. Its structure allows it to readily cross tissues and the placenta, providing passive immunity to the fetus during pregnancy. IgG plays a crucial role in the body's immune response against pathogens, particularly bacteria and viruses, by neutralizing toxins, activating complement systems, and facilitating phagocytosis through opsonization.

In contrast, IgM is primarily involved in the initial immune response and is the first antibody produced during an infection, but it is less abundant overall in circulation. IgA is found mainly in mucosal areas such as the gut, respiratory tract, and in secretions like saliva and breast milk, serving as a critical component of mucosal immunity. IgE, while important in allergic reactions and defense against parasitic infections, is present in very low concentrations compared to IgG, often associated with allergies and asthma. The predominance of IgG in the immune system highlights its pivotal role in long-term protection and memory against pathogens.