Which antibody is the most plentiful antibody in the body?

The most plentiful antibody in the body is IgG. This antibody plays a critical role in the immune response by providing the majority of antibody-based immunity against invading pathogens. It is found in all body fluids and accounts for approximately 75-80% of the total serum immunoglobulin. IgG is particularly effective because it can cross the placenta to provide passive immunity to the fetus and infant, as well as activating complement pathways and enhancing phagocytosis through opsonization.

In contrast, IgA is primarily found in mucosal areas such as the gut, respiratory tract, and in secretions like saliva and breast milk, making it vital for mucosal immunity but not the most abundant overall. IgM, while effective in the initial response to an infection, is usually present in lower concentrations after the initial stages of an immune response. IgD is found in very small amounts and is primarily involved in the activation of B cells and does not circulate in high quantities. This distinction in function and abundance highlights why IgG is recognized as the most plentiful antibody in the body.