Which antibody is the most abundant in blood and tissue fluids?

The most abundant antibody in blood and tissue fluids is IgG. This immunoglobulin plays a crucial role in the immune response, providing long-lasting immunity by neutralizing pathogens and facilitating their destruction by other immune cells. IgG is highly effective in opsonization, a process where pathogens are marked for elimination, and it can also activate the complement system, enhancing the body's ability to fight off infections.

In addition to its prevalence, IgG has several subclasses, each providing different functions in the immune response. Its ability to cross the placenta allows for the transfer of immunity from mother to fetus, which is vital for newborn protection against infections during the early months of life. Overall, IgG’s versatility and abundant presence in the bloodstream and extracellular fluid underscore its critical importance in the adaptive immune system.