Which antibody is primarily involved in the immune response to infections?

The antibody primarily involved in the immune response to infections is IgG. This immunoglobulin is the most abundant type of antibody found in the bloodstream and extracellular fluid, making up about 75-80% of all antibodies in the body. IgG plays a crucial role in the immune system, particularly in its ability to neutralize pathogens such as bacteria and viruses.

IgG is highly effective in opsonization, where it marks pathogens for destruction by phagocytes, and it can activate the complement system, enhancing the immune response. Furthermore, IgG is the only antibody that can cross the placenta, providing passive immunity to the fetus, which underscores its importance in defending against infections.

While IgM is also significant, particularly during the early stages of infection as the first antibody produced, IgG serves as the mainstay of long-term immunity and memory responses, which is why it is often categorized as the primary immunoglobulin involved in ongoing immune protection against infections.