Microbiology Practice Exam

Which immunoglobulin is the most abundant in the body?

1. IgM

2. IgG

3. IgA

4. IgE

The correct answer is: IgG

Immunoglobulin G, or IgG, is the most abundant antibody in the human body, constituting about 70-75% of the total immunoglobulin pool in serum. This abundance is a reflection of IgG's crucial role in the immune response. It provides long-term protection against pathogens by neutralizing toxins, opsonizing pathogens for phagocytosis, and activating the complement system, ultimately enhancing the body's ability to fight infections. IgG is particularly important in the response to infections and is the only immunoglobulin that can cross the placenta, providing passive immunity to the fetus. Its ability to persist for long periods after infection or vaccination makes it integral to both humoral immunity and immunological memory. In contrast, IgM is typically the first antibody produced in response to an infection, but it doesn't have the same longevity in circulation as IgG, resulting in it being present in lower amounts in serum. IgA plays a vital role in mucosal immunity, found predominantly in secretions like saliva, tears, and breast milk, but it is also less abundant in serum than IgG. IgE is involved mainly in allergic reactions and response to parasitic infections and is present in very low concentrations in the serum compared to Ig