Which immunoglobulin class is known for being the most abundant in serum?

• A. IgA
• B. IgG
• C. IgM
• D. IgE

Answer: (B)

IgG is identified as the most abundant immunoglobulin class in serum, accounting for approximately 75-80% of the total immunoglobulin pool in the bloodstream. This high concentration makes IgG particularly significant in the immune response, as it plays a crucial role in identifying and neutralizing pathogens such as bacteria and viruses.

In addition to its prevalence, IgG is known for its ability to cross the placenta, providing passive immunity to the fetus, which highlights its functional importance in both maternal and neonatal health. Furthermore, IgG has several subclasses that contribute to its diverse functions, including the ability to activate complement pathways, opsonization (facilitating phagocytosis), and neutralizing toxins and viruses. These characteristics solidify IgG's position as the predominant immunoglobulin in the serum, crucial for long-term immunity and protection against infections.