Step 1: Overview of immunoglobulins.
Humans produce five major classes of antibodies—IgA, IgD, IgE, IgG, and IgM. Each class differs in function, distribution within the body, and relative abundance.
Step 2: Comparing antibody concentrations.
Among all immunoglobulins, IgG is present in the greatest amount in blood plasma and extracellular fluid, accounting for nearly 75–80% of total serum antibodies.
IgG plays a vital role in long-term immunity and is the only antibody class that can cross the placenta, thereby providing passive immunity to the developing fetus.
Other classes include:
• IgA – predominantly found in secretions such as saliva, tears, and breast milk.
• IgM – produced first during an initial immune response.
• IgE – associated mainly with allergic reactions and hypersensitivity.
Step 3: Final conclusion.
The antibody present in the highest concentration in human serum is IgG.