Question

Which antibody class is most abundant in human serum?

• A. IgA
• B. IgD
• C. IgE
• D. IgG

Hint:

Remember the order of abundance in serum using the acronym: {GAMED} (IgG > IgA > IgM > IgD > IgE).

Answer 1

The Correct Option is D

The question asks which antibody class is most abundant in human serum. To answer this question accurately, we need to understand the different classes of antibodies (Immunoglobulins) and their roles in the human immune system.

There are five main classes of antibodies:

1. IgG (Immunoglobulin G): This is the most abundant class of antibodies in human serum. It constitutes about 75-80% of all antibodies. IgG is critical for long-term protection because it helps in combating bacterial and viral infections. It can cross the placenta and provide passive immunity to the fetus.
2. IgA (Immunoglobulin A): IgA is found in mucous membranes, particularly in the respiratory and gastrointestinal tracts. It is also present in tears, saliva, and breast milk. IgA plays a crucial role in mucosal immunity but is not the most abundant in serum.
3. IgM (Immunoglobulin M): This is the first antibody produced in response to an infection and is primarily found in blood and lymphatic fluid. Although it is the largest antibody, it is not the most abundant in terms of concentration in serum.
4. IgD (Immunoglobulin D): IgD is present in small amounts in the blood serum. Its primary function is still under study, but it is thought to play a role in the initiation of immune responses.
5. IgE (Immunoglobulin E): IgE is associated mainly with allergic reactions and is found in very low concentrations in the serum.

From the descriptions above, it is clear that IgG is the most abundant antibody class in human serum.

By understanding these functions and concentrations, we conclude that the correct answer is IgG.

Answer 2

Step 1: Understanding the Concept:
In humans, there are five classes of immunoglobulins (antibodies): IgA, IgD, IgE, IgG, and IgM. They differ in their biological properties, locations, and concentrations.
Step 2: Detailed Explanation:
IgG is the most prevalent antibody class in the blood and tissue fluids, making up about \(75-80%\) of the total serum antibodies.
It is highly significant because it can cross the placenta to provide passive immunity to the fetus.
- IgA (Option A) is the most abundant antibody in secretions (breast milk, saliva, mucus).
- IgM is the first antibody produced during an initial immune response.
- IgE (Option C) is involved in allergic reactions.
Step 3: Final Answer:
IgG is the antibody class that exists in the highest concentration in human serum.