Which of the following is the major immunoglobulin in human serum, accounting for 80% of the immunoglobulin pool?

Options

A. IgM
B. IgD
C. IgE
D. IgG

Answer

**Step-by-Step Solution:**

1. **Understanding Immunoglobulins**: Immunoglobulins, also known as antibodies, are proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses. There are five main classes of immunoglobulins in humans: IgA, IgD, IgE, IgG, and IgM.

2. **Identifying the Major Immunoglobulin**: Among these classes, we need to determine which one is the most abundant in human serum.

3. **Analyzing Each Immunoglobulin Class**:
- **IgA**: This immunoglobulin is primarily found in mucosal areas, such as the gut and respiratory tract, and accounts for about 10-15% of the total immunoglobulin pool.
- **IgD**: This class is present in very low amounts, less than 1% of the total immunoglobulin pool.
- **IgE**: This immunoglobulin is involved in allergic reactions and is also found in very low concentrations in serum.
- **IgM**: This is the first antibody produced in response to an infection and accounts for about 5-10% of the total immunoglobulin pool.
- **IgG**: This is the most abundant immunoglobulin in human serum, accounting for approximately 70-80% of the total immunoglobulin pool.

4. **Conclusion**: Based on the analysis, the major immunoglobulin in human serum, which accounts for 80% of the immunoglobulin pool, is **Immunoglobulin G (IgG)**.

**Final Answer**: Immunoglobulin G (IgG)

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