Choose the mismatched pair from the following .

Options

A. IgG - The most abundant type of serum
B. IgG - Major antibody in secretions such as saliva , tears and breast milk
C. IgD - plays an important role in protecting against pathogens that invade through the gut or respiratory mucosa
D. IgE - Least abundant and latest isotope Which plays an important role in hypersensitivity

Answer

To determine the mismatched pair from the provided options regarding immunoglobulins (antibodies), we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding IgG**:
- IgG is mentioned as the most abundant type of antibody in serum.
- This statement is correct. IgG constitutes about 75-80% of the antibodies in the serum and is crucial for immune defense against infections.

2. **Understanding IgA**:
- The statement regarding IgA mentions that it is a major antibody present in secretions like saliva, tears, and breast milk.
- This statement is also correct. IgA is indeed the primary antibody found in mucosal areas and secretions, providing a first line of defense.

3. **Understanding IgD**:
- IgD is described as having an important role in protecting against pathogens that invade through the gut or respiratory mucosa.
- This statement is incorrect. IgD primarily functions as a receptor on B cells and is involved in the activation of B cells, rather than directly protecting against pathogens.

4. **Understanding IgE**:
- IgE is stated to be the least abundant antibody and plays a significant role in hypersensitivity reactions (such as allergies).
- This statement is correct. IgE is indeed the least abundant antibody in serum and is primarily involved in allergic responses and defense against parasitic infections.

### Conclusion:
Based on the analysis, the mismatched pair is **IgD**, as its described function does not align with its actual role in the immune system.

### Final Answer:
The mismatched pair is **IgD**.