The immunoglobulin abundant in colostrum is

Options

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

Explanation

**Step-by-Step Solution:**

1. **Understanding Colostrum**: Colostrum is the first form of milk produced by mammals immediately following the delivery of the newborn. It is rich in antibodies and nutrients essential for the newborn's immune system.

2. **Identifying Immunoglobulins**: There are several types of immunoglobulins (antibodies) in the human body, including IgG, IgM, IgD, and IgA. Each type has a specific role in the immune response.

3. **Analyzing Each Immunoglobulin**:
- **IgG**: This is the most abundant antibody in the bloodstream and is known for providing passive immunity to the fetus by crossing the placenta. However, it is not the primary immunoglobulin found in colostrum.
- **IgM**: This antibody is primarily involved in the early stages of immune response and is found on the surface of B cells. It is not the predominant immunoglobulin in colostrum.
- **IgD**: This immunoglobulin functions mainly as a receptor on B cells and is not found in significant amounts in colostrum.
- **IgA**: This antibody is crucial for mucosal immunity and is found in high concentrations in secretions such as saliva, tears, and importantly, colostrum.

4. **Conclusion**: Based on the analysis, the immunoglobulin that is abundant in colostrum is **IgA**. Specifically, it is present in the form of secretory IgA, which plays a vital role in protecting the mucosal surfaces of the newborn.

5. **Final Answer**: The immunoglobulin abundant in colostrum is **IgA**.

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