Which of the following immunoglobulin (Ig) is present in colostrum?

Options

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

Explanation

To determine which immunoglobulin (Ig) is present in colostrum, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Immunoglobulins**:
- Immunoglobulins are antibodies that play various roles in the immune response. They are classified into different types (IgA, IgG, IgM, IgE) based on their structure and function.

2. **Identify the Types of Immunoglobulins**:
- **IgA**: Primarily found in mucosal areas, such as the gut, respiratory tract, and urogenital tract, and is also present in secretions like saliva, tears, and breast milk.
- **IgG**: The most abundant antibody in the blood and extracellular fluid, it is the only antibody that can cross the placenta to provide immunity to the fetus.
- **IgM**: The first antibody produced in response to an infection; it is mainly found in the blood and lymphatic fluid.
- **IgE**: Involved in allergic reactions and responses to parasitic infections.

3. **Focus on Colostrum**:
- Colostrum is the first form of milk produced by mammals immediately following delivery. It is rich in antibodies and provides essential nutrients and immune protection to the newborn.

4. **Determine the Immunoglobulin Present in Colostrum**:
- Among the options given (IgA, IgG, IgM, IgE), IgA is known to be present in high concentrations in colostrum. It plays a crucial role in mucosal immunity and helps protect the newborn's intestines from infections.

5. **Conclusion**:
- Therefore, the immunoglobulin present in colostrum is **IgA**.

### Final Answer:
The immunoglobulin present in colostrum is **IgA**.