Immunoglobulin found in serum (of new born) is

Options

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

Answer

To answer the question regarding which immunoglobulin is found in the serum of a newborn, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Immunoglobulins**: Immunoglobulins, or antibodies, are proteins produced by the immune system to identify and neutralize pathogens like bacteria and viruses. There are several types of immunoglobulins, each with distinct functions.

2. **Identifying the Types**: The main types of immunoglobulins include:
- **IgG (Immunoglobulin G)**: The most common antibody in the blood, making up about 75% of serum antibodies.
- **IgA (Immunoglobulin A)**: Primarily found in mucous membranes and secretions like saliva and tears.
- **IgM (Immunoglobulin M)**: The first antibody produced in response to an infection and the largest antibody.
- **IgE and IgD**: Less common and involved in allergic reactions and other specific immune responses.

3. **Focus on Newborns**: Newborns receive antibodies from their mothers, primarily through the placenta during pregnancy. This transfer is crucial for providing the newborn with passive immunity.

4. **Key Point about IgG**: Among the immunoglobulins, IgG is the only type that can cross the placental barrier. Therefore, the primary immunoglobulin found in the serum of newborns is maternal IgG.

5. **Conclusion**: Based on the information, the immunoglobulin found in the serum of a newborn is **Immunoglobulin G (IgG)**.

### Final Answer:
The immunoglobulin found in serum (of newborn) is **Immunoglobulin G (IgG)**.

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