How many major classes of antibodies are found?

Options

A. four
B. five
C. three
D. seven

Answer

To answer the question "How many major classes of antibodies are found?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Antibodies**: Antibodies, also known as immunoglobulins, are glycoproteins produced by plasma cells. They play a crucial role in the immune response by neutralizing antigens.

2. **Identifying Major Classes**: There are five major classes of antibodies, which are categorized based on their structure and function.

3. **Listing the Classes**: The five major classes of antibodies are:
- **IgM (Immunoglobulin M)**: The first antibody produced in response to an infection.
- **IgD (Immunoglobulin D)**: Functions mainly as a receptor on B cells that have not been exposed to antigens.
- **IgA (Immunoglobulin A)**: Found in mucosal areas, such as the gut, respiratory tract, and urogenital tract, and in secretions like saliva and tears.
- **IgE (Immunoglobulin E)**: Involved in allergic reactions and responses to parasitic infections.
- **IgG (Immunoglobulin G)**: The most abundant antibody in circulation, capable of crossing the placenta to provide immunity to the fetus.

4. **Conclusion**: Therefore, the total number of major classes of antibodies is **5**.

### Final Answer:
The number of major classes of antibodies found is **5**.

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