The type of immunoglobulin whose function is possible antigen recognition by B-cells may be:

Options

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

Answer

To solve the question regarding the type of immunoglobulin responsible for antigen recognition by B-cells, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Immunoglobulins**: Immunoglobulins, also known as antibodies, are proteins produced by B-cells that play a crucial role in the immune response by recognizing and binding to specific antigens.

2. **Identify the Types of Immunoglobulins**: There are five main classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM. Each has distinct functions in the immune system.

3. **Analyze Each Option**:
- **IgA**: Primarily found in mucosal areas, such as saliva, tears, and blood, and protects against pathogens. It does not primarily function in antigen recognition by B-cells.
- **IgD**: This immunoglobulin is found on the surface of B-cells and plays a key role in the activation of B-cells by recognizing antigens.
- **IgE**: Involved in allergic reactions and protection against parasitic infections, but not primarily in antigen recognition by B-cells.
- **IgG**: The most abundant antibody in the blood and extracellular fluid, it provides the majority of antibody-based immunity against invading pathogens but is not specifically for B-cell activation.

4. **Determine the Correct Answer**: From the analysis, IgD is specifically involved in recognizing antigens and signaling B-cells for activation. Therefore, the correct answer is **IgD**.

### Final Answer:
The type of immunoglobulin whose function is possible antigen recognition by B-cells is **IgD**.

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