Membrane bound antibodies are present on surface of

Options

A. Mature B-cells
B. Mature T-cells
C. Memory cells
D. Both 1 and 3

Answer

### Step-by-Step Solution

1. **Understanding the Question**: The question asks about the presence of membrane-bound antibodies on the surface of certain immune cells.

2. **Identifying Immune Cells**: The primary immune cells involved in the question are B cells and T cells. B cells are responsible for producing antibodies, while T cells play a role in cell-mediated immunity.

3. **Membrane-Bound Antibodies**: Membrane-bound antibodies are specifically associated with B cells. These antibodies are integral to the B cell's function of recognizing antigens (pathogens).

4. **Types of Immune Cells**:
- **Mature B Cells**: These cells have membrane-bound antibodies on their surface, which allows them to recognize specific antigens.
- **Mature T Cells**: These cells do not have membrane-bound antibodies; instead, they have T-cell receptors (TCRs) that recognize antigens presented by other cells.
- **Memory Cells**: These can refer to both memory B cells and memory T cells. Memory B cells have membrane-bound antibodies, while memory T cells do not.

5. **Conclusion**: The correct answer to the question is that membrane-bound antibodies are present on the surface of mature B cells and memory B cells. Therefore, the correct option is both 1 (Mature B Cells) and 3 (Memory Cells).

### Final Answer
Membrane-bound antibodies are present on the surface of:
- Mature B Cells (Option 1)
- Memory Cells (Option 3)
Thus, the correct answer is both 1 and 3.

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