All of the following cells are examples of cellular barriers , except

Options

A. Natural killer cells (NK cells)
B. Macrophages
C. Lymphocytes
D. Neutrophils

Answer

To solve the question, "All of the following cells are examples of cellular barriers, except?", we need to analyze each of the given options and determine which cell does not function as a cellular barrier.

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a cell that is NOT an example of a cellular barrier. Cellular barriers are typically involved in the immune response and help protect the body from pathogens.

2. **Evaluate the First Option - Natural Killer Cells**:
- Natural Killer (NK) cells are part of the innate immune system.
- They play a crucial role in controlling tumors and microbial infections.
- **Conclusion**: NK cells are indeed a type of cellular barrier.

3. **Evaluate the Second Option - Macrophages**:
- Macrophages are specialized immune cells that detect, engulf, and destroy pathogens through a process called phagocytosis.
- They are essential for the immune defense and act as a barrier to infections.
- **Conclusion**: Macrophages are also a type of cellular barrier.

4. **Evaluate the Third Option - Lymphocytes**:
- Lymphocytes are primarily involved in the adaptive immune response.
- They include T cells and B cells, which are crucial for specific immune responses but do not act as physical barriers.
- **Conclusion**: Lymphocytes do not function as cellular barriers in the same way that NK cells and macrophages do.

5. **Evaluate the Fourth Option - Neutrophils**:
- Neutrophils are a type of white blood cell that plays a key role in the immune response, particularly in phagocytosis.
- They are one of the first responders to sites of infection and act as a cellular barrier against pathogens.
- **Conclusion**: Neutrophils are also a type of cellular barrier.

6. **Final Decision**: Based on the evaluations, the only cell that does not function as a cellular barrier is **Lymphocytes**. Therefore, the correct answer is option 3.

### Final Answer:
**Option 3: Lymphocytes** are not an example of a cellular barrier.