Natural killer lymphocytes are an example for

Options

A. Physiologicaly barriers
B. Cellular barrier
C. Cytokine barriers
D. Physical barrier

Answer

**Step-by-Step Solution:**

1. **Understanding Natural Killer Cells**: Natural killer (NK) cells are a type of lymphocyte that play a crucial role in the immune system. They are known for their ability to kill virus-infected cells and tumor cells.

2. **Role in Immune Response**: NK cells are a key component of the innate immune response, which is the body’s first line of defense against pathogens. They respond quickly to infected or abnormal cells.

3. **Percentage of Circulating Lymphocytes**: NK cells make up about 5 to 20% of all circulating lymphocytes in the body, indicating their significant presence in the immune system.

4. **Mechanism of Action**: The primary function of NK cells is to provide a rapid response to virus-infected cells. They can induce cell death through mechanisms such as lysis (breaking down the cell membrane) or apoptosis (programmed cell death).

5. **Identifying the Correct Barrier**: The question asks for the type of barrier that natural killer lymphocytes represent. Given that NK cells are cells involved in the immune response, they exemplify a **cellular barrier**.

6. **Eliminating Other Options**:
- **Physiological Barrier**: This refers to barriers related to bodily functions, such as temperature and pH, which are not directly related to NK cells.
- **Cytokine Barrier**: This involves signaling molecules like interleukins and interferons, which are not the same as NK cells.
- **Physical Barrier**: This includes structures like skin and mucous membranes that physically block pathogens, which again is not applicable to NK cells.

7. **Conclusion**: Therefore, the correct answer is that natural killer lymphocytes are an example of a **cellular barrier**.

**Final Answer**: Natural killer lymphocytes are an example of **cellular barrier**.

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