Lipopolysaccharides of gram-negative bacteria acts as endotoxin and has pyrogen effect for human. Few nanograms of pyrogen can cause very high fever. This stimulates macrophages and neutrophils to secrete `IL-1 beta, TNF -alpha and IL-6` that act on the hypothalamus to produce fever. Fever forms ...... barrier of innate immunity :-

Options

A. Physiological
B. Physical
C. Cellular
D. Cytokine

Answer

To solve the question, we need to analyze the role of lipopolysaccharides (LPS) from gram-negative bacteria and how they affect the immune response, particularly in relation to fever and innate immunity.

### Step-by-Step Solution:

1. **Understanding Lipopolysaccharides (LPS)**:
- LPS are components of the outer membrane of gram-negative bacteria.
- They act as endotoxins, meaning they can trigger a strong immune response in humans.

**Hint**: Remember that LPS are not just structural components; they play a significant role in immune system activation.

2. **Effect of LPS as Pyrogens**:
- When LPS enters the human body, it has a pyrogenic effect, meaning it can induce fever.
- Even small amounts (nanograms) of pyrogens can cause a significant increase in body temperature.

**Hint**: Pyrogens are substances that cause fever; think about how the body responds to infection.

3. **Immune Response Activation**:
- The presence of LPS stimulates immune cells like macrophages and neutrophils.
- These cells secrete cytokines such as IL-1 beta, TNF-alpha, and IL-6.

**Hint**: Cytokines are signaling molecules that mediate and regulate immunity and inflammation.

4. **Action on the Hypothalamus**:
- The cytokines act on the hypothalamus, which is the brain region that regulates body temperature.
- This leads to an increase in body temperature, resulting in fever.

**Hint**: The hypothalamus is crucial for maintaining homeostasis, including temperature regulation.

5. **Fever as a Barrier of Innate Immunity**:
- Fever acts as a physiological barrier of innate immunity.
- The elevated body temperature can inhibit the growth of pathogens, making it harder for them to survive and multiply.

**Hint**: Consider how physiological responses like fever can enhance the body's defense mechanisms.

6. **Identifying the Correct Answer**:
- The question asks what type of barrier fever forms in innate immunity.
- The options are physiological, physical, cellular, and cytokines.
- Since fever is a physiological response that helps fight infection, the correct answer is **physiological barrier**.

**Hint**: Think about the different types of barriers in the immune system: physiological responses are part of the innate immune defense.

### Final Answer:
Fever forms a **physiological barrier** of innate immunity.