What are the barriers of innate immunity?

Options

A. Physical
B. Physiological
C. Cellular
D. All of the above

Answer

**Step-by-Step Solution:**

1. **Definition of Innate Immunity**: Innate immunity, also known as inborn immunity, is the first line of defense against pathogens and is present at birth.

2. **Physical Barriers**:
- The first barrier of innate immunity is the physical barrier.
- This includes the mucous coating of epithelial tissues that line the respiratory tract and gastrointestinal (GI) tract.
- The mucus traps pathogens and prevents them from entering the body.

3. **Physiological Barriers**:
- The second barrier is the physiological barrier.
- This includes various bodily fluids and conditions that create an unfavorable environment for pathogens.
- Examples include the acidic environment of the stomach, saliva in the mouth, and tears, which contain enzymes that can destroy pathogens.

4. **Cellular Barriers**:
- The third barrier is the cellular barrier.
- This involves various types of white blood cells that play a crucial role in innate immunity.
- Key components include polymorphonuclear leukocytes (such as neutrophils), monocytes, and natural killer (NK) cells, which can directly attack and destroy pathogens.

5. **Cytokine Barriers**:
- The fourth barrier is the cytokine barrier.
- This involves signaling proteins, particularly interferons, which are produced in response to viral infections and help to inhibit viral replication and activate immune cells.

**Summary of Barriers**:
- Physical Barrier: Mucous membranes of the respiratory and GI tracts.
- Physiological Barrier: Stomach acid, saliva, and tears.
- Cellular Barrier: Polymorphonuclear leukocytes, monocytes, and natural killer cells.
- Cytokine Barrier: Interferons.

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