Name the cells that release pyrogens. What is the role of these substances in the defence of the body?

Explanation

### Step-by-Step Solution:

1. **Identify the Cells that Release Pyrogens:**
- Pyrogens are fever-producing substances that are primarily released by certain microorganisms, such as bacteria and yeast. The specific cells that release pyrogens include:
- **Bacteria:** They release pyrogens through their cell walls, which contain components like lipopolysaccharides.
- **Yeast:** Similar to bacteria, yeast can also produce pyrogens.

2. **Understand the Nature of Pyrogens:**
...