What is meant by auto-immune diseases? Give two example.

Explanation

### Step-by-Step Solution:

1. **Definition of Autoimmune Diseases**:
Autoimmune diseases are disorders that occur when the immune system mistakenly attacks and destroys the body's own cells. Normally, the immune system protects the body from infections and pathogens, but in autoimmune diseases, it fails to distinguish between foreign invaders and the body’s own healthy cells.

2. **Mechanism of Autoimmune Diseases**:
In autoimmune diseases, the body’s immune cells, which are meant to protect the body, start to identify its own cells as harmful. This leads to an immune response that results in the destruction of these healthy cells. The affected body cells act as self-antigens, triggering an inappropriate immune response.

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