What is an auto immune disease?

Autoimmune disease :

1. WBCs produce antibodies.
2. These antibodies attack and kill bacteria, viruses, and other parasites.
3. The antibodies target the foreign cells and attack them without causing any harm to the host tissues.
4. But, in some humans, the lymphocytes produce some antibodies called autoantibodies.
5. They run in the blood and damage the healthy tissues of the human.
6. This results in some disorder in the functioning of the system of that human body.
7. These are called autoimmune diseases.
8. Examples: vitiligo, rheumatic fever, rheumatoid arthritis, etc.