In higher vertebrates, the immune system can distinguish self-cells and non-self. If this property is lost due to genetic abnormality and it attacks self-cells, then it leads to:
As we learnt
Auto-immune disease -
Sometimes, due to genetic and other unknown reasons, the body attack self-cells. This results in damage to the body and is called auto-immune disease.
Rheumatoid arthritis which affects many people in our society is an auto-immune disease.
When the immune system cannot differentiate between self and non-self cells then the immune system attacks and destroys the self-cells and this is called auto-immunity.