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

Higher vertebrates can tell the difference between foreign molecules and foreign organisms. The majority of experimental immunology is concerned with this feature. But the immune system can sometimes fail to distinguish between foreign particles (non-self cells) and self cells for unclear causes and starts attacking and destroying healthy body tissue by mistake. This results in damage to the body and is called auto-immune disease.