Autoimmune diseases happen when your immune system mistakenly attacks your own body. Normally, the immune system defends against harmful invaders like bacteria and viruses. However, if it fails to distinguish between threats and your own tissues, autoimmune diseases can develop.
Autoimmunity is present to some extent in all healthy individuals. However, in healthy individuals, the immune system can suppress defective lymphocytes (immune cells) that mistakenly target the body's own cells. Autoimmunity occurs when this self-tolerance mechanism fails, leading to an immune response against the body's own tissues.
Prevalence and Types
There are over 90 types of autoimmune diseases, affecting about four million people in the UK (over 6% of the population). Some common autoimmune diseases include: