Autoimmune disease occurs because of autoimmunity -- an unnatural condition where the immune response, which normally protects the body from foreign invaders and substances backfires and attacks normal tissues. Antibodies and white cells are directed against parts of the body, causing inflammation and injury to certain tissues and organs. The triggers are usually unknown. There are over 40 such diseases including juvenile diabetes, multiple sclerosis, rheumatoid arthritis, myasthenia gravis and lupus.
The immune system is the body's defense against invaders. Like an internal army, it has to clearly distinguish friend from foe—to know itself from others. Autoimmunity occurs when the immune system gets confused and healthy tissues get caught in friendly cross-fire. In fighting something—an infection, a toxin, an allergen, a food or the stress response—the immune system somehow it redirects its hostile attack on joints, brain, thyroid, gut, skin, or sometimes the whole body.
Every person has some degree of autoimmunity naturally and it does not seem to do any harm. It is only a minority of cases where autoimmunity actually produces damage in the body, producing disease. At their root of autoimmune conditions is one central biochemical process: a runaway immune response also known as systemic inflammation that results in the body attacking its own tissues.
Loss of immune tolerance generally does not happen overnight. It is a process that takes months or years of stress to the immune system. Prior to the development of an autoimmune disorder or a disease, there is a period of “silent autoimmunity”. Silent autoimmunity is the time before the body's immune system reaches the breaking point of full-blown disease presentation and pathological tissue damage, but small amounts of antibodies are being formed.
Genetics is involved in the development of autoimmune disease, but autoimmune diseases are not typical genetic diseases. Within families that are susceptible to autoimmunity, one family member may have lupus, another family member may have Sjogren's disease, a third member of the family may have rheumatoid arthritis.
Environmental factors account for around half of autoimmunity susceptibility. Few of the environmental triggers are known. Certain drugs can induce lupus. Certain environmental substances like silica that can induce scleroderma. It is suspected that there are certain dietary substances, such as iodine, that can exacerbate thyroid disease.
Autoimmune disorders occur almost exclusively in developed countries. People in poor nations without modern amenities like running water, flush toilets, washing machines, and sterile backyards don’t usually get these diseases; neither do those who grew up on a farm with lots of animals.. It is posited that playing in the dirt, being dirty, and being exposed to bugs and infections trains your immune system to recognize what is foreign and what is “you.”
In the USA, autoimmune diseases, when taken all together, are a huge health burden affecting an estimated 24 million people in 2016. They are the eighth leading cause of death among women, shortening the average patient’s lifespan by eight years. The annual health care cost for autoimmune diseases is $120 billion a year representing nearly twice the economic health care burden of cancer (about $70 billion a year).