The body’s immune system is necessary for fending off illness. But for the 5 percent of people with autoimmune diseases, this natural defense system turns on itself and attacks body cells as if they were dangerous foreign invaders. There are more than 80 types of these diseases, including rheumatoid arthritis, multiple sclerosis, and lupus. Women are twice as likely to be affected as men are.

Normally, the immune system’s attack cells—white blood cells called lymphocytes (B and T cells)—recognize the body’s major histocompatibility complex (MCH), a type of personal bar code that every cell contains. But a genetic defect, virus, or induced mutation can produce faulty versions of these cells that ignore this safety feature and instead home in on some of the body’s own cells. The body may also grow new cells with different MCHs that the immune system doesn’t recognize.

There are two types of autoimmune diseases. One is organ specific, in which the immune system targets antigens in one particular organ. (An example of this is type 1 diabetes, which attacks the insulin-producing cells in the pancreas.) The more common type is systemic, in which several organs or the connective tissues are affected. Symptoms of autoimmune diseases vary, but early signs often include fatigue, muscle aches, and low fever; cycles of flare-ups and remission are common. Treatments depend on the specific disease, but drugs that relieve the inflammatory response are frequently prescribed.

ADDITIONAL FACTS

  1. The autoimmune disease lupus is named after the Latin word for “wolf” because of its skin rash and lesions that resemble wolf bites.
  2. The holy grail of treating autoimmune disease is being able to suppress the harmful immune mechanisms without affecting the entire system. For example, some multiple sclerosis patients may benefit from injections of antibodies that neutralize the overactive B and T cells.
  3. Autoimmune diseases often run in families.