Autoimmune diseases are medical conditions in which the immune system attacks the body’s own cells and tissues instead of foreign materials and invasive pathogens (disease-causing agents). More than 80 conditions are known or potential autoimmune diseases.

Together, these diseases afflict between 14 and 24 million Americans, according to the National Institutes of Health. Autoimmune disorders may affect between 5 and 8 percent of the U.S. population, according to the Centers for Disease Control and Prevention. However, these conditions appear to be occurring more frequently than in past decades.

The immune system uses antibodies to fight infections. Antibodies are proteins that recognize pathogens such as viruses and bacteria and prevent the invasion and unwanted production of cells. They also help rid the body of toxins and malignant (cancerous) cells. When an unfamiliar antigen (foreign body) enters the body, white blood cells produce antibodies designed specifically to attack it. Other white blood cells known as T cells (T lymphocytes), along with a group of chemicals known as the complement system, work with the antibodies to eliminate the foreign organism.

The immune system also develops the ability to distinguish between the body’s own cells and proteins, and those of antigens. When this normal process is disrupted, the immune system may attack the body’s cells. This process is the basis of autoimmune disease development in humans.