Your immune system is a powerful defense network that protects you from harmful invaders such as bacteria and viruses (called pathogens). The immune system helps your body identify foreign substances called antigens that may harm you and launches an attack to neutralize them. You need this complex system for survival—but what happens if it doesn’t work as it should? Sometimes, your immune system may not be strong enough or prepared enough to tackle a foreign invader. You may get very sick and not recover easily. Other times, your immune system’s identification process doesn’t quite hit the mark. Autoimmunity is a condition where the immune system mistakenly targets the body’s own cells, tissues or organs, treating them as if they were harmful invaders.

Understanding the Immune System

The immune system has two main components:

• Innate immune system: As the body’s first line of defense, the innate immune system includes the skin and immune cells that attack invaders. It responds quickly to a broad range of pathogens but can’t “remember” pathogens to provide long-term immunity the next time you’re infected.
• Adaptive immune system: Unlike the innate immune system, the adaptive immune system can remember pathogens the next time they invade. B and T immune cells recognize and respond to specific antigens to give you long-term protection.

What Causes Autoimmunity?

The immune system is designed to distinguish between “self” (your body) and “nonself” (anything outside your body). It does this through specialized cells and molecules that recognize unique markers on the surface of every cell. Under normal circumstances, the immune system can distinguish between self and nonself components through a process called tolerance. When tolerance fails, B and T cells think your body is a foreign pathogen and react to it, which causes autoimmunity. Researchers are still trying to understand the exact causes of autoimmunity, but evidence so far suggests that genetic, environmental and lifestyle factors play a role. Key contributors include:

• Genetics: Certain genes can make you more susceptible to autoimmune diseases. If a close family member has an autoimmune condition, your likelihood of developing one increases. Celiac disease is an example of an autoimmune condition that tends to run in families.
• Environmental triggers: Infections, exposure to certain chemicals or even stress can sometimes act as triggers for autoimmune diseases. For example, a viral infection might confuse your immune system, leading it to attack healthy cells.
• Hormones: Autoimmune diseases are more common in women than men, suggesting that sex hormones may play a role.
• Gut Health: Your gut houses a large part of the immune system. Disruptions in the gut microbiome, the collection of microbes in the digestive system, have been linked to autoimmune conditions.

It’s also possible to develop an autoimmune disease and not be able to pinpoint any reason. There are still many unanswered questions about how autoimmunity develops.

Examples of Autoimmunity

Autoimmune diseases can affect nearly any part of the body, including the skin, joints, organs and nervous system. Some well-known examples include rheumatoid arthritis, Type 1 diabetes, lupus and multiple sclerosis. Although each autoimmune disease affects the body differently, they all share the common feature of an overactive immune response against the body itself.

Diagnosis and Treatment

Symptoms of different autoimmune diseases vary, but some common signs may include fatigue, joint pain, rashes or other skin problems, and digestive issues. Your doctor will discuss your symptoms with you if they suspect you may have an autoimmune condition. They will run blood tests that detect specific substances created by immune cells (called autoantibodies). Sometimes performing tissue biopsies can help diagnose specific autoimmune diseases too. Treatment strategies aim to reduce immune system activity and manage symptoms, and include anti-inflammatory drugs, medications that suppress the immune system and lifestyle changes.