The immune system is designed to defend the body against invading foreign or dangerous substances. A healthy immune response consists of recognizing a foreign substance and attacking it. Disorders of the immune system occur when the body generates an immune response against itself (autoimmune disorders), when the body cannot generate an appropriate response against invading microorganisms (immunodeficiency disorders), or when the body generates an exaggerated immune response or reaction to substances that are generally not harmful (allergic reactions).

Show Full Description The body's first line of defense against invaders is mechanical, or physical barriers, such as the skin and the membranes that line the respiratory, digestive, urinary, and reproductive tracts. The next line of defense involves white blood cells traveling through the bloodstream that recognize and attack invading cells. Together, these components comprise part of the immune system. With a healthy patient, the body distinguishes its own cells from foreign cells and reacts only against foreign substances called antigens. In patients with immune disorders, the normal immune response goes awry. Autoimmune disorders cause the body to interpret its own tissue as foreign, causing the immune system to attack the patient's own body. Different cells or tissues are targeted in different autoimmune disorders. Examples of autoimmune disorders are lupus, multiple sclerosis, and rheumatoid arthritis. Autoimmune disorders commonly cause fever, fatigue and various other symptoms depending on which body tissues are being attacked. Blood tests can help identify autoimmune disorders. Unfortunately, most autoimmune disorders are usually lifelong and cannot be cured. Symptoms may be managed by controlling the autoimmune reaction through suppressing the immune system. Immunodeficiency disorders impair the immune system's ability to defend the body against foreign or abnormal cells. An immunodeficiency disorder may be present at birth (congenital) or may develop later in life, often as a result of another disorder (acquired). People with immunodeficiency disorders tend to have one infection after another. Some of the conditions that can cause immunodeficiency disorders can be prevented or managed. The information provided in the Immune Disorders Condition Guide is not intended to be a substitute for professional medical advice. A licensed healthcare professional should be consulted for diagnosis of any immune disorder and treatment of any and all medical conditions.