The immune system is complex and pervasive. There are numerous cell types that either circulate throughout the body or reside in a particular tissue. Each cell type plays a unique role, with different ways of recognizing problems, communicating with other cells, and performing their functions. By understanding all the details behind this network, researchers may optimize immune responses to confront specific issues, ranging from infections to cancer.
The immune system can distinguish between normal, healthy cells and unhealthy cells by recognizing a variety of “danger” cues called danger-associated molecular patterns (DAMPs). Cells may be unhealthy because of infection or because of cellular damage caused by non-infectious agents like sunburn or cancer. Infectious microbes such as viruses and bacteria release another set of signals recognized by the immune system called pathogen-associated molecular patterns (PAMPs).
- Innate immunity is the protection that you are born with. It is your body’s first line of defense. It includes barriers such as the skin and mucous membranes. They keep harmful substances from entering the body. It also includes some cells and chemicals which can attack foreign substances.
- Active immunity, also called adaptive immunity, develops when you are infected with or vaccinated against a foreign substance. Active immunity is usually long-lasting. For many diseases, it can last your entire life.
- Passive immunity happens when you receive antibodies to a disease instead of making them through your own immune system. For example, newborn babies have antibodies from their mothers. People can also get passive immunity through blood products that contain antibodies. This kind of immunity gives you protection right away. But it only lasts a few weeks or months.
Sometimes a person may have an immune response even though there is no real threat. This can lead to problems such as allergies, asthma, and autoimmune diseases. If you have an autoimmune disease, your immune system attacks healthy cells in your body by mistake. Other immune system problems happen when your immune system does not work correctly. These problems include immunodeficiency diseases. If you have an immunodeficiency disease, you get sick more often. Your infections may last longer and can be more serious and harder to treat. They are often genetic disorders. There are other diseases that can affect your immune system. For example, HIV is a virus that harms your immune system by destroying your white blood cells. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome). People with AIDS have badly damaged immune systems. They get an increasing number of severe illnesses.
The immune system produces antibodies that attach to the linings of joints. Immune system cells then attack the joints, causing inflammation, swelling, and pain. If untreated, rheumatoid arthritis causes gradually causes permanent joint damage. Treatments for rheumatoid arthritis can include various oral or injectable medications that reduce immune system overactivity.
People with lupus develop autoimmune antibodies that can attach to tissues throughout the body. The joints, lungs, blood cells, nerves, and kidneys are commonly affected in lupus. Treatment often requires daily oral prednisone, a steroid that reduces immune system function.
The immune system attacks the lining of the intestines, causing episodes of diarrhea, rectal bleeding, urgent bowel movements, abdominal pain, fever, and weight loss. Ulcerative colitis and Crohn’s disease are the two major forms of IBD. Oral and injected immune-suppressing medicines can treat IBD.
The immune system attacks nerve cells, causing symptoms that can include pain, blindness, weakness, poor coordination, and muscle spasms. Various medicines that suppress the immune system can be used to treat multiple sclerosis.
Immune system antibodies attack and destroy insulin-producing cells in the pancreas. At diagnosis, people with type 1 diabetes require insulin injections to survive.
The immune system attacks the nerves controlling muscles in the legs and sometimes the arms and upper body. Weakness results, which can sometimes be severe. Filtering the blood with a procedure called plasmapheresis is the main treatment for Guillain-Barre syndrome.
Similar to Guillian-Barre, the immune system also attacks the nerves in CIDP, but symptoms last much longer. About 30% of patients can become confined to a wheelchair if not diagnosed and treated early. Treatment for CIDP and GBS are essentially the same.
In psoriasis, immune system blood cells called T-cells collect in the skin. The immune system activity stimulates skin cells to reproduce rapidly, producing silvery, scaly plaques on the skin.
The immune system produces antibodies that stimulate the thyroid gland to release excess amounts of thyroid hormone into the blood (hyperthyroidism). Symptoms of Graves’ disease can include bulging eyes as well as weight loss, nervousness, irritability, rapid heart rate, weakness, and brittle hair. Destruction or removal of the thyroid gland, using medicines or surgery, is usually required to treat Graves’ disease.
Antibodies produced by the immune system attack the thyroid gland, slowly destroying the cells that produce thyroid hormone. Low levels of thyroid hormone develop (hypothyroidism), usually over months to years. Symptoms include fatigue, constipation, weight gain, depression, dry skin, and sensitivity to cold. Taking a daily oral synthetic thyroid hormone pill restores normal body functions.
Antibodies bind to nerves and make them unable to stimulate muscles properly. Weakness that gets worse with activity is the main symptom of myasthenia gravis. Mestinon (pyridostigmine) is the main medicine used to treat myasthenia gravis.
The immune system attacks and damages blood vessels in this group of autoimmune diseases. Vasculitis can affect any organ, so symptoms vary widely and can occur almost anywhere in the body. Treatment includes reducing immune system activity, usually with prednisone or another corticosteroid.