What is the immune system? A guide to your body's first-line of defense against infection
immune systemis a complex network of cells, tissues, and organs that fight off infection.
- Your immune system can be affected by sleep, nutrition, hormones, and exercise.
- You can help improve your immune system, but some people are chronically immunocompromised.
Here's what you need to know about your immune system and how it functions.
Your immune system, explainedThe immune system is your body's internal defense system. According to the Cleveland Clinic, your immune system primarily does two things:
- It protects you against germs and tries to keep you from getting sick.
- If you do get sick, it fights the infection to help you recover.
These are some of the major components of your immune system:
- Skin: Your skin is the first line of defense against germs or toxins. It acts like a barrier that prevents germs from entering your body. It also secretes fluids and other substances that destroy germs.
- Mucous membranes: Your respiratory, reproductive, urinary, and digestive tracts are lined with mucus, which traps germs and expels them. For example, when you have a cold, your body produces mucus to flush germs out of your nose, sinuses, and airways.
- White blood cells: These cells are a key part of your immune system. They locate, identify, and attack germs. There are several types of white blood cells; each one has a specific role to play in your immune response.
- Lymph nodes: These are small glands located all over your body, including in your armpit, neck, and groin regions. They are part of your lymphatic system, which filters out germs via a clear, watery fluid known as lymph. This process can help prevent germs from reaching other parts of your body.
- Spleen: Your spleen produces, stores, and dispatches white blood cells. For instance, if your body detects germs in your bloodstream, your spleen and lymph nodes manufacture and dispatch thousands of white blood cells to fight them.
- Tonsils: Located in your throat, your tonsils trap harmful germs as soon as they enter your body, fighting them to prevent respiratory infections like influenza (flu) and pneumonia.
- Bone marrow: Your bone marrow produces several different types of immune cells, including white blood cells. Millions of new blood cells are produced in your bone marrow and added to your bloodstream every day.
- Thymus: Located behind your breastbone, this small organ produces white blood cells that catalogue germs and remember them in future, so that it's easier for your body to fight those germs if they attack you again.
How does your immune system fight infection?If germs get past your defenses, your body launches an immune response to fight them. This involves several types of white blood cells:
- B lymphocytes: These cells produce antibodies, which are special proteins designed to identify and weaken specific germs.
- T lymphocytes: These cells attack the germs identified by the antibodies. They also release cytokines, which are small proteins that orchestrate your entire immune response by controlling the growth and activity of all your blood cells and immune cells.
- Phagocytes: These cells engulf germs and destroy them.
"The generation of long-lasting protective memory is one of the most unique and important characteristics of the immune system. Memory is essential in allowing individuals to defend themselves from infections to which they have previously been exposed," says Tulip Jhaveri, MD, who specializes in pathology and infectious diseases.
Vaccines help the body develop immunity to germs and infections. This is called immunization and it counts on your immune system's memory. Though different vaccines take different approaches to the immunization process, they all trigger your immune response to fight off a particular kind of illness (like measles, smallpox, etc.).After you receive a vaccine, your body remembers how to fight that particular germ and generates a long-lasting immune response. Certain vaccines require a booster shot, which jogs your immune system's memory.
Jhaveri says that recurring illnesses could indicate that one's immune system isn't functioning as it should. Some signs of a weakened immune system include:
- Frequent or prolonged colds
- Recurring gastrointestinal problems like gas, constipation, or diarrhea
- Slow healing of wounds
- Frequent infections, like pneumonia, ear infections, or sinusitis
- Persistent fatigue
- High stress levels
- HIV and AIDS, which damage immune cells, making your body vulnerable to other infections
- Asthma, which causes your immune system to severely overreact to harmless substances
- Leukemia and lymphoma, which affect the normal functioning of your lymphocytes (white blood cells)
- Cancer treatments, like radiation and chemotherapy, which can also damage and destroy immune cells in the process of destroying cancer cells
- Bone marrow or organ transplants, which necessitate deliberately weakening the patient's immune system so it doesn't reject the donated cells
- Smoking, which harms your immune system and raises your chances of developing an illness
Sometimes, the immune system is unable to differentiate between harmful substances and healthy tissues, causing it to attack and destroy healthy cells, which is known as autoimmune disorder. There are over 80 types of autoimmune disorders - some of the more common ones include Type 1 diabetes, multiple sclerosis, lupus, rheumatoid arthritis, and celiac disease.
Insider's takeawayYour immune system consists of several components working together to fight off infection-causing germs. One of the most remarkable characteristics of the immune system is that it is able to remember how to defeat germs it has encountered before; a process by which you develop immunity to that illness. Vaccination, also known as immunization, relies on your immune system's memory to help build immunity against harmful germs that cause illnesses.
Certain health conditions and medical treatments, as well as factors like age, smoking, and pregnancy can compromise your immune system and its ability to function. Frequent illnesses and chronic fatigue are some of the signs of a weakened system. Blood tests can help determine whether your immune system is functioning as it should.Important: Popular discourse offers plenty of theories about boosting immunity, some true, some false, and some unsubstantiated. For instance, multivitamins are believed to boost immunity; however Jhaveri says they don't really help as much as was once believed. Jhaveri says your best chance at boosting your immune system is to eat a healthy diet, get plenty of sleep, exercise regularly, stop smoking, limit your alcohol consumption, and reduce stress.
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