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What is the immune system?

Your immune system is a large network of organs, white blood cells, proteins and chemicals. These parts all work together to protect you from germs and other invaders. Your immune system also helps your body heal from infections and injuries.

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Function

What does the immune system do

Innate immunity is protection that you’re born with. Your innate immune system is part of your body’s first-line defense. It responds to invaders right away by attacking any organism that shouldn’t be in your body. It doesn’t need prior training to tell the difference between cells that belong in your body and those that don’t.

The white blood cells involved in innate immunity don’t learn to recognize certain invaders. They also have no memory of attacking invaders and don’t offer protection against specific germs (or the infections they cause) in the future.

That’s where acquired immunity comes into play. Acquired immunity, also called adaptive or specific immunity, is protection your body gains (acquires) over time from exposure to germs. Certain white blood cells called lymphocytes remember specific invaders and can tell when they don’t belong in your body. So, if those invaders try to get in again, the lymphocytes can quickly spring into action and work with other cells to eliminate the threat.

Vaccines support your acquired immunity by training its cells to identify and destroy invaders before they make you sick.

How does the immune system work?

When your immune system is working properly, it:

  • Tells the difference between cells that are yours and those that don’t belong in your body.
  • Activates and mobilizes to kill germs that may harm you.
  • Ends an attack once the threat is gone.
  • Learns about germs after you’ve had contact with them and develops antibodies against them.
  • Sends out antibodies to destroy germs that try to enter your body in the future.
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But things don’t always go this smoothly. Sometimes, your immune system doesn’t work properly. For example, it may be too weak to fight off invaders, or it may launch too strong of a response.

Weak immune system

Many different conditions can weaken your immune system and make you more susceptible to infection. Conditions at birth are less common than those that develop later in life, like Type 2 diabetes and cancer.

Overactive immune system

At the other end of the spectrum, your immune system may react too strongly to invaders (real or perceived). It may mount an attack when there’s no invader. Or it may keep attacking after getting rid of an invader. An overactive immune system can lead to problems like autoimmune diseases or allergic reactions.

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Anatomy

The various organs, tissues and cells of your immune system are distributed throughout your body. They all work together to help keep you healthy.

What parts of your body make up the immune system?

Many parts of your body, including immune system organs and cells, work together to keep you healthy. The main components of your immune system are:

  • White blood cells. These immune system cells attack and eliminate harmful germs to keep you healthy. There are many types of white blood cells, and each type has a specific mission in your body’s defense system. Each type also has a different way of recognizing a problem, communicating with other cells and getting their job done.
  • Antibodies. These proteins protect you from invaders by binding to them and initiating their destruction.
  • Cytokines. These proteins serve as chemical messengers that tell your immune cells where to go and what to do. Different types of cytokines do different specific tasks, like regulating inflammation. Inflammation happens when your immune cells are warding off invaders or healing damage to your tissues.
  • Complement system. This is a group of proteins that teams up with other cells in your body to defend against invaders and promote healing from an injury or infection.
  • Lymph nodes. These small, bean-shaped organs are like colanders you use to drain pasta. They filter waste products from the fluid that drains from your tissues and cells (lymph) while keeping the good components, like nutrients. You have hundreds of lymph nodes throughout your body, and they’re a vital part of your lymphatic system.
  • Spleen. This organ stores white blood cells that defend your body from invaders. It also filters your blood, recycling old and damaged cells to make new ones.
  • Tonsils and adenoids. Located in your throat and nasal passage, tonsils and adenoids can trap invaders (like bacteria or viruses) as soon as they enter your body.
  • Thymus. This small organ helps T-cells (a specific type of white blood cell) mature before they travel elsewhere in your body to protect you.
  • Bone marrow. This soft, fatty tissue inside your bones is like a factory for your blood cells. It makes the blood cells your body needs to survive, including white blood cells that support your immune system.
  • Skin. Your skin is a protective barrier that helps stop germs from entering your body. It produces oils and releases other protective immune system cells.
  • Mucosa. This three-layered membrane lines cavities and organs throughout your body. It secretes mucus that captures invaders, like germs, for your body to then clear out.
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What is the immune system?

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There are two main types of pharyngitis. Healthcare providers categorize them based on how long symptoms last:

  • Acute pharyngitis: A sore throat that lasts from about three to 10 days. Most sore throats are acute pharyngitis.
  • Chronic pharyngitis: A sore throat that lasts for more than 10 days (usually several weeks) or that keeps returning after you get better.

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Your immune system is a large network of organs, white blood cells, proteins and chemicals. These parts all work together to protect you from germs and other invaders. Your immune system also helps your body heal from infections and injuries...

Whenever possible, reproduce the Cleveland Clinic logo in full color — using Cleveland Clinic Blue, Green and Black. See the Pantone numbers listed below.

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For 4-color process printing, use CMYK values. For on-screen applications (e.g., video, broadcast), use RGB Video values.

Pantone and CMYK values can be used for printing on both coated and uncoated paper. Although color variations will occur, try to match the colors as closely as possible.

Your immune system is a large network of organs, white blood cells, proteins and chemicals. These parts all work together to protect you from germs and other invaders. Your immune system also helps your body heal from infections and injuries...

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Function

What does the immune system do

Your immune system works hard to keep you healthy. It does this by:

  • Keeping invaders (like germs) out of your body.
  • Destroying invaders.
  • Limiting how much harm the invaders can do if they’re inside your body.
  • Healing damage to your body.
  • Adapting to new challenges and threats.

Invaders your immune system protects you against include:

How does the immune system work?

When your immune system is working properly, it:

  • Tells the difference between cells that are yours and those that don’t belong in your body.
  • Activates and mobilizes to kill germs that may harm you.
  • Ends an attack once the threat is gone.
  • Learns about germs after you’ve had contact with them and develops antibodies against them.
  • Sends out antibodies to destroy germs that try to enter your body in the future.

But things don’t always go this smoothly. Sometimes, your immune system doesn’t work properly. For example, it may be too weak to fight off invaders, or it may launch too strong of a response.

Weak immune system

Many different conditions can weaken your immune system and make you more susceptible to infection. Conditions at birth are less common than those that develop later in life, like Type 2 diabetes and cancer.

Overactive immune system

At the other end of the spectrum, your immune system may react too strongly to invaders (real or perceived). It may mount an attack when there’s no invader. Or it may keep attacking after getting rid of an invader. An overactive immune system can lead to problems like autoimmune diseases or allergic reactions.


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At the other end of the spectrum, your immune system may react too strongly to invaders (real or perceived). It may mount an attack when there’s no invader. Or it may keep attacking after getting rid of an invader. An overactive immune system can lead to problems like autoimmune diseases or allergic reactions.

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