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What is the immune system?

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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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