How Your Immune System Fights Infection

Medically Reviewed by Sanjay Ponkshe on March 15, 2024
2 min read

Stuff happens. You nick your skin and bacteria get in. Or you rub your eyes, not realizing that the doorknob you touched had a cold virus on it. Or you ate something that maybe wasn’t cooked or cleaned as well as it should have been.

And just like that, you’ve got an unwanted guest in your body.

Your immune system steps in, like a bouncer who means business. It releases white blood cells and other chemicals that destroy these threats. Or it causes a reaction, like a sneeze, to boot out a virus in your nose.

It’s an elite squad of agents that zap invaders -- like bacteria, viruses, and fungi -- ASAP. They zoom through your body and defend you.

Germs look for ways to get under your skin -- literally. They could get in through a cut, ride in on something you ate, filter through the air, or wait on a coin for you to touch it and then rub your eyes.

Once inside, they start to breed. You’re infected, and it can make you feel sick.

Your immune system should know that there’s a problem. It reads a tell-tale “fingerprint” of proteins on the surface of cells, so it can tell the difference between your own cells and what shouldn’t be there. 

Your white blood cells aim to destroy the unwelcome guests.

They get their start in your bone marrow. They have a short life -- ranging from a few days to a few weeks -- so your body constantly makes more. There are different types, and they all have the same goal: to fight infection.

They wait, poised for duty, in many different places in your body, including your:

  • Thymus
  • Spleen
  • Tonsils
  • Blood vessels
  • Lymph nodes
  • Small intestine
  • Adenoids

Your lymphatic system is like an inner highway that carries white blood cells through your body.

When you’re sick, you might notice your lymph nodes -- small glands in your neck, groin, armpits, and under your chin -- are swollen. This is normal. It means your immune system has kicked into high gear to get rid of infection.

Lymph nodes are also filters for your immune system. They catch germs and dead or damaged cells and destroy them.

Your white blood cells lock on to the germs in order to absorb or destroy them. They produce antibodies that latch onto the germs.

Experience makes your immune system stronger. The first time your body comes into contact with a certain type of germ, your immune response may take a while. You might need several days to make and use all the germ-fighting parts you need to get rid of your infection. It takes time to hack the germ’s code and destroy it.

If you come across that same germ later on, your body will remember and fight it off faster, so you can get over the infection and feel better. Mission accomplished!