How does your immune system work?

What’s going on inside our bodies that protects us from sickness?

By Barrett White

Your body has a special defense inside it. Like an army that exists just to protect you! Existing microscopically inside you, this small-but-mighty army is your immune system.

Your immune system exists to protect you from outside threats, like bacteria, viruses, and fungi. Your immune system is made up of different organs, cells, and proteins, all working together to identify these threats and prevent them from making you sick.

There are two main parts of your immune system: There’s the innate immune system, which you were born with, and the adaptive immune system, which you develop over the course of your life as you’re exposed to those outside threats or infections. 

The white blood cells of your immune system, or B-lymphocytes, make a special kind of protein called antibodies. These antibodies protect you from specific infections once you’ve been exposed to them. The first time the body is infected with a certain germ, it can take several days for the immune system to make and use all the tools needed to fight the infection. After the infection, the immune system remembers what it learned about how to protect the body against that disease.

Vaccines introduce dead versions of viruses into your body so that your immune system can create the necessary antibodies. This way if you encounter the actual virus, you may have better immunity.

The cells of both parts of the immune system are made in different organs of the body, including:

  • Adenoids. Two glands located at the back of the nasal passage.
  • Bone marrow. The soft, spongy tissue found in bone cavities.
  • Lymph nodes. Small organs shaped like beans, which are located all over the body and connect via the lymphatic vessels.
  • Lymphatic vessels. A network of channels all over the body that carries lymphocytes to the lymphoid organs and bloodstream.
  • Peyer patches. Lymphoid tissue in the small intestine.
  • Spleen. A fist-sized organ located in the belly (abdominal) cavity.
  • Thymus. Two lobes that join in front of the windpipe (trachea) behind the breastbone.
  • Tonsils. Two oval masses in the back of the throat.