Body Defenders: Our Immune System

What is a virus and how do our bodies help keep us healthy?


  • Make a model of a virus and of white blood cells to demonstrate how the immune system works
  • Learn about how our bodies help keep us safe

Materials Needed:

  • Red, white, and 1 other color of Play-Dough, or DIY play dough (i.e.
  • Q-Tips cut in half (or sub small sticks, etc.)
  • A red piece of paper rolled and taped into a tube
  • Small pom-poms (or sub any small round object: pony bead etc.)


  • A virus is a tiny germ, so small you can’t see it with your eyes – scientists use microscopes to see them up close.
  • Viruses can make us sick, but they need to live inside something (called a host) to survive.
  • When we get sick from a virus, it has gotten into our cells – the tiny things that make up our bodies.
  • The coronavirus is a new type of virus. “Corona” means “crown” in Latin. We call it that because the virus has little spikes that kind of look like a crown.
  • A virus gets into cells with a little spike that kind of acts like a key. Once it is inside of the cells, it makes lots of copies of itself (it does this by “tricking” the cells into using the machinery already there to make copies of itself), which can break out and get inside other cells. At some point, there are so many copies of the virus in the cells that they can’t work properly anymore, which is when we start feeling sick.
  • Viruses only have keys for some types of cells: the coronavirus can only get into cells in our lungs, and some viruses only can get into our stomach cells. That’s why sometimes if animals get sick, humans can’t catch it: the viruses don’t have the right types of “keys”
  • Luckily, our bodies are built to attack viruses. Our immune system is like an army that attacks the virus. Things like a fever, headache, and runny nose are actually signs that your immune system is working hard to get all the virus out of your cells.


  • There are two types of viruses: enveloped and non-enveloped. The big difference is that enveloped viruses (like COVID-19) are more similar to cells, so they can be hard for the immune system to detect and fight. The good news is that the envelope also makes a soft target, which means it’s easier to kill outside the body. That’s why washing hands, using hand sanitizer, and disinfecting surfaces is important for keeping us healthy. There’s a great demo for an extension activity exploring this here:

Activity #1: Build a Model

  1. Ask: How can models help us understand how things work? (i.e. we cannot see the coronavirus because it is too small – a model can help us represent different parts and understand what it looks like even though we cannot see it)
  2. Make some observations about photos of the virus.
  3. Roll playdough into about a 1-inch ball. This represents the virus core. RNA and DNA live in the virus core.
  4. If discussing enveloped viruses, roll out a thin, flat piece of playdough and wrap it around the virus core.
  5. Stick the Q-tips into the playdough ball. These represent the proteins, which act as keys.

Activity #2: The immune system (original source)

  1. Form red blood cells with red playdough by rolling small balls and pressing a small dent in the center
  2. Form some white blood cells by rolling white playdough into spherical balls. The white blood cells should be about 3x as big as the red blood cells.
  3. Next, dump out a bunch of pompoms – a virus invasion!
  4. Use the white blood cells to “attack” the virus by pressing the pompoms into the white blood cells and ensuring they’re fully covered.
  5. After all the germs have been conquered, the red blood cells and white blood cells can go into the red tube of construction paper to model a blood vessel.
  6. Extension: add the other parts of the blood using leftover playdough! Platelets are really small and help form blood clots (help stop bleeding from a cut) and plasma is a liquidy substance that all the parts of the blood swim in.