Home Store Project Ideas Project Guide Ask An Expert Blog Careers Teachers Parents Students

Student Guide: Memory to the Rescue: Investigating How the Immune Response Fights Infection

Downloadable and printable Student Guide PDF.
(In order to access the PDF you need a free Science Buddies account. Please or create a free account.)

Summary

How does your body's immune system help keep you healthy? And how does your immune system's memory make it work better? Find out by making a model of your immune system with magnets, iron filings, and salt!

Useful Vocabulary

  • Immune system: Organs and cells in a person's body that normally defend against germs and harmful microorganisms.
  • Pathogens: Microorganisms (or microscopic organisms) that can make a person sick. Pathogens include harmful bacteria, microscopic fungus, viruses, and more.
  • Immune response: A series of steps the immune system goes through to fight off a pathogen. The immune system needs to recognize the pathogen and then attack and destroy the pathogen.
  • White blood cells: Also called leukocytes, these cells do most of the work in the immune response. There are several different types of white blood cells, each with a slightly different job, including B cells and T cells.
  • Antibodies: Tiny particles made by white blood cells that can attach to, or bind, a pathogen. The pathogen can then be destroyed by white blood cells.
  • Memory cells: Some white blood cells leave a memory cell behind after they destroy the pathogen. The memory cell remembers the pathogen so that white blood cells can make a larger and faster immune response (meaning they make more antibodies) if they encounter the same pathogen again.
    Human Biology science project Drawing of antibodies binding a bacterium.
    Figure 1. During the immune response, antibodies (in blue) bind onto a pathogen (a bacterium here, in red). Once bound onto the pathogen, the antibodies get help from white blood cells to destroy the pathogen. Note: This is a simplified diagram and does not show the true size, complexity, or dimensions of the objects.

Materials

To do this activity you will need:

  • Glass jar with lid, 16 oz. size
  • Salt (1 cup)
  • Measuring cup
  • Measuring tablespoon
  • Iron filings (1 tbsp.)
  • Magnetic tape squares wrapped in plastic wrap with a twist tie (3)
  • Piece of paper

Directions

  1. Use the measuring cup to measure out 1 cup of salt. Fill the glass jar with the salt. The jar should be about half full with salt.
  2. Use the measuring tablespoon to measure out 1 tablespoon (tbsp.) of iron filings and add them on top of the salt in the jar.
Human Biology science project Image of iron filings and salt in a glass jar.
Figure 2. Fill the jar with 1 cup of salt and add 1 tbsp. of iron filings on top.
  1. Put the lid on the jar tightly and mix the salt and iron filings together. Do this by flipping the jar upside down and then right-side up again about ten times (doing about one flip per second) or until the iron filings look evenly spread out throughout the salt in the jar. How do the salt and iron filings look in the jar? Does it look like there is a lot more salt than iron filings?
Human Biology science project  Image of salt and iron filings mixed together in a jar.
Figure 3. After mixing the iron filings and salt together, see how they look in the jar.
  1. In your model of the immune response, the jar represents the human body. The salt represents human cells. The iron filings represent pathogens. Each magnetic tape square (surrounded by plastic wrap), which you will use next, represents many antibodies. Although you are modeling the functions of the immune response, your model is not accurate in terms of size, because in reality human cells are usually much larger than pathogens, and pathogens are usually much larger than antibodies. (Also, many antibodies normally bind onto a single pathogen.)
  2. Put one of the "antibodies" (the prepared magnetic tape squares) in the jar of salt and iron filings. Put the lid on the jar tightly and again flip the jar ten times.
Human Biology science project Picture of a magnetic tape square ('antibody') in a jar of salt and iron filings.
Figure 4. Put an antibody (a prepared magnetic tape square) in the jar, put the lid on the jar, and flip it about ten times.
  1. Carefully take the antibody out of the jar. You may need to tilt the jar to grasp the antibody. Grab the antibody only by the twist tie or the twisted plastic, and do not touch where the iron filings have collected.
  2. As you take the antibody out of the jar, gently turn the antibody upside down so that anything trapped in the twisted plastic wrap falls back into the jar. You can gently shake it to do this, but do not shake it so hard that anything stuck to the magnet gets knocked off.
  3. Look at the antibody. Does it look like there are more iron filings stuck to the magnet than salt? In other words, does it look like the antibody is specifically binding onto the pathogen (the iron filings)?
  4. Hold the magnetic tape square (antibody) over a piece of paper, undo the twist tie, and carefully open up the plastic wrap surrounding the magnet. Carefully position the plastic wrap so that only the iron filings and salt fall onto the paper. Look at what fell onto the paper. Is it mostly iron filings or mostly salt?
  5. Carefully pour the iron filings and salt that fell on the paper back into the jar. Again mix the iron filings and salt together in the jar by putting the lid on the jar tightly and flipping it ten times.
  6. Now take the lid off the jar and put all three antibodies into the jar together. In your model this represents the immune system's memory cells making more antibodies, because they fought this specific pathogen before.
Human Biology science project Picture of three magnetic tape squares ('antibodies') in a jar of salt and iron filings.
Figure 5. Put all three antibodies in the jar together, put the lid on the jar tightly, and flip it about ten times.
  1. Put the lid on the jar tightly and flip it ten more times.
  2. Carefully take each antibody out of the jar, one at a time, as you did before. Again, carefully tilt the jar to grasp the antibodies, taking care not to knock off anything that is bound onto the magnets, and gently turn the antibodies upside down and shake each a little so that anything not stuck to the magnet will fall back into the jar.
  3. Look at each antibody. How does it look similar or different from the first antibody? Does it look like each antibody has more, less, or about the same amount of iron filings and salt stuck to it as the first antibody did?
  4. Hold each magnetic tape square over a piece of paper, untie the twist tie, and open up the plastic wrap surrounding the magnet. Carefully position the plastic wrap so that only the iron filings and salt fall out onto the paper. Now look at what fell onto the paper. Is it more, less, or about the same amount of salt and iron filings as the first antibody? What do you think this tells you about why the immune system creates memory cells?