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Facilitator/Educator Guide: What are the Odds? Modeling the Chances of Getting an Autoimmune Disease

Autoimmune diseases are fairly common, affecting more than 23.5 million people in the United States, or about 1 in 13 people. These diseases develop when a person's immune system attacks the person's own body by accident. Model how this can happen using M&M's® candies and a die.

Activity's uses: Demonstration or small group exploration
Area(s) of science: Life Science, Math & Computer Science
Difficulty level:
Prep time: < 10 minutes
Activity time: 20-30 minutes
Key terms: Health, autoimmune diseases, pathogens, immune system, models, illness, probability, medical drugs
Downloads and Links: Facilitator / Educator Guide PDF.
Student Guide web page or PDF.

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Background Information

A person's immune system is made up of different cells and organs in their body that normally defend them against pathogens (germs and harmful microorganisms). The immune system goes through a process called the immune response to fight off a pathogen. Most of the work is done by white blood cells. There are several different types of white blood cells, including B cells and T cells; collectively, the different types of white blood cells are also called leukocytes. White blood cells must find the pathogen in the body, tell it apart from the human cells, and then make antibodies, which are tiny particles that attach, or bind to, the pathogen. Once bound to the pathogen, the antibodies get help from white blood cells to destroy the pathogen.

The process by which the immune system tells pathogens apart from human cells is called self/non-self recognition. If it fails, it can cause autoimmune diseases (or an infection). When the immune system accidentally makes an antibody that binds to its own healthy human cells, it is called autoimmunity, or an autoimmune response. (The antibody is called an autoantibody.) Autoimmunity is common and usually not serious, but if it is not stopped by the body, it can turn into an autoimmune disease, which is when the immune system chronically attacks healthy cells in the body. A person's genetics can make them predisposed, or more likely, to get an autoimmune disease. Environmental factors (such as where they live, what they eat, and things they are exposed to) can also affect whether a person gets an autoimmune disease.

One common autoimmune disease that you could discuss with your students is diabetes mellitus type 1, more commonly known as type 1 diabetes. Type 1 diabetes is caused by the immune system attacking and destroying cells that normally make insulin (beta cells in the pancreas). The incidence varies from about 0.013% of people in northern Europe and the United States, to a high of 0.035% of people in Scandinavia and a low of 0.001% of people in Japan and China. There is a genetic component, but it is not completely genetic, and so environmental factors matter (if it were completely genetic, then if one identical twin had diabetes, the other twin would also get it; but medical records show that, in reality, if one identical twin has diabetes, the other twin is only 30–50% likely to also get it. This, and other medical evidence, shows that both genetics and environment matter). Before the effects of type 1 diabetes become visible, autoantibodies can be detected. However, even if a person has autoantibodies, they are not guaranteed to get type 1 diabetes, but the person does have an increased likelihood of developing diabetes over their lifetime. The more types of autoantibodies that are present, the greater the risk.

Here are three checkpoints that the immune system has in order to stop an autoimmune response from becoming an autoimmune disease. Note that these are simplified versions of what the immune system actually does.

  1. Checkpoint 1: Sometimes white blood cells (specifically B cells, which are made in the bone marrow, or T cells, which are made in the thymus) are made that have autoimmunity, meaning their antibodies bind human cells. The body must destroy them before they escape from the bone marrow or thymus, or they can cause an autoimmune disease.
  2. Checkpoint 2: Right before an immune response is triggered to fight a pathogen, white blood cells (called regulatory T cells) make sure that other white blood cells are not accidentally attacking the body's own cells. They need to do their job correctly to prevent an autoimmune disease.
  3. Checkpoint 3: After a pathogen is destroyed in the body, white blood cells (specifically activated T cells and B cells) must destroy themselves (through a process called apoptosis) to stop the immune response, or it could lead to an autoimmune disease.

In this science activity, students will use M&M's candies (other colored objects may be substituted) and a die to make a model of the immune system to find out how a person's genetics (and other factors) affect whether they get an autoimmune disease or not.

For Discussion

This science activity can serve as a starting point for a variety of science and health discussions. Here are a few examples of questions that can be used to start a discussion:

  • Can you think of examples of autoimmune diseases? (Some common ones include lupus, Graves' disease, Hashimoto's disease, rheumatoid arthritis, diabetes type 1, and celiac disease.)
  • In the immune response, what do antibodies do?
  • How can an autoimmune disease be caused and treated?
  • Do people often have an autoimmune response that does not turn into an autoimmune disease?
  • How are autoimmune diseases treated?

Materials

Needed for preparing ahead:

  • M&M's candies (one 1.69 oz. package of regular M&M's should be sufficient for each demo or small group); other small colored objects may be used as a substitute
  • Bowl or cup (1 per demo or small group)

Needed for each demo or small group at the time of the science activity:

  • Bowl or cup of M&M's candies with an equal number of each color (1)
  • Six-sided die (1)
  • Pencil or pen (1)
Photograph of all materials for activity  immune diseases
Figure 1. You need only a few simple household materials to do this fun science activity.

What to Do

Prepare Ahead (< 10 minutes)

  1. Open the package of M&M's and place three M&M's candies of each color (red, green, yellow, brown, blue, and orange) into a bowl or cup. If your package does not have at least three of each color, you could use fewer M&M's candies, as long as there is an equal number of each of the six colors.
  2. For each demo or small group, prepare a bowl of M&M's candies, making sure there is an equal number of each color in each bowl.
Photograph of M&M candies in bowl
Figure 2. Place three M&M's candies of each color into a bowl or cup. Alternatively, you can use fewer M&M's candies, as long as there is an equal number of each color.
  1. Print out a copy of the Student Guide for each demo or small group; it contains data tables and a flowchart that students will need to do the activity.

Science Activity (20-30 minutes)

  1. Each classroom demo or small group should have a bowl or cup of M&M's candies with an equal number of each color, a six-sided die, a pencil or pen, and a copy of the Student Guide.
  2. Explain to students that they will be modeling the immune system to investigate autoimmunity and how autoimmune diseases can be caused. They will be filling out two data tables, and each data table will represent a group of 20 people with a different genetic predisposition that gives them a different increased risk of getting an autoimmune disease. One group has a higher risk at two of the three checkpoints for preventing an autoimmune disease, while the other group is not at this higher risk at any of the three checkpoints (but still has some risk of developing an autoimmune disease).
  3. Tell students they will fill out the "Normal Chances of Autoimmunity Group" data table first.
Normal Chances of Autoimmunity Group
Step in the ModelPerson Number
  12345678910 11 12 13 14151617181920
Setup What color was picked?                        
Checkpoint 1 Color match? (Yes/No)                        
If yes, what was the die number? (1 to 6)                        
Checkpoint 2 Color match? (Yes/No)                        
If yes, what was the die number? (1 to 6)                        
Checkpoint 3 Color match? (Yes/No)                        
If yes, what was the die number? (1 to 6)                        
Did the person get an autoimmune disease? (Yes/No)                        
Table 1. This data table represents a group of 20 people who do not have a higher risk at any of the autoimmune disease checkpoints, but they still have some risk of developing an autoimmune disease. This data table will be filled out first. Download Table 1 (pdf).
  1. To fill out the data table, have students follow the directions in the "Autoimmunity Model" flowchart, below. Have them go through the flowchart for each of the 20 people in the data table. Use these steps to help guide students through the process:
    1. In the "Setup" part, make sure students write the color of the candy they picked in their data table for each person.
    2. Make sure they write their other results in their data table as they test the model.
    3. If they do not need to roll a die when testing certain checkpoints, skip the "If yes, what was the die number?" row for that person.
    4. If students have a color match and roll a die, testing should end for the person only if a 6 is rolled on the die. This means the person got an autoimmune disease.
    5. Make sure students also look at the blue "What it represents" boxes so they know what they are modeling.
    6. At the beginning of the "Setup" and each checkpoint, make sure the candy is returned to the bowl and there is still an equal number of each color.
Flowchart for testing the autoimmunity model
Figure 3. This is a flowchart of the model students will use in this activity. The "What it represents" blue boxes explain what each part of the model represents. As the students follow the steps in the model and fill out each data table, make sure they keep the information in the boxes in mind.
  1. You can have students briefly discuss their results when they have filled out the "Normal Chances of Autoimmunity Group" data table.
  2. Next, have them look at the "Higher Risk at Checkpoints 2 and 3 Group" data table.
Higher Risk at Checkpoints 2 and 3 Group
Step in the ModelPerson Number
  12345678910 11 12 13 14151617181920
Setup What color was picked?                        
Checkpoint 1 Color match? (Yes/No)                        
If yes, what was the die number? (1 to 6)                        
Checkpoint 2 Color match? (Yes/No)                        
If yes, what was the die number? (1 to 6)                        
Checkpoint 3 Color match? (Yes/No)                        
If yes, what was the die number? (1 to 6)                        
Did the person get an autoimmune disease? (Yes/No)                        
Table 2. This data table represents a group of 20 people who are at higher risk for developing an autoimmune disease at checkpoints 2 and 3. Download Table 2 (pdf).
  1. Have students repeat the modeling process to fill out the "Higher Risk at Checkpoints 2 and 3 Group" data table, but this time if they have a color match and roll a die, have them do the following:
    1. If the color match occurs at checkpoint 1, then testing should end for the person only if a 6 is rolled on the die, meaning the person got an autoimmune disease.
    2. If the color match occurs at checkpoint 2 or 3 (meaning the person is at higher risk), then testing should end for this person if a 2, 3, 4, 5, or 6 is rolled on the die (but not if a 1 is rolled). This means the person got an autoimmune disease.
  2. Again, you can have students briefly discuss their results when they have filled out the second data table.
  3. Have students calculate the percentage of people who got an autoimmune disease for each data table. To do this, they can count up the number of times they wrote "Yes" in the bottom row, then divide that number by 20. For example, if in a data table 3 people got an autoimmune disease, the percentage would be 3 divided by 20, which is 0.15 or 15%.
  4. You can ask students to discuss their results, such as whether there were people with two checkpoints at higher risk who did not get an autoimmune disease, whether people with higher risk at none of the checkpoints ever got an autoimmune disease, and if there were many times when a person had an autoimmune response that did not turn into an autoimmune disease (i.e., the M&M's colors matched but the die roll was not high enough to cause an autoimmune disease).

Expected Results

For each data table, the chances of matching the M&M's candy color and triggering an autoimmune response is the same (1 out of 6, since there are six M&M's candy colors). However, the "Higher Risk at Checkpoints 2 and 3 Group" data table should have had a higher occurrence of autoimmune diseases because checkpoints 2 and 3 had greater odds of having an autoimmune response turn into an autoimmune disease (5 out of 6 compared to 1 out of 6, based on the die roll). For example, students may have seen about 1 in 20 people develop an autoimmune disease in the "Normal Chances of Autoimmunity Group" data table and about 6 or 7 people develop an autoimmune disease in the "Higher Risk at Checkpoints 2 and 3 Group" data table, although their numbers may vary due to the randomness involved in the model.

For Further Exploration

This science activity can be expanded or modified in a number of ways. Here are a few options:

  • Have students repeat this activity, but pick different checkpoints to be at higher risk, such as only one checkpoint, two different checkpoints, or all three checkpoints. How do their results change as the number of checkpoints at higher risk increases?
  • In this activity, students used probability, or the likelihood or chance that a certain event will happen, but they did not mathematically calculate the probabilities they tested. You could have students calculate, for example, the probability of rolling a 1 on a six-sided die, or picking a certain colored M&M's candy from a bowl with six candies, each a different color. How do these probabilities relate to the model they tested?
  • Have students pick a specific autoimmune disease and do some research on it. With an adult's help, they can try to find out what is known about the causes of the autoimmune disease, how often a person gets it, and how it is treated. See if students can model the cause of the disease using or changing the original model. Tip: One autoimmune disease that is fairly well understood is celiac disease.

Credits

Teisha Rowland, PhD, Science Buddies
Sponsored by a generous grant from Amgen

M&M's is a registered trademark of Mars, Incorporated.