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Build-Your-Own Immune System Defense Game STEM Activity

Every day, your child’s immune system is hard at work defending their body from germs, viruses, and bacteria. But what if they could see how that defense system works, by building it with everyday materials?

This Build-Your-Own Immune System Defense Game is a creative, engaging STEM activity that helps kids understand complex biology through play. Designed in the spirit of Little Medical School®’s hands-on curriculum, this at-home challenge turns learning about the immune system into a dynamic, interactive experience.

 

The Immune System for Kids’ STEM Learning

The immune system includes:

  • Structures (skin, mucus, blood cells)

  • Processes (attacking invaders, forming antibodies)

  • Cause-and-effect relationships (how germs spread and how the body responds)

 

Materials You’ll Need (All Household Items)

  • 1 bag of cotton balls (white blood cells)

  • 1–2 cups of marbles or small balls (germs)

  • Plastic cups or small containers (barriers like skin, mucus, and stomach acid)

  • Paper towel or sponge pieces (filters)

  • Tape or painter’s tape (to build pathways)

  • A baking tray or shallow box to assemble the “battlefield”

  • Optional: markers to label each defense layer

 

Build Your Immune System Game: Step-by-Step

Step 1: Create the “Body Pathway”

Use tape to create a winding path inside the tray or box. This path represents the spaces germs travel through when entering the body.

Activity Tip:
Ask kids: “Where do germs enter the body? What parts protect us first?”

Step 2: Add the Body’s First Lines of Defense

Along the beginning of the pathway, place:

  • Paper towels/sponge strips ? skin barrier

  • Wet cotton ball pieces ? mucus (sticky to trap germs)

  • A cup labeled “Stomach Acid” ? acid that destroys invaders

Kids must physically place germs (marbles) into each area to see whether they get “trapped” or “broken down.”

Science Connection For Learning:
Skin and mucus make up the body’s “innate” or first-line defenses, systems we are born with that protect us immediately.

Step 3: Set Up the “White Blood Cell Zone”

Scatter cotton balls throughout the mid-section of the maze. These represent white blood cells.

When a marble (germ) touches a cotton ball, it’s considered “neutralized.”

Extend the Challenge:
Give white blood cells “speed boosts” by allowing cotton balls to move if placed on a spoon or stick, a fun metaphor for activated immune response.

Step 4: Add “Antibodies” for Reinforcement

Choose a few cotton balls to represent antibodies, they stay in fixed positions and can block multiple germs at once.

Research shows antibodies are specially shaped proteins that remember invaders and fight them off faster next time. Kids will intuitively see how “memory defense” works when antibodies repurpose the pathway.

Step 5: Start the Game!

Kids drop marbles (germs) into the start of the pathway and roll them forward through the body. Their goal is to reach the “Healthy Body Zone”… but your immune defenses are there to stop them.

They’ll quickly learn:

  • Which barriers are strongest

  • Which weaknesses allow germs to pass

  • How the immune response ramps up in different areas

  • Why our bodies use multiple layers of defense

Step 6: Make It Competitive

  • Round 1: Germs vs. body

  • Round 2: Add more white blood cells

  • Round 3: Add more antibodies

  • Round 4: Introduce new “strains” (different-colored marbles)

Kids love seeing how strategy changes with each round.

 

More on the Science Behind This Activity

1. Innate Immunity (Immediate Response)

Skin, mucus, stomach acid, represented by your barriers. Resource: CDC – How Germs Spread & How the Body Stops Them

2. Adaptive Immunity (Learned Response)

White blood cells + antibodies, your active defenses. Resource: NIH – Understanding the Immune System

 

Little Medical School®’s Leadership in STEM

Little Medical School® is known for transforming complex healthcare concepts into fun, accessible, hands-on learning for children. Activities like this connect STEM, health science, and inquiry-based play in a way that builds both understanding and confidence.

Through simple household items, children get to:

  • Think like immunologists

  • Experiment like biomedical engineers

  • Problem-solve like healthcare professionals

  • Learn by doing, touching, modifying, testing

This is exactly the philosophy behind our after-school programs, summer camps, and enrichment workshops across the Treasure Coast and South Florida.

 

 

Get Involved with Little Medical School® of the Treasure Coast

Are you passionate about inspiring the next generation of healthcare heroes? We’re expanding our impact across South Florida to bring hands-on health and STEM education to life.

  • School Partnerships: Interested in bringing our after-school clubs or enrichment programs to your campus? Let’s chat to create engaging, standards-aligned experiences for your students. Get in touch.

  • Sponsorship & Collaboration: Do you have an idea for collaboration or want to support our work? Since 2023, Little Medical School® of the Treasure Coast has empowered over 3,200 students across South Florida through hands-on healthcare education. Get in touch.

  • Instructor Positions: We’re seeking pre-med, pre-health, and pre-education university students who want real leadership experience teaching future doctors through play. Apply here.

  • Volunteer Opportunities: Join our volunteer team and gain valuable experience in healthcare outreach, youth mentorship, and community health education. Apply here.

  • Share Your Moments: We love seeing our students in action! Tag us in your photos or posts from our programs on social media.

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