Monday, May 01, 2017

Explaining CAR T-cell therapy with marshmallows

Last week, I had fun giving a guest lecture at my daughter's preschool on some cutting edge synthetic biology research. Part of what made it so fun was figuring out how to communicate the essence of the subject on an appropriately comprehensible level.

My daughter's class has been learning about the body, things like muscles and bones and the heart and blood.  One day a few weeks ago, she came home bubbling with excitement about having made blood out of candy that day: into some diluted corn syrup (plasma), they put mini-marshmallows to be white blood cells, red cinnamon candies to be red blood cells, and sprinkles to be platelets. I thought this sounded awesome, and it inspired me to build on that for a lesson about CAR T-cell therapy.


For this lesson, you will need white, red, green, and orange mini-marshmallows, food coloring, and toothpicks. The white marshmallows are white blood cells, the pink ones are healthy cells, the green ones are germs, and the orange ones are cancer cells.


Dip the toothpicks into the food coloring, then poke them into marshmallows to make patterns of three colored dots on the marshmallows. Put patterns on the marshmallows as follows:

  • Give all of the pink healthy cells the same pattern.
  • Give the orange cancer cells a pattern that's almost the same as the healthy cells---but with one difference.
  • Give the germs patterns that are quite different from the pink healthy cells.
  • Give the white blood cells patterns that match germs, but not the healthy cells or cancer cells.

Remember that marshmallows can get flipped around, so "red-red-blue" is effectively the same as "blue-red-red"!


You should now have a bunch of marshmallows with patterns on them.  The lesson goes like this:

  • All cells have patterns of chemicals on their outsides (Show some patterns).
  • White blood cells tell which cells are diseases by matching patterns (Show some white blood cell patterns).
  • A white blood cell leaves your healthy cells alone because they don't match (Show a white blood cell not matching a healthy cell)
  • The white blood cells learn the patterns of diseases and when they match the germs (Show a white blood cell matching a germ), they kill the germ (Eat the germ marshmallow).
  • But cancer cells are tricky, and sometimes their patterns are too close to healthy cells for the white blood cells to learn their patterns (Show how the cancer cell and healthy cell patterns are similar).
  • But now there is a new type of medicine people are trying to make work, where we can take some white blood cells out and teach them a new pattern to recognize (Take a white blood cell and mark it with the cancer pattern).
  • Now we put the white blood cells back in, and they recognize the cancer (Show how the pattern matches now) and kill it! (Eat the cancer marshmallow).
That's CAR T-cell therapy in a nutshell in 5-7 minutes, minus all the details and the cautions and concerns. I had great time teaching this class, and these 3-5 year old kids asked really good questions, like "Does everybody have white blood cells?" and "How do you teach the cells the patterns?" so I think they learned.  

And as I was writing this, my daughter arrived home, bringing a heartmeltingly lovely thank you card her classmates had made.


I think that her class got it.  Science communication win!