October is Breast Cancer Awareness month, so to promote awareness and education, I have illustrated some of the ways in which our immune systems interact with cancer! If you enjoy this post, please consider supporting my Kickstarter campaign to publish and distribute my illustrated immunology book. I promise you’ll learn a lot, and you’ll have tremendous fun playing with immune cell playing cards.
Cells are your body’s tiny building blocks that make you who you are.
Cancer cells are your own body’s cells that have become mutated. The DNA (genetic code) of these cells has changed and the the translators inside the cell are now translating the new code into messengers (“proteins”) that are sending haywire signals! Every messenger, whether it’s normal or haywire, is shown off by your cells for your immune system to come by and scan, to see whether that cell is normal, cancerous, infected with a virus, etc. So, guess what? Just like when someone gets a cold, if someone gets cancer, their immune system also sees that there is something wrong! How does this work? Enter: the T cell.
When T cells are growing up, any T cells that react strongly to normal proteins are not allowed out into your body – they are eliminated. So, the only T cells floating around your body are ones that will only activate when they find not normal proteins.
T cells scan to see what other cells are showing off. Normally, other cells are just showing off their normal, non-mutated bits. (Click any of the images below to make them larger.)
Cancerous cells show off pieces of their mutated messengers in little hands (“MHC receptors”) that only T cells can recognize. This activates T cell, who shoots toxic pellets to destroy the cancer cell and rallies up other immune cells to come help!
Your other immune cells race in to try to save the day! They get off to a good start! But sometimes they’re not fast enough, and the crafty cancer cell evolves ways to escape your immune system.
One way that cancer cells try to escape the immune system is by sending a “DESTROY” signal to T cells (technically called PD-L1). Your normal immune cells naturally have the ability to turn other cells off, and this can be really useful and helpful to you – for example, during pregnancy, so your immune system doesn’t see the fetus as “foreign” and start to attack. It can also be useful to engage this “OFF” signal if you receive an organ transplant, so that your immune cells don’t reject the new organ.
But some crafty cancer cells have also learned how to turn the immune system off. They flash this PD-L1 “OFF” signal at T cells, and this destroys the T cells.
One exciting cancer treatment that has shown tremendous benefit in patients involves blocking this “OFF” signal on the cancer cells, so that this “OFF” signal doesn’t touch the T cells, and the T cells continue to do their job.
Another way cancer cells try to hide from your immune system is by hiding their arms. Remember those arms that are showing off mutated (or normal) proteins? Well, they hide them… and then T cell can’t see them to become activated. Luckily, we’re not solely at the mercy of T cells for activation. Enter: Natural Killer Cell.
Natural Killer Cells are so friendly! They go around shaking hands with all of the other immune cells.
But remember what we said about crafty cancer cells? They hide their hands to avoid detection by T cells! And guess what? When any cell doesn’t want to shake hands, Natural Killer Cell knows there’s a problem, and shoots toxic pellets at that cell!
But even with Natural Killer Cell helping to save the day, your body still needs more immune cell help. Let’s bring it back home to a breast cancer example, in honor of Breast Cancer Awareness month. Sometimes a mutated protein of a cancer cell happens to be one that is on the surface of the cancer cell just naturally – maybe it’s involved in receiving signals from other cells, and so just lives on the outside of the cell. This exposes it quite nicely for therapeutic drugs to bind – for example, antibodies.
Antibodies are tags. In your body, B cells (another immune cell) naturally makes antibodies to tag bacteria, viruses, and infected or mutated cells. Scientists have learned how to generate specific antibodies in the lab, and these are now successfully being used in the treatment of cancer and autoimmune conditions – one example being breast cancer. Some breast cancer cells have too much of a protein on their surface called HER2. When patients with this type of breast cancer are given an antibody that binds to HER2, this flags the HER2-overexpressing cancer cells to be eaten by the big eater immune cells (“phagocytes”).
And does that little blue antibody look familiar? That’s because the drug we talked about above that blocks the “OFF” signal is also an antibody.
We’ll pause here, but rest assured this is not the end of the story. There are many other exciting ways in which researchers are leveraging the immune system in the fight against cancer, and there will be more illustrations to come!
If you’ve enjoyed this story, please considering supporting my Kickstarter campaign to raise funds to publish my illustrated immunology book. I would love to spread the joy of learning about the immune system far and wide!
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