Teaching Immunology With an Easter Egg Hunt
This is a story to explain the concept of chemotaxis. Neutrophils are a type of cell that can actually move around inside your body. They live in your blood vessels. And if you get a cut that lets germs (bacteria) in, the cells in your finger send out signals calling for neutrophils to come help. Those signals are little molecules called chemokines.
Here’s how I explain it: imagine you wanted to go on an Easter egg hunt, and we were floating down a river in a canoe. You spot an egg on the shore — “Stop! Let’s get that egg!” — so we land the canoe and go get it. Then you spot another egg off in the woods, so you run over and put it in your basket. Now imagine you look up from picking up that egg, and you see two more eggs to your left and ten to your right. Which way do you run?
“To the right!”
So how did all those eggs get out there? Imagine the Easter Bunny is standing at the top of a hill in the middle of the woods with a giant pile of eggs, rolling them downhill one at a time. Each egg rolls until it gets stopped by a clump of grass or leaves or something — but a few keep rolling farther and farther. If you’re collecting eggs and you keep heading in the direction where you see the most of them, you’ll end up getting closer and closer to the Easter Bunny, because only a few eggs manage to roll really far from him, while more of them pile up closer to the source.
That’s chemotaxis: just like you’d get closer to the Easter Bunny by always moving in the direction where you see the most eggs, neutrophils get closer to the cells calling for help by always moving toward the highest concentration of chemokine molecules.
How Rosemary Modulates Immune Signals
Neutrophils are part of the innate immune system, and so are macrophages. Rosemary can inhibit macrophages’ production of both reactive oxygen species and the inflammatory cytokines TNF-α and IL-6 in vitro, specifically when these are elevated in response to lipopolysaccharides — molecules found in the cell walls of gram-negative bacteria (Francolino et al., 2023). Elevated IL-6 is associated with anxiety, and rosemary has been found effective at reducing anxiety (Nematolahi et al., 2018).
But the picture isn’t always “rosemary suppresses inflammatory cytokines.” Achour et al. (2022) found the opposite effect: participants who drank rosemary tea for ten days saw their TNF-α levels increase. Set against the Francolino findings, this suggests a modulatory effect rather than a purely suppressive one — and the study authors themselves seemed surprised by the increase, given that other research had shown TNF-α decreasing with rosemary. They point out this was a small study (22 participants) over just ten days, and it’s possible some participants had unusually low TNF-α at baseline, which would make an increase more likely to show up.
That possibility matters because TNF-α isn’t always something you’d want less of. Marucha et al. (2005) studied TNF-α in breast cancer patients and found that adequate — not minimal — TNF-α levels were important for a healthy immune response, since inflammation plays a role in killing cancer cells. Interestingly, patients who maintained greater social activity had higher TNF-α levels. Taken together, these studies raise an intriguing possibility: rosemary’s effect on TNF-α may depend on where someone’s levels start out — potentially raising it when it’s too low and lowering it when it’s too high.
The content of this blog is for educational purposes and is not intended as medical advice. Please work with a qualified healthcare provider for personalized guidance.
References
Achour, M., Ben Salem, I., Ferdousi, F., Nouira, M., Ben Fredj, M., Mtiraoui, A., Isoda, H., & Saguem, S. (2022). Rosemary tea consumption alters peripheral anxiety and depression biomarkers: A pilot study in limited healthy volunteers. Journal of the American Nutrition Association, 41(3), 240–249.
Francolino, R., Martino, M., Caputo, L., Amato, G., Chianese, G., Gargiulo, E., Formisano, C., Romano, B., Ercolano, G., Ianaro, A., De Martino, L., & De Feo, V. (2023). Phytochemical constituents and biological activity of wild and cultivated Rosmarinus officinalis hydroalcoholic extracts. Antioxidants, 12(8), 1633.
Marucha, P. T., Crespin, T. R., Shelby, R. A., & Andersen, B. L. (2005). TNF-α levels in cancer patients relate to social variables. Brain, Behavior & Immunity, 19(6), 521–525.
Nematolahi, P., Mehrabani, M., Karami-Mohajeri, S., & Dabaghzadeh, F. (2018). Effects of Rosmarinus officinalis L. on memory performance, anxiety, depression, and sleep quality in university students: A randomized clinical trial. Complementary Therapies in Clinical Practice, 30, 24–28.
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