We live in a world bustling with microbes—bacteria, viruses, and fungi are everywhere. But here’s the catch: it’s not as simple as “microbes come in, and we get sick.” In reality, our bodies establish a mutual relationship with most microbes, many of which are essential for our health. So, why do we sometimes get sick?
Our immune system is remarkably intelligent, but it relies on specific signals to decide when to act:
Stranger Signal: Microorganism-Associated Molecular Patterns (MAMPs) help your immune system recognize microbes. Think of them as a polite knock at the door—"Hey, I’m new here!” Without any signs of tissue damage or stress, your immune system typically tolerates these stranger signals, allowing for coexistence.
Danger Signal: Damage-Associated Molecular Patterns (DAMPs) act as a true alarm. When tissues are stressed or damaged, they alert your immune system: “This isn’t just a visitor—it’s trouble!” That’s when your immune defenses mobilize into action.
Why We Need Both Signals
Living in a clean world is important, but eliminating all microbes is neither possible nor desirable. Our bodies are built to coexist with the microbial world, fostering healthy relationships with beneficial microbes while remaining vigilant against harmful ones. Without danger signals, your immune system wouldn’t overreact to the microbial world—it learns to work with it instead.
This balance is crucial for health. It’s not about erasing all microbes; it’s about finding harmony with them. A clean world doesn’t mean a sterile one. Your immune system thrives on balance, adapting to the microbial world around you while standing ready to protect against genuine threats. Learning to live in harmony with microbes is the key to staying healthy in a world full of life.
Kroemer, G., Montégut, L., Kepp, O., & Zitvogel, L. (2024). The danger theory of immunity revisited. Nature Reviews Immunology, 24(12), 912–928. https://doi.org/10.1038/s41577-024-01102-9
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