Crosstalk & immunity
In plain language
Few things affect people — and teams — as directly as recurring infections and persistent fatigue. One person catches every cold, another stays fit the whole season. Often the key lies not in the lungs or the blood alone, but in a much broader system: the conversation between your microbiome and your immune system. Around 70% of your immune cells reside in your gut, where they are continuously trained by your gut flora. If that dialogue runs smoothly, your defences respond in a targeted way and you recover swiftly. If the flora goes out of balance, your immune system can become overactive (more inflammation) or, conversely, respond more slowly (less defence). That explains why resistance is so personal — and why you can understand and strengthen it instead of waiting until you fall ill.
The science behind
The microbiome steers the immune balance. A central axis is the ratio between regulatory T cells (Treg, which dampen inflammation) and Th17 cells (which drive inflammation). Short-chain fatty acids and tryptophan metabolites — products of gut bacteria — help adjust that balance. If it tips towards Th17, the chance of overactive inflammation and even autoimmune processes increases; if it stays in balance, the defences work in a targeted way. Dysbiosis can therefore feed both an increased susceptibility to infections and a persistent low-grade inflammation.
Stress too acts on this crosstalk. Stress changes the composition of the microbiome and, via the gut–immune dialogue, can accelerate autoimmune processes. Conversely, research shows that pre-, pro- and synbiotics can strengthen the gut–immune crosstalk and thereby raise resistance to infections. The common thread is that resistance does not reside in one organ, but arises from a network of signals between gut, metabolites and immune cells.
Why one person is more resilient than another is co-metabolic: it depends on the interplay between genes, microbiome, metabolites and lifestyle together. Gene variants colour the predisposition in the background, but the whole determines how your defences behave — and that makes resilience measurable and supportable. This reading is supportive and observational — not a medical diagnosis.
Illustration & CosmoTalks
How your body adapts under pressure — five episodes about energy and adaptation.
- S6·E1 — Not more energy, but handling energy more cleverly
- S6·E2 — Mitochondria and microbes: the engine behind your day
- S6·E3 — Where energy leaks away: inflammation and stress
- S6·E4 — Adaptation in shift work and under load
- S6·E5 — Resilience as a trainable trait
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My InnerSelfie
Map your immune resilience: DNA, microbiome and metabolites together, translated into clear signals about susceptibility and inflammatory tone.
Discover My InnerSelfie →My Key Nutrients
Support your resistance from within: fibre-rich, SCFA-friendly nutrition and targeted biotics tuned to your co-metabolism.
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Discover CosmoPulse →The books · HOST · FORMULA · EDGE
The common thread of this science, from insight to everyday application, by Petra Van Gucht.
See the books →Scientific references
• Habiballah DN., et al. (2025) — Immune metabolic restoration via microbiota. Front Immunol.
• Fermin D., et al. (2024) — Pre-, pro- and synbiotics in the gut–organ axis. Cureus.
• Van Gucht P. — FORMULA (COSMO trilogy): resistance as an interplay of human and microbiome.
Frequently asked questions
- What is crosstalk and immunity?
- The ongoing dialogue between your gut microbiome and your immune system. Because a large part of your immune cells sits in the gut, that dialogue helps steer your resistance and resilience.
- Is it true that 70% of my immune cells are in the gut?
- Yes — a large part of the immune system is located in and around the gut, where it is continuously trained by the gut flora.
- What is the Treg/Th17 balance?
- The ratio between anti-inflammatory regulatory T cells (Treg) and pro-inflammatory Th17 cells. Microbial metabolites help steer that balance.
- Can I strengthen my resistance?
- Often you can, through nutrition, lifestyle and targeted biotics tuned to your profile. This is supportive and observational, not a medical diagnosis.
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