Gut Bacteria Inject Proteins to Influence Immune System

Groundbreaking study reveals bacteria use 'syringe-like' structures to directly communicate with human cells.

Published on Feb. 16, 2026

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Researchers have discovered that many gut bacteria possess microscopic 'syringes' called Type III secretion systems (T3SS) that can inject bacterial proteins directly into human cells. This previously unrecorded communication mechanism offers a new understanding of the gut microbiome's role in health and disease, with implications for inflammatory conditions like Crohn's disease.

Why it matters

The finding that gut bacteria can directly influence the human immune system through protein delivery challenges the previous understanding that their impact was primarily through metabolite production. This opens new avenues for developing microbiome-based therapies that can modulate immune responses in a targeted manner.

The details

The research team mapped over 1,000 bacterial protein and human protein interactions, revealing that these injected bacterial effectors can impact central immune signaling pathways like NF-kB and MAP kinase. Patients with Crohn's disease showed a higher prevalence of genes encoding these bacterial effector proteins, suggesting a link between direct protein delivery and chronic inflammation.

  • The study was published on February 16, 2026.

The players

Professor Pascal Falter-Braun

Director of the Institute of Network Biology, who notes that the findings may reinforce the idea that Crohn's disease patients could benefit from 'gardening their microbiome' and suggests the research points to differing mechanisms driving ulcerative colitis versus Crohn's disease.

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What they’re saying

“This finding may reinforce the idea that Crohn's disease patients could benefit from 'gardening their microbiome' – reducing harmful bacteria and increasing beneficial ones.”

— Professor Pascal Falter-Braun, Director of the Institute of Network Biology

What’s next

Future research will focus on understanding the functional effects of these bacterial effectors in human cells, examining their influence on signaling pathways and cellular responses. More complex systems, such as disease models and human organoids, will be crucial for capturing the full physiological context.

The takeaway

This groundbreaking research reveals a previously unrecorded communication mechanism between gut bacteria and the human immune system, opening new avenues for developing targeted microbiome-based therapies to address inflammatory diseases.