Work described in this story was made possible in part by federal funding supported by taxpayers. At Harvard Medical School, the future of efforts like this - done in service to humanity - now hangs in the balance due to the government's decision to terminate large numbers of federally funded grants and contracts across Harvard University.
- By EKATERINA PESHEVA
One of the most captivating mysteries about the immune system is how it manages to keep its healthy equilibrium - staying on high alert and ready to react to harmful invaders or damaged cells, while remaining calm in the presence of innocent triggers such as food.
When it comes to gut immunity, this delicate balance might hinge on a tiny molecule on the surface of gut bacteria, according to a new Harvard Medical School-led study.
The research, done in mice, reveals that a small structural tweak in lipid A - a fatty-sugar molecule that sits on the outer surface of many gut bacteria - can determine whether immune cells in the colon go on the offensive or remain in a state of peaceful vigilance.
The work, supported in part by the Department of Defense and the National Institutes of Health and published in Cell, can inform new ways to prevent or treat inflammatory bowel diseases such as Crohn's, including the design of microbiome-targeted therapies that enhance gut immunity.
In most disease-causing bacteria, lipid A usually comes in a form with six fatty acid chains, which triggers a strong inflammatory response. The HMS-led team discovered that a rare four-chain version found in many bacteria that live in the intestine instead triggers gut cells to release a chemical that calms the immune system and helps sustain protective regulatory T cells (Tregs).