Original Published Date: 
Thursday, November 18, 2021

Full article issued by Monash University.

An international team of researchers including ARC-supported researchers at Monash University have found molecular proof of how diet ultimately affects immunity through the gut microbiome. The findings offer a unifying explanation for the complex interplay between diet, gut microbiota and immune function.

The researchers pinpointed a microbial molecule in the human gut called B. fragilis that sets off an immune-signalling cascade triggered by the diet of its host.

The multistep pathway begins with B. fragilis taking up the branch-chained amino acids and then converting them into sugar-lipid molecules that ultimately induce natural killer T (NKT) cells to modulate an immune response.

Furthermore, the team found that B. fragilis alters the structure of the sugar-lipid molecules that it metabolizes and renders them better capable of binding to receptors on specific immune cells to reduce inflammation.

Using a structural biology approach, Professor Jamie Rossjohn, an ARC Laureate Fellow at the Monash Biomedicine Discovery Institute, was able to show how the lipid structure engages with and binds to antigen-presenting cells – the immune cells that give NKT cells the go-ahead to produce anti-inflammatory chemicals.

'This work offers a great example of trans-disciplinary discovery-based research aimed at answering a major question in biomedical sciences, namely how the immune system can be modulated by the interplay between diet and the microbiota,' Professor Rossjohn says.

The findings offer the hope that inflammatory diseases mediated by these NKT cells could one day be treated with inflammation-dampening microbial molecules made in the lab, the researchers said.

Photo credit: 

Image: artwork created by Dr Erica Tandori: Branching Out – branched chain fatty acids, B. Fragilis and Natural  Killer T Cell activation in the gut biota.