New Link Between Autoimmune Diseases and a Gut Bacterium

Queen’s University researchers have, for the first time, found a specific microbe in the gut that pumps out protein molecules that mimic a human protein, causing the human defence system to turn on its own cells by mistake.

The culprit in this case is called Bacteroides fragilis, a bacterium that normally lives in the human gut. The Queen’s team has shown that this bacterium produces a human-like protein that could trigger autoimmune diseases, such as rheumatoid arthritis.  This human protein is called ‘ubiquitin’ and is needed for all the normal cell processes in our bodies.

The study, recently published in the British Society for Immunology Journal Clinical and Experimental Immunology  is a significant discovery.  “Mimic proteins” fool our immune defence system into reacting with our own bodies, resulting in autoimmune disease, a condition in which your immune system mistakenly attacks the body.

Professor Sheila Patrick, Professor Emeritus at Queen’s University explained: 

“When we mapped the genome of Bacteroides fragilis a few years ago we were astonished to discover a human-like gene not present in any other bacteria.  The protein produced from this gene is nearly the same shape as a protein in almost every human cell.

“When we discovered that Bacteroides fragilis produces lots of this mimic protein we were very excited. No other bacteria produced a mimic of human ubiquitin and this one lives in our gut. We immediately wondered if it might be linked with autoimmune diseases such as lupus. It has been known since the 1990s that some people with autoimmune diseases have antibodies that target their own human ubiquitin, but we don’t know why this happens. So we decided to see if people also had antibodies that target the Bacteroides fragilis version of ubiquitin.”

Full article at  Queen's University Belfast