“Numbers of autoimmune cases began to increase about 40 years ago in the west,” Lee told the Observer. “However, we are now
seeing some emerge in countries that never had such diseases before.
For example, the biggest recent increase in inflammatory bowel disease cases has been in the Middle East and east Asia. Before
that they had hardly seen the disease.”
Autoimmune diseases range from type 1 diabetes to rheumatoid arthritis, inflammatory bowel disease and multiple 
sclerosis. In each case, the immune system gets its wires crossed and turns on healthy tissue instead of infectious agents.
In the UK alone, at least 4 million people have developed such conditions, with some individuals suffering more than one. 
Internationally, it is now estimated that cases of autoimmune diseases are rising by between 3% and 9% a year. Most 
scientists believe environmental factors play a key role in this rise.
“Human genetics hasn’t altered over the past few decades,” said Lee, who was previously based at Cambridge University. “So
something must be changing in the outside world in a way that is increasing our predisposition to autoimmune disease.”
This idea was backed by Vinuesa, who was previously based at the Australian National University. She pointed to changes in diet 
that were occurring as more and more countries adopted western-style diets and people bought more fast food.
“Fast-food diets lack certain important ingredients, such as fibre, and evidence suggests this alteration affects a person’s 
microbiome – the collection of micro-organisms that we have in our gut and which play a key role in controlling various
bodily functions,” Vinuesa said.
“These changes in our microbiomes are then triggering autoimmune diseases, of which more than 100 types have now been
 discovered.”
Both scientists stressed that individual susceptibilities were involved in contracting such illnesses, ailments that also include
celiac disease as well as lupus, which triggers inflammation and swelling and can cause damage to various organs, including the
 heart.
“If you don’t have a certain genetic susceptibility, you won’t necessarily get an autoimmune disease, no matter how many Big
 Macs you eat,” said Vinuesa. “There is not a lot we can do to halt the global spread of fast-food franchises. So instead, we are
 trying to understand the fundamental genetic mechanisms that underpin autoimmune diseases and make some people 
susceptible but others not. We want to tackle the issue at that level.”
This task is possible thanks to the development of techniques that now allow scientists to pinpoint tiny DNA differences among 
large numbers of individuals. In this way, it is possible to identify common genetic patterns among those suffering from an 
autoimmune disease.
“Until very recently, we just didn’t have the tools to do that, but now we have this incredible power to sequence DNA on a large 
scale and that has changed everything,” said Lee. “When I started doing research, we knew about half a dozen DNA variants that
were involved in triggering inflammatory bowel disease. Now we know of more than 250.”
Lee also stressed that surging cases of autoimmune diseases across the world meant new treatments and drugs were now
 urgently needed more than ever before. “At present, there are no cures for autoimmune diseases, which usually develop in 
young people – while they are trying to complete their education, get their first job and have families,” he said.

来源：卫报