Warning: Germs can be good for you

27 Jun 2016

There has been a sharp increase in autoimmune diseases in the developed world in the past half century, and research points to the fact that this could be triggered by not enough exposure to certain infections as a young child.

Conditions such as type 1 diabetes and celiac disease are believed to be gene related, but the current rate at which the number of people affected by these autoimmune diseases is growing is too rapid to be attributed to changes in the gene pool.

Hygiend hypothesis

A study published in Cell journal tested the hygiene hypothesis – that a lack of early childhood exposure to infectious agents, symbiotic microorganisms (such as the gut flora or probiotics), and parasites increases susceptibility to allergic diseases by suppressing the natural development of the immune system.

The research tracked the gut microbiome development in 222 infants from birth until three in Northern Europe, where early-onset autoimmune diseases are common in Finland and Estonia but are less prevalent in Russia.

Findings

“We found that Bacteroides species are lowly abundant in Russians, but dominate in Finnish and Estonian infants. Therefore, their lipopolysaccharide (LPS) exposures arose primarily from Bacteroides rather than from Escherichia coli, which is a potent innate immune activator.”

“We show that Bacteroides LPS is structurally distinct from E. coli LPS and inhibits innate immune signalling and endotoxin tolerance; furthermore, unlike LPS from E. coli, B. dorei LPS does not decrease incidence of autoimmune diabetes in non-obese diabetic mice. Early colonisation by immunologically silencing microbiota may thus preclude aspects of immune education,” the study says.

True of other diseases

Alberto Ascherio, professor of epidemiology and nutrition at Harvard TH Chan School of Public Health, says in an article that this is also true with exposure to the Epstein-Barr virus, which causes multiple sclerosis (MS).

He says that childhood Epstein-Barr infection, common in the developing world, lowers MS risk, while acquiring it as an adolescent or adult, when it causes mononucleosis, can more than double it.