The mechanisms behind the "farmhouse effect" - which indicates that children who grow up on a farm are less likely to suffer from allergies - are now examined.
Farmhouse effect in mice
There are indications that an immune system that is not kept busy by bacteria, viruses and worms, could overreact and cause allergies like hay-fever. Very clean environments are likely to cause this kind of “lazy” immune system.
To test the “farmhouse effect” – which indicates that children who grow up on a farm are less likely to suffer from allergies – researchers examined two groups of mice. One group was born and reared in a cowshed, the other in the lab and transferred to the shed after four weeks. It turned out that the second group was slightly less well protected and showed some allergic responses.
A comparison of cells and signalling substances in the immune system also shows that the reactions differ considerably. The immune defence of the farm-born mice was constantly activated but at the same time powerfully regulated by germs from the cowshed.
“The immune system evidently learns to moderate its response,”lead investigator Philippe Eigenmann from Geneva University Hospitals explains at the university’s website.
Moreover, they could show that the animals’ gut flora differed depending on their living conditions, and that the changes in gut flora and the immune system were many and varied. This variation keeps the immune system active and on edge, which is a reason why pro-biotics – with a single strain of germs – is less useful. The diversity is key.