Asthma and allergies are increasingly common in the U.S. and affect millions of people young and old. While many medications are available to combat the effects of these allergic conditions, gaps still remain in understanding how they develop and what might cure or prevent them. Now new research has uncovered part of why it is that growing up on a farm can help protect against allergies and asthma and the findings may help unlock new treatments for these bothersome and potentially deadly illnesses.
Where do allergies come from?
If you suffer from seasonal allergies, you’ve probably learned about the relationship between pollen levels outside and the misery of itching eyes and a running nose. While it might seem different to other types of allergies and asthma, the underlying cause is very similar. In almost all cases of allergy, the immune system of the body is hypersensitive to certain particles in the environment. Normally, the immune system will learn which particles in the environment are harmful and which are not so that the immune system only fights to protect our body from an invader when it’s really necessary.
For reasons that still aren’t clear, the immune system in people with allergies draws the line between friend and enemy too far into the enemy side. It attacks many harmless things we encounter everyday and is triggered more easily by insults from the environment. In asthma, for example, the airways of the lungs are much more easily irritated than the lungs of those without asthma. Pollen, dust mites, or even just cold air can set off inflammation in the airways, which then leads to breathing troubles.
How is farm living related to allergies?
Decades ago, researchers observed that people who grow up on farms are much less likely to have asthma and other allergy-related diseases. Several studies have indicated that toxins made by bacteria and present in the air and dirt on farms but not in cities may play a role. Many have hypothesized that the sterilization and killing of environmental bacteria in city settings could be behind the higher levels of allergies in those locations. This hypothesis is known as the “hygiene hypothesis.” The problem was that many other studies have found genetics to be important in the development of allergies and many wondered how environment and genes interacted when it came to allergies. This study helped to bridge that gap.
How did these researchers conduct their study?
The researchers used several different experiments to get a hold on how farm dust might relate to allergies.
In their first study, they exposed mice to a commonly known bacterial toxin called LPS every other day for two weeks. They then exposed them to dust mite particles, which are known to trigger the allergic reaction that leads to asthma. Exposing mice to the toxin led to a smaller immune response to dust mites and fewer asthmatic symptoms compared to mice that weren’t exposed. In following the reaction on a molecular level, the researchers found that dust mite and toxin exposure led to some genetic changes in how the body uses a protein called A20.
In the next experiment, the researchers bred a group of mice that didn’t have this A20 protein to see how vital its role was. They then performed a similar experiment to the first and found that when mice couldn’t make the A20 protein, the LPS toxin no longer prevented asthma symptoms or immune response after dust mite exposure. This showed the team that A20 was important for whether or not allergies were developing in response to the environment.
But the researchers weren’t satisfied with just testing LPS since many other bacterial components are present in farm dust. They repeated the previous two experiments, but used dust taken directly from a farm instead of LPS. They found the same effects as before: farm dust lowered asthma symptoms and immune activity, but only when mice could make A20.
The final step was to see how this might apply to people. The group gathered tissue samples from the lungs of people with and without asthma. They exposed those samples to dust mite allergens and looked at how they responded. Sure enough, samples from people with asthma had low levels of A20 and responded with panic to the dust mites. But people with normal lungs had plenty of A20 around and didn’t respond as vigorously.
The final step was looking at whether the levels of the protein A20 might be having a big effect in human populations. The researchers used past genetic and allergy data to see if changes in the A20 gene were connected to asthma and allergy symptoms. When they crunched the numbers, they found a link. This showed that avoiding asthma and allergies depends both on having the right genes and being exposed to the right environment.
What does this mean for me?
This study is one of the first to show such a conclusive and thoroughly tested relationship between genetics, the environment, and allergies. The research could lead to new treatments for people with allergies and asthma as well as better ways to prevent them from developing in the future. The study also confirms that when it comes to allergies, absolute avoidance of dirt and dust may not be the best thing for developing immune systems.