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Peanut Acclimation

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An experimental therapy to control peanut allergies may induce genetic changes in the immune system.


Transcript

An allergy therapy’s genetic impact. I’m Bob Hirshon and this is Science Update.

Stanford University immunologist Kari Nadeau and her colleagues are conducting trials of a therapy to control severe peanut allergies. They wanted to know why it works for some patients and not others.

They found that patients that ultimately responded to the treatment made more immune cells, called regulatory T cells, that kept the allergic response in check. Then they looked at the gene responsible for those regulatory T cells.

Nadeau:
And lo and behold, that was the one that you could see differences in, in those patients that were quote-unquote clinically immune tolerant versus those that were clinically non-tolerant.

The genes in the responsive patients had become more methylated—a chemical modification that alters a gene’s function without changing its underlying code. If confirmed, the findings could become a powerful new tool in allergy research. I’m Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

Severe allergies have increased dramatically over the last few decades (interestingly, almost entirely in developed countries), and peanut allergies are among the most common and severe. Some patients are so sensitive that even a small trace of peanut protein can trigger a life-threatening reaction. 

That's why some researchers, including Nadeau, are developing experimental therapies that may enable allergic people to tolerate small amounts of peanut protein, even if they can't eat it in large quantities. If successful, these patients could stay healthy by simply avoiding foods that contain peanuts as an ingredient, rather than foods that might simply have been contaminated with a little peanut dust during manufacturing or preparation.

The therapy they're developing is called “exposure therapy,” and it involves giving allergic people a liquid solution—under strict medical supervision—that contains increasing amounts of peanut protein, starting from an incredibly tiny amount. This therapy isn't safe for everyone, and doesn't always work, but in recent trials, it's enabled some patients to tolerate the amount of protein found in up to a tablespoon of peanut butter. 

The true test is whether the tolerance persists even after the patients stop getting the regular therapy. In Nadeau's study, 20 patients became peanut-tolerant after two years of exposure therapy. When the therapy stopped, they were re-tested after three months without peanut exposure. Of the 20, 13 patients maintained their tolerance, while seven had allergic reactions.

So why does this work in some patients but not others? Finding out could be a key to making this therapy work better. Nadeau's team observed that patients who stayed tolerant had more immune cells, called regulatory T cells, that actually controlled the allergic peanut reaction. 

Furthermore, the genes that produced those regulatory T cells were different. They had more methylation—the addition of a methyl group (R-CH3) to certain sites on the DNA sequence. Methylation changes the way a gene functions without altering the underlying code of the gene itself. And unlike the DNA sequence of a gene, which remains mostly fixed throughout an organism's life, the amount of methylation on a gene can change in response to environmental factors.

This phenomenon is part of an emerging field called epigenetics: the study of how genes can be influenced by the environment during an organism's lifetime. It was once thought that “genetic” was another way of saying “innate” or “unchangeable,” since an organism's genetic code is set. Now, with the emergence of epigenetics, we've learned that meaningful chemical modifications can be made to that basic genetic sequence, and that these can have a profound effect on gene activity. Exposure therapy may work by triggering epigenetic changes. If so, finding out why the changes take root in some patients and not others could make the therapy much more effective.

Now try and answer these questions:

  1. What is exposure therapy for allergies?
  2. What did the researchers learn about the effects of exposure therapy?
  3. What are epigenetic changes? How did these distinguish patients who responded to the therapy from those who didn't?
You may want to check out these related resources:
 

Asthma and Allergies: The Science Inside, part of a series that presents science information in an easy-to-read format, explains the basics of these respiratory conditions, their relationship to each other, prevention, treatments, and more.

For more about possible causes of the rise in asthma and allergies, see the Science Updates Anti-Asthma Bug and Antibiotics and Asthma.


Going Further


For Educators

In the lesson The Allergy Chronicles, students explore how the immune system functions in a variety of allergic reactions.

Asthma and Allergies: The Science Inside, part of a series that presents science information in an easy-to-read format, explains the basics of these respiratory conditions, their relationship to each other, prevention, treatments, and more.

For more about possible causes of the rise in asthma and allergies, see the Science Update lessons Anti-Asthma Bug and Antibiotics and Asthma.


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