A new type of immune cell may cause lifelong allergies
The cells’ identification could lead to new allergy treatments or cures
A newly discovered subset of memory cells could one day be used to learn whether a person's allergy is likely to last or could disappear with time or treatment.
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Allergy sufferers may one day be able to erase the source of their sniffles, itchy skin and swelling. A newfound subtype of immune cells seems to underlie long-lasting allergies. The finding could lead to new ways to diagnose, treat or even cure allergies.
Memory B cells are important for long-lasting protection against infectious diseases. The new cells are called type 2 memory B cells or MBC2s. This subset holds the memory of proteins that cause allergies. And these cells are primed to make the type of antibodies that trigger classic allergy symptoms.
Two separate groups of researchers described these cells February 7 in Science Translational Medicine.
Allergies happen when the immune system reacts to harmless things, such as pollen, peanuts and pet dander. Some immune cells release a type of antibody called IgE to fight the mistaken foe. Usually, IgE antibodies battle real threats, such as parasitic worms.
In the United States, about one-third of adults and one-quarter of all children have allergies. For many, their symptoms are just seasonal sniffles. But in some people, insect stings or certain foods can cause life-threatening allergic reactions. Some allergies disappear over time or with treatment. Others last a lifetime.
For decades, scientists have been searching for the source of those long-lived allergies.
Memory B cells help the body remember vaccinations and natural infections. Recently, researchers began to suspect they might be linked to allergies, too. These memory B cells produce antibodies known as IgG. These ward off viral and bacterial infections. They can also neutralize some toxins. It wasn’t clear how the cells might switch to making IgE antibodies instead.
To explore this, both research teams studied the immune cells of people with allergies and some without. One group worked with adults, the other with kids. The two studies also looked at different types of allergies.
How cells remember allergens
Joshua Koenig helped lead one of the studies. He’s an immunologist at McMaster University. That’s in Hamilton, Ontario, in Canada. His team of scientists examined more than 90,000 memory B cells. The cells came from six adults with birch allergies, four allergic to dust mites and five people with no allergies.
The team focused on the cells’ RNA. RNA is like a blueprint that cells use to make proteins. Based on RNA, some of the memory B cells appeared ready to make the antibodies and other proteins involved in an allergic response. The researchers called this subset of cells MBC2s.
In another experiment, they used a peanut protein as bait to fish for memory B cells. In people with peanut allergies, the memory B cells increased in number and made IgE antibodies against peanuts. The team found the same type of cells in people with birch and dust-mite allergies.
The connection is clear, Koenig says. “You find the cells present in the allergic people. It’s not present in the nonallergic people,” he says. “These cells are the ones that are making these antibodies, and that’s how this memory is being held.”
A quick switch
The second research group looked at kids with peanut allergies. It was led by immunologist Maria Curotto de Lafaille. She works at the Icahn School of Medicine at Mount Sinai in New York City. Levels of memory B cells were higher in 58 children allergic to peanuts than in the 13 kids without allergies. The cells were similar to those described by Koenig’s group. Lafaille’s team called them type 2 memory B cells.
It’s clear that both groups have found the same cells, says Cecilia Berin. She’s an allergist and immunologist who did not take part in the new studies. She works at Northwestern University Feinberg School of Medicine. That’s in Chicago, Ill. There are “very consistent findings between the two groups,” she says.
The cells are poised to switch from making protective IgG antibodies to allergy-causing IgE antibodies, Lafaille’s team found. Even before the switch, the cells were making RNA for IgE but didn’t produce the protein. Making that RNA enables the cells to switch the type of antibodies they make when they encounter the allergen.
“They are one step ahead of other cells to respond and to switch,” Lafaille concludes.
The signal to switch partially depends on a protein called JAK, her group discovered. That makes JAK a potential target to treat or prevent allergies, Lafaille says. If you stop the “switch” signal, you might prevent the memory cells from making IgE. Other researchers at Mount Sinai are now testing a JAK-blocking drug in people with food allergies.
Lafaille also hopes these memory cells can be used to learn whether a patient’s allergy is likely to last or disappear with time or treatment.
Finally knowing why some allergies persist might help scientists find other ways to target allergy cells, Berin says. “You could potentially get rid of not only your peanut allergy but also all of your allergies.”
