Across the world, food allergies are on the rise. One of the most important cells in studying this ailment are basophils, which activate inflammation and other allergic responses such as rashes and anaphylaxis. But basophils are exceedingly rare in a typical vial of blood, composing 1% or less of all white blood cells. In order to advance the science of food allergies – and to learn more about these elusive cells – engineers and clinicians at Stanford University have focused their attention on a way to isolate basophils.

Illustration of a basophil among red blood cells. (Image credit: Getty Images)

In a paper published in Lab on a Chip, the researchers outline a microfluidic system that isolates allergen-reactive basophils from blood samples. “Our long-term goal is to figure out how to design a better food allergy test that’s safer and more accurate,” said Sindy Tang, an associate professor of mechanical engineering and senior author of the paper. “We identified the basophil activation test as the most promising one given all the data from our clinical collaborators and labs throughout the world. But the current workflow is not amenable to widespread clinical use.”

Scientists have shown that a test that’s been around for more than 10 years, the basophil activation test, is a lot more accurate than other allergy tests – like a skin prick test or traditional blood test – but it’s currently only used in research settings.

Perfecting this test is a priority for some clinician-scientists like Stephen Galli, the Mary Hewitt Loveless, MD, Professor in the School of Medicine and co-author of the study, who says that this is the future of allergy testing – avoiding the discomfort and potential of serious adverse reactions in patients while also improving the chances of useful results.

“Of all patients with antibodies that might mediate true allergic reactions against a particular allergen, only about half of them actually show clinical reactivity to that allergen,” said Galli. “Using their basophils, 95% or more of patients with some clinically significant allergies can be identified.”

Purity through magnetic sifting

Currently, the basophil activation test requires a cumbersome laboratory procedure. The test these researchers envision could produce results faster with a comparatively hands-off approach that could enable clinical use. Isolating basophils from a small volume of blood is one critical aspect of their approach.

Beginning with a sample of whole blood, the researchers use a combination of size-based sorting to remove red blood cells before introducing a couple of special additives to the white blood cells. “We use an antibody cocktail, which targets non-basophils. And then magnetic nanoparticles bind to those antibodies,” said Nicolas Castaño, a PhD student and lead author of the paper.