Fine sorting

The frequency of food allergies is at a peak all over the world. One of the most important cell types in the development of this condition are basophils, which activate inflammation and other reactions to allergens, from rash to shock. But basophils are extremely rare: in a normal blood sample, they make up less than 1% of all white blood cells. In order to study food allergies more deeply and learn more about this elusive cell, Stanford University engineers and clinicians focused their attention on basophil isolation methods.

The basophil activation test, which has been in existence for more than 10 years, has proved to be the most promising in the diagnosis of food allergies in various laboratories around the world. According to approximate estimates, of all patients with antibodies that can mediate true reactions to a certain allergen, only 50% actually show clinical reactivity to it. Using basophils, it is possible to identify patients with clinically significant allergies with 95% accuracy.

But the existing basophil activation test is not amenable to wide clinical dissemination and is currently used only for research purposes. Improving this test was a priority goal of Stanford researchers. In an article published in the journal Lab on a Chip, they described a microfluidic system that quickly isolates allergen-reactive basophils from blood samples.

Magnetic Sieve

Currently, the basophil activation test requires cumbersome laboratory equipment. The modification proposed by the researchers can lead to faster results with a relatively easy approach, which will allow it to be used in clinical settings. Isolation of basophils from a small volume of blood is one of the most important aspects of the new approach.

Starting with a whole blood sample, researchers use size sorting to remove red blood cells, and then inject several special additives to white blood cells – a cocktail of antibodies that target all cells except basophils, and magnetic nanoparticles that bind to these antibodies.

Then, to isolate the basophils, the researchers pass the cells through a device that generates a magnetic field that attracts and immobilizes everything that is not a basophil. The strength of the magnetic field gradually increases, and at the outlet the liquid contains pure basophils.

Improving the test

The key factor in the development of the device was time. It is very important to isolate living cells quickly: blood cells have greater integrity the less time they spend outside the body, and this increases the accuracy of tests.

Quick sorting in 10 minutes, which the researchers have achieved, also increases the availability of tests for widespread use. The logistics of delivering blood samples from hospitals to treatment centers can reduce the likelihood that doctors will request tests. The ability to sort in clinics and diagnostic laboratories will help introduce a range of tests called immune functional assays, which doctors use to evaluate specific treatments at the cellular level and which require other types of white blood cells, not just basophils.

The authors intend to further improve the basophil activation test, since the microfluidic sorting system is an intermediate process. In order to completely update the method, blood collection and activation measurement must be similarly optimized. In the future, they hope to develop a fully automated, miniaturized, fast and standardized test that will become available to clinicians diagnosing or controlling food allergies.

Article by N.Castaño et al. Exponential magnetophoretic gradient for the direct isolation of basophils from whole blood in a microfluidic system is published in the journal Lab on a Chip.

Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru Based on Stanford University: In less than 10 minutes, Stanford researchers isolate the rarest white blood cells.