Mast cell test simplifies the diagnosis of food allergies

Researchers at the University of Bern and Bern University Hospital have developed a test to simplify the diagnosis of allergies, confirming its effectiveness in clinical samples from children and adolescents suffering from a peanut allergy. Their results, published in the journal Allergy, could fundamentally improve the clinical diagnosis of allergies in future.

The oral food challenge test, in which people consume an allergen (such as peanut extract) under supervision to test the allergic reaction, is still considered the gold standard in diagnosis; however, this method is complex and carries health risks. The allergen skin prick test and blood test are meanwhile not very accurate, which can lead to misdiagnoses and unnecessary food avoidance. An alternative test, developed by a team led by Bern’s Prof Dr Alexander Eggel and Prof Dr Thomas Kaufmann, mimics the allergic reaction in a test tube and thus offers an attractive alternative to standard tests.

“The most common food allergies are type I allergies; they develop when the body produces immunoglobulin E (IgE) antibodies in response to substances that are actually harmless,” Eggel said. These antibodies bind to specific receptors on the mast cells, which are immune cells that play an important role in allergic reactions and inflammation. They are mainly located in the tissue — for example, in the intestinal mucosa — and are prepared for and sensitised to the allergen by binding to the antibodies. Upon renewed contact with the allergen, it binds directly to the mast cells loaded with antibodies, activating them and triggering an allergic reaction.

Eggel explained, “In the Hoxb8 mast cell activation test (Hoxb8 MAT), which we developed, mast cells grown in the laboratory are brought into contact with blood serum from allergic patients. The mast cells bind the IgE antibodies from the serum and are sensitised by them. We can then stimulate the mast cells with different amounts of the allergens to be tested.” Quantifying the activated mast cells suggests how allergic a patient is to the allergen tested without needing to consume the food.

The new study used serum samples from a total of 112 children and adolescents who had already participated in a study in Canada and for whom clear diagnostic data on their peanut allergy status were available. The mast cells cultured in the laboratory were sensitised with their serum and then stimulated with peanut extract.

“The cell-based test was easy to carry out and worked perfectly,” Kaufmann said. “All samples were measured within two days, which was very fast.”

The results showed that a large number of sera from allergic patients exhibited allergen dose-dependent activation, while almost all samples from the non-allergic control subjects did not activate the mast cells. According to Eggel, “An exceptionally high diagnostic accuracy of 95% could be calculated from these data.”

In addition, the data measured in the study were analysed in direct comparison with other diagnostic methods established at the hospital. It was found that the Hoxb8 MAT test had significantly higher accuracy than the standard measurement of allergen-specific IgE antibodies in the blood or the frequently used skin test.

“Comparison with other clinical tests was crucial to determine which of them reflected the patients’ allergic reaction best,” Kaufmann said. “The new mast cell activation test has the advantage that it is functional and therefore incorporates many parameters that are important for triggering the allergy.

“The new test is also based on stable blood serum, which can be drawn using simple blood sampling and then stored in the freezer. This eliminates the challenging logistical obstacles that arise with other methods.” The study also showed that the Hoxb8 MAT test leads to less false negative results.

“What has been shown in this study on the diagnosis of peanut allergies can also be applied to other allergies in a simple way,” Eggel concluded. “The technology is a perfect example of how basic research from the University of Bern can be brought to the clinical practice, and might ultimately simplify life for patients and physicians.”

Image credit: iStock.com/Mypurgatoryyears