Allergy researchers study molecular processes in hyposensitisation to pollen
In allergen-specific immunotherapy, previously known as hyposensitisation, doctors inject patients with the substances that cause allergic reactions, such as pollen or mite allergen extracts. During first phase of the therapy, the dose is gradually increased and once a maintenance dose is reached, the patient continues to receive injections at that dosage over an extended period, which is usually an estimated three years. If the therapy is a success, there is lasting reduction in the intensity of allergic reactions.
It remains unclear what exactly happens in the body during these treatments. A team surrounding Dr. Adam Chaker, head of Allergy Outpatient Clinic at the Clinic and Polyclinic for Ear, Nose and Throat Medicine at the the TUM rechts der Isar University Hospital and Professor Carsten Schmidt-Weber, head of the Center for Allergies and the Environment (ZAUM) of TUM and the Helmholtz Zentrum München, has completed the first three-year investigation into the complex interplay of various cell types and substances of the human immune system.
Dr Chaker commented: “Our data show that the bodily processes during immunotherapy are far more complex than once believed. They involve cell types that have previously received very little attention in this context. In particular, we are convinced that regulatory B cells play a much more important role than we once thought”.
Allergy research has previously focused on the role of various types of T cells. However, according to this simplified model, pro-allergic T cells (Th2 and Th17 cells) heighten the allergic responses in the body when they encounter certain substances. By contrast, regulatory T cells (T regs) inhibit the response to an allergen.
“In the second treatment phase, the body’s immune system decides whether to continue launching all-out attacks on an allergen, resulting in hay fever, asthma or other allergic conditions, or whether the body will learn to tolerate the allergen,” Dr Chaker explained.
The ratios of pro-allergic T cells, T regs, and regulatory B-cells constantly change in that time. Over the course of the study, there were repeated shifts in which of the cell types was most numerous, also depending on pollen counts and other factors, with different types more prevalent at alternating times. It was only after three years that the ratios slowly stabilised.
In the patients who completed the treatment as planned, there were common factors that made it possible to forecast the success of the therapy at an early stage.
“We have patented this test. If we can develop it to the point where it can go into full production, we could save patients from going through expensive and time-consuming treatments with little chance of success. But in case of a positive test result, there are good reasons for seeing a three-year therapy through to the end. In the past, people have tended to give up before finishing.
“In addition, a better understanding of the molecular mechanisms could serve as the basis for more effective treatments. To do that, however, it will be necessary to confirm the results of the current study through additional investigations and find out more about the mechanisms involved”, Dr Chaker concluded.