The influence of <i>Aspergillus fumigatus</i> micromycetes on immune response regulation in patients with asthma

Abstract

Introduction. Aspergillus fumigatus is able not only to sensitize patients with atopy, but also to colonize the respiratory tract, remaining a constant source of allergens due to the small spore size and thermal tolerance. Currently, the role of micromycetes in the immunopathogenesis of asthma has been poorly studied. The objective was to evaluate the features of the immune response regulation in patients with allergic bronchopulmonary aspergillosis (ABPA) or asthma with sensitization to A. fumigatus. Materials and methods. There were enrolled 15 patients with ABPA, 10 patients with asthma with sensitization to A. fumigatus, 16 patients with asthma without sensitization to A. fumigatus. The control group consisted of 16 apparently healthy volunteers. All patients underwent a clinical and functional examination. The subpopulations of blood lymphocytes were assessed by flow cytometry. The A. fumigatus allergen was added to peripheral blood samples to evaluate the production of IFN, IL-10 and IL-13. The serum cytokine levels in cell culture supernatants, as well as total IgE, A. fumigatus-specific IgE (sIgE) as well as thymus and activation-regulated chemokine (TARC) level were measured by enzyme-linked immunosorbent assay. Results. Significantly higher serum levels of total IgE, A. fumigatus-specific sIgE and TARC were found in patients with ABPA and asthma with sensitization to A. fumigatus compared to patients with asthma without sensitization to A. fumigatus. The results of lymphocyte immunophenotyping revealed significant excess of memory Th2 cells and T-regulatory cells in all patients with asthma compared to the control group. The count of Tfh2 was higher but memory Th17.1 cells were lower in patients with sensitization to A. fumigatus compared to those of apparently healthy volunteers. Patients with ABPA had significantly higher count of memory Th2 cells and TARC level compared to patients with asthma sensitized to A. fumigatus. The increased activity of memory Th2 cells is confirmed by increased secretion of IL-13 and IL-10 following along with decreased IFN production in response to specific fungal allergen stimulation of blood cells compared to the patients with asthma and the control group. A positive correlation was revealed between the count of memory Th2 cells and the levels of sIgE, IgE, TARC, a negative correlation with FEV1. Conclusion. Thus, exposure to A. fumigatus significantly enhances the activity of memory Th2 cells in patients with asthma which can lead to severe disease course and development of allergic bronchopulmonary aspergillosis. The features of the immune response identified dictate a need for a personalized approach to choose therapeutic tactics in such patients.