Extracellular Vesicles from Monocyte-Derived Dendritic Cells Modulate Lymphocyte and Eosinophil Responses in Cow’s Milk Allergy

Cow's milk allergy (CMA) is characterized by an exaggerated immune response where dendritic cells (DCs) play a crucial role. Additionally, extracellular vesicles (EVs) can be released by immune cells, modulating this allergic response. Moreover, eosinophils also contribute to tissue damage and perpetuate inflammation in allergic reactions. Therefore, the aim of this work was to study the role of EVs from monocyte-derived dendritic cells (moDCs) on eosinophil and lymphocytes in CMA. Sixteen infants with IgE-mediated cow's milk allergy (CMAIE) and three non-allergic controls were recruited. Peripheral blood monocytes were purified and differentiated to moDCs. EVs were obtained from the culture supernatant by ultracentrifugation and characterized by nanoparticle tracking analysis and Western blot. Interaction among EVs, eosinophils and peripheral blood mononuclear cells (PBMCs) were analyzed with confocal microscopy. Additionally, these cells were incubated with EVs to assess lymphocyte proliferation, as well as eosinophil migration and reactive oxygen species (ROS) production by flow cytometry. Moreover, multiplex analysis was performed to evaluate the cytokines released by PBMCs following stimulation with EVs. Proteins characteristic of EVs were identified (CD9, CD63, CD81 and Alix). Furthermore, the size of the nanovesicles was ~185 nm, which is consistent with previously published reports. Confocal microscopy revealed that EVs internalized and localized in the cytoplasm of eosinophils, while in PBMCs, EVs were located in the perinuclear region. A proliferation assay revealed an increase in the proliferation of Th1 and Th2 lymphocytes, with higher levels of IL-4. Moreover, EVs were able to significantly increase eosinophil ROS production and migration. However, these effects were not observed after stimulation with EVs from non-allergic controls. This exploratory study shows that EVs from the moDCs of children with CMAIE could induce chemotactic and stimulatory functions on eosinophils and lymphocytes, which could perpetuate inflammation and contribute to tissue damage in this type of allergy.