INTRODUCTION
Anaphylaxis is the most severe manifestation of allergic disorders being a systemic hypersensitivity life-threatening reaction that usually evolves rapidly [1;2]. Currently, 50-112 cases per 100.000 habitants are registered per year, but this incidence seems to be underestimated [3]. The plethora of features associated to anaphylaxis confers difficulties to its diagnosis, thus impairing the ability to treat adequately these severe reactions. The only marker currently used in clinical practice is the serum tryptase, however levels of this molecule are not altered in all cases [4;5]. High-throughput and systems biology analysis (SBA) implementation allow gaining knowledge on novel clues of action, aimed to improve patients´ management towards a personalized medicine for allergy treatment [6]. Different phenotypes and underlying anaphylactic endotypes have been described based on a few diagnostic biomarkers [7;8]. The current criteria to define anaphylaxis is clinical, however considering the pleiotropic features of the reactions, the approach to precision medicine evolves towards a larger knowledge of the etiopathogenesis. Mechanistically, anaphylactic reactions are established, but it is necessary to set up cellular and molecular processes beyond IgE, mast cells and tryptase [4;9;10]. Among the affected systems, cutaneous symptoms are the most frequent, but the respiratory and circulatory ones are relevant in the onset of severe anaphylactic reactions. The vessels stand out due to the increased vascular permeability and vasodilation that occurs during this pathological response, which promotes the development of anaphylactic shock [11]. The systemic nature of the anaphylactic reaction demands new approaches to improve diagnosis and molecular characterization.
Extracellular vesicles (EVs) is the generic term for a heterogeneous group of particles naturally released by most cell types, delimited by a lipid bilayer and that cannot replicate [12;13]. A growing body of evidence points to EVs as an efficient system to transfer targeted information to recipient cells playing an active role in cell-to-cell communication [14]. They carry molecular determinants from their origin including nucleic acids, proteins, lipids and others [15]. EVs biological functions are wide and include antigen presentation, angiogenesis, inflammation and coagulation. Importantly for the allergy field, recent findings identify exosomes as important in the progression of asthma [16;17]. Exosomes are the most known sub-family of EVs and have been deeply studied in immunity and cancer [18;19]. Mast cells, basophils and other members of the immune system secrete EVs creating a dynamic network that could be crucial for the anaphylactic response [20]. The soluble nature of EVs, their presence in all the biological fluids and their early detection in many different pathologies propose them as an economic and promising tool for diagnosis [21;22]. Even more, proteomic analysis of EVs has been recently proposed as a bona fide diagnosis method for some cancers [23]. EVs profiling and their role in human anaphylaxis has not been reported.
In this study, we have performed a quantitative proteomic signature of plasma circulating anaphylaxis-derived EVs and point to clarify their biological and functional properties. In addition, an in vitroevaluation of the endothelial barrier function has been carried out in response to these particles.