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Background: Eosinophilic granulomatosis with polyangiitis (EGPA) is a systemic autoimmune disease underscored by vessel inflammation. Type 2 immune responses characterize its pathogenesis; indeed, therapies targeting interleukin-5, secreted by CD4 + T H 2 cells and sustaining the functions of eosinophils and perhaps B cells, ameliorate the disease. However, treated EGPA may relapse highlighting the plasticity of the disease-driving immune mechanisms.
Objectives: We aim to comprehensively explore the immune mechanisms underlying EGPA, with a focus on eosinophils and B cells. Specifically, we want to address:
How does immunometabolism underpin dysfunction of eosinophils and B cells in EGPA?
How does therapy of EGPA affect the metabolic requirements, epigenetic profile and ultimately function of eosinophils and B cells?
Methods: We are recruiting 10 EGPA patients, at onset and remission, and 10 healthy donors. We use fresh peripheral blood mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs) to assess the immune cell composition and perform immunometabolic phenotyping using spectral flow cytometry. To study the metabolic requirements of eosinophils and B cells, we purify the cells using magnetic sorting and we will perform mass spectrometry analysis. We also use eosinophils and B cells to perform single cell RNA sequencing and analyse their chromatin landscape via RELACS technique. Frozen PBMCs and PMNs are also stored for validation of our findings in functional settings.
Results: Besides the expected elevation of eosinophil counts, the blood of EGPA patients had a higher proportion of IgG4-expressing B cells as compared to healthy donors, in line with their association to autoimmunity. Moreover, EGPA patients showed metabolic alterations in the B cell compartment. Using TMRM as a dye to read out the activity of the mitochondrial electron transport chain, B cells of EGPA patients with active disease showed reduced staining with TMRM. This pattern could be observed across multiple B cell subsets, in particular in activated cells such as memory B cells and plasma cells. Further analysis are undergoing to address whether this metabolic phenotype is seen in other immune cells.
Conclusions: While preliminary, our results suggest that alterations in cellular metabolism may underscore the (dys)function of immune cells in EGPA. It is still to be addressed whether such changes are cause or consequence of the disease.
REFERENCES: NIL.
Acknowledgments: NIL.
Disclosure of Interests: Raquel Lorenzetti GSK, Christos Aronis: None declared, Barbara Dreo: None declared, Jens Thiel GSK, Matteo Villa GSK.