Artikel
Veränderungen der peripheren B-Zellkompartiment und des B-Zell-Klassenwechsels bei Patienten mit eosinophiler Granulomatose mit Polyangiitis
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Autoren
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Jens Thiel
- Klinik für Rheumatologie und Klinische Immunologie, Universitätsklinikum Freiburg, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Deutschland, Rheumatologie und Klinische Immunologie, Freiburg
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Marie Engesser
- Klinik für Rheumatologie und Klinische Immunologie, Universitätsklinikum Freiburg, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Deutschland, Rheumatologie und Klinische Immunologie, Freiburg
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Reinhard Voll
- Department of Rheumatology and Clinical Immunology, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg
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Arianna Troilo
- Klinik für Rheumatologie und Klinische Immunologie, Universitätsklinikum Freiburg, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Deutschland, Rheumatologie und Klinische Immunologie, Freiburg
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Raquel Lorenzetti
- Klinik für Rheumatologie und Klinische Immunologie, Universitätsklinikum Freiburg, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Deutschland, Rheumatologie und Klinische Immunologie, Freiburg
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Marta Rizzi
- Klinik für Rheumatologie und Klinische Immunologie, Universitätsklinikum Freiburg, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Deutschland, Rheumatologie und Klinische Immunologie, Freiburg
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Nils Venhoff
- Klinik für Rheumatologie und Klinische Immunologie, Universitätsklinikum Freiburg, Medizinische Fakultät, Albert-Ludwigs-Universität Freiburg, Deutschland, Rheumatologie und Klinische Immunologie, Freiburg
| Veröffentlicht: | 4. September 2017 |
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Gliederung
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Background: Eosinophilic granulomatosis with polyangiitis (EGPA) belongs to the group of ANCA associated vasculitides. While the combination of asthmatic symptoms and vasculitis characterize the disease clinically, eosinophilia and increased serum IgE concentrations are serologic hallmarks. The role of B lymphocytes in EGPA has not been defined so far, but therapeutic response to rituximab in EGPA points towards a role of B-cells in the pathogenesis of EGPA.
Methods: The objective of the work was to characterize the peripheral B cell compartment in patients with EGPA, and to analyze the in vivo potential of B lymphocytes to class-switch to IgE, and to assess in vitro the differentiation of naïve B cells to IgE-secreting plasmablasts.
B cell subpopulations were analyzed by staining PBMCs with fluorescent-labeled monoclonal antibodies against: CD27, CD20, CD38, IgD, IgG, IgA, IgE, CD21, and BAFF-R. For in vitro differentiation assays magnetically isolated B lymphocytes from EGPA patients and aged matched healthy controls were stimulated with CD40L and IL-21 and IL-4 in enriched Iscoves’ medium. Starting the culture with equal number of B cells, the absolute number of plasmablasts, and IgE class switched cells after 9 days was determined by counting the events in the CD27highCD38high gate or the IgG/A/D-IgE+ gate by flow cytometry. IgE secretion in the supernatant was measured by ELISA.
Results: 18 patients (8 females, median age 59 years) with EGPA diagnosed according to ACR and CHC-criteria were included into the study. 22% of patients were ANCA-positive. Immunosuppressive therapy was azathioprine in 11 patients, methotrexate in 3 patients, and leflunomid or mycophenolate in one patient each and two patients received no immunosuppressive treatment. 7 patients had a history of a prior cyclophosphamide therapy. Median lymphocyte count was normal (1.2x103/µl; normal range 1.1 to 3.2x103/µl) but peripheral B cell numbers were markedly diminished (37/µl, normal range: 100 – 500/µl). While the percentage of naïve B cells (53%) and marginal zone like B cells (10.5%) were within normal range, the percentage of class-switched memory B cells was high (28.2%). To assess the in vitro class switch capacity to IgE the number of IgE class-switched cells after 9 days of culture was determined. The in vitro IgE class-switch capacity of B cells from EGPA patients was significant greater than of healthy controls.
Conclusion: In the EGPA-patients we report we observed markedly diminished B-cells despite of normal lymphocyte counts. Within the B cell compartment, there was a shift towards later B cell maturation stages. The in vitro B-cell development to IgE class-switched cells was increased in EGPA-patients.
