THU0026 Organised b cells and plasma cells in the aorta of giant cell arteritis patients
Authors: J. Graver, M. Sandovici, E. Haacke, A. Boots, E. Brouwer
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Giant cell arteritis (GCA) is the most common type of systemic vasculitis. Currently, two forms of GCA are described: a cranial(C)-GCA and a systemic, large-vessel (LV)-GCA. LV-GCA frequently occurs without specific symptoms and late complications are aortic aneurysms or aortic rupture. Based on the analysis of temporal artery biopsies (TAB), GCA is postulated to start at the adventitial site and to be T cell-mediated. In the temporal artery infiltrates, T cells clearly outnumber B cells. Interestingly, we recently documented decreased numbers of B cells and elevated BAFF levels in newly diagnosed GCA patients prompting further research into the pathogenic role of B cells in GCA. Recent work in TAB of C-GCA patients demonstrated the presence of B cells and their organisation into artery tertiary lymphoid organs (ATLOs). <h3>Objectives</h3> Our objective was to investigated the presence and organisation of B cells in the aorta of patients with <h3>LV-GCA</h3> <h3>Methods</h3> Aorta tissue samples of 9 histologically-proven LV-GCA patients who underwent surgery due to an aortic aneurysm were studied by immunohistochemistry. Staining was performed with antibodies detecting CD20 (B cells), CD3 (T cells), CD21 (follicular dendritic cells (FDC)), PNAd (high endothelial venules (HEV)), bcl6 (germinal centre B cells), CD138 (plasma cells) and adipophilin (atherosclerotic plaque/macrophages). None of the patients received immunosuppressive treatment at the time of surgery. For comparison, 22 aorta samples from age- and sex-matched atherosclerosis patients with an aortic aneurysm were included. <h3>Results</h3> Aorta tissues of LV-GCA patients showed massive infiltration of B cells. The infiltrating B cells were mainly found in the adventitia and were frequently organised into high density B cell areas. In contrast to the temporal artery, B cells clearly outnumbered T cells in the aorta. ATLOs contained co-localised high density B cells and T cells, a FDC network, HEV and sometimes a germinal centre. ATLOs were observed in 77.8% of LV-GCA patients as opposed to only 36.4% of atherosclerosis patients. The number of ATLOs per patient was significantly higher in the LV-GCA group. Strikingly, ATLOs in aortas of LV-GCA patients contained more plasma cell niches and these niches also contained more plasma cells compared to aorta's of the atherosclerosis group. No association between the number of ATLOs and the number of atherosclerotic plaques was observed. <h3>Conclusions</h3> In conclusion, aorta tissues from patients with histologically-proven LV-GCA showed massive B cell infiltrates, predominantly located in the adventitia, that were organised into ATLOs. Moreover, these ATLO's frequently contained plasma cell survival niches. The predominance of organised B cells and plasma cells at the site of inflammation in LV-GCA suggests an involvement of B cell-mediated immune mechanisms in LV-GCA to be further explored. <h3>Disclosure of Interest</h3> None declared