Non-proliferating plasma cells detected in the salivary glands and bone marrow of autoimmune NOD.B10.H2b mice, a model for primary Sjögren’s syndrome

<p>Autoantibody secreting plasma cells (PCs) are essential contributors in the development of autoimmune conditions such as primary Sjögren’s syndrome (pSS). Particularly, the long-lived PC subset residing in the bone marrow has shown to continuously produce autoantibodies, whilst remaining unaffected by immunosuppressive treatment. We have previously shown accumulation of potentially long-lived PCs in chronically inflamed salivary glands of pSS patients. In this study, we aimed to characterise the PC compartment in the salivary glands (the target organ for pSS) and bone marrow before the onset of the murine pSS like disease versus advanced diseases progression. Bromodeoxyuridine (BrdU) was incorporated to distinguish the long-lived PCs. Double immunohistochemical staining and immunofluorescence were then conducted on submandibular gland and bone marrow sections from 8- and 40-week-old mice to identify BrdU and CD138. BrdU⁺ cells were detected in the submandibular glands of 8-week-old mice, and observed within all focal infiltrates by 40 weeks of age. Most CD138⁺ PCs were however BrdU⁻ and located predominantly on the periphery of these infiltrates. This observation was verified through immunofluorescence. A comparable staining pattern was observed in the bone marrow of 8- and 40-week-old NOD.B10.H2b mice, where some of the CD138⁺ cells also expressed BrdU. Interestingly, megakaryocytes in the bone marrow of NOD.B10.H2b mice were detected in close proximity to CD138⁺ cells, illustrating a possible presence of PC survival niches. Our results demonstrate the presence and accumulation of potentially long-lived PCs in NOD.B10.H2b mice as the disease advances.</p

Signalling pathways identified in salivary glands from primary Sjögren’s syndrome patients reveal enhanced adipose tissue development

<p>A characteristic feature of primary Sjögren’s syndrome (pSS) is the destruction of salivary and lacrimal glands mediated by mononuclear cell infiltration. Adipocytes can also occupy a large portion of the salivary gland (SG) tissue area, although little is known about their significance in pSS. We have previously investigated adipose tissue infiltration in SG biopsies from pSS patients and non-SS sicca controls. Our findings indicated the distinct incidence of adipose tissue replacement in pSS patients, where adipocytes were detected in interleukin (IL) 6 rich regions. We now aimed to examine the development of adipocytes in the SG microenvironment, and delineate their possible involvement in immune reactions. A microarray analysis was performed on SG from 6 pSS patients and 6 non-SS controls, where the expression levels of genes involved in adipose tissue development, inflammatory responses, and lymphoma development were assessed. Real-time PCR was carried out on SG from 14 pSS patients and 15 non-SS controls to account for IL6, IL10, and IL17 mRNA levels. Immunohistochemical staining of frozen SG tissue using IL17 was also conducted. Our results indicate signalling pathways identified in SG of pSS patients displayed genes leading to prominent adipose tissue development and reduced mitochondrial fatty acid beta-oxidation (<i>ARID5B</i>, <i>OXCT1</i>, <i>BDH1</i>, <i>SOX8</i>, <i>HMGCS2</i>, <i>FTO</i>, <i>ECHS1</i>, <i>PCCA</i>, <i>ACADL</i> and <i>ACADVL</i>), inflammatory responses (<i>IL1R1, IL7R, IL10RA, IL15, IL18RAP, CCL2, CCL5, CCL22, CXCR6, CD14</i>, and <i>CD48</i>), and lymphoma development via JAK-STAT signalling (<i>STAT2, TYK2, EBI3, FAS, TNFRSF1B, MAP3K8, HMOX1, LTB, TNF, STAT1,</i> and <i>BAK1</i>). Genes involved in interferon production and signalling were also detected (<i>IRF1, IRF9,</i> and <i>IRF7</i>), in addition to <i>IL6, IL10</i>, and <i>IL17</i>. Higher mRNA levels of IL6, IL17 and IL10 were observed in the SG of pSS patients compared to controls. Moreover, IL17 positive cells were detected mostly interstitially in the SG and around adipocytes, also within the focal infiltrates. In conclusion, adipocyte development seems to be more prominent in the SG of pSS patients, where adipose tissue replacement is also evident. Whether this is due to disease progression, or the repair process, remains to be investigated. Detection of IL17 positive adipocytes in the target organ suggests their involvement in immune reactions.</p