Vascular endothelial growth factor (VEGF) is implicated in the peritoneal membrane remodeling that limits ultrafiltration in patients on peritoneal dialysis (PD). Although the exact mechanism of VEGF induction in PD is unclear, VEGF concentrations in drained dialysate correlate with IL-6 levels, suggesting a link between these cytokines. Human peritoneal mesothelial cells (HPMCs), the main source of IL-6 and VEGF in the peritoneum, do not bear the cognate IL-6 receptor and are thus unable to respond to classic IL-6 receptor signaling. Here, we investigated whether VEGF release by HPMCs is controlled by IL-6 in combination with its soluble receptor (IL-6 trans-signaling). Although treatment with either IL-6 or soluble IL-6 receptor (sIL-6R) alone had no effect on VEGF production, stimulation of HPMCs with IL-6 in combination with sIL-6R promoted VEGF expression and secretion through a transcriptional mechanism involving STAT3 and SP4. Conditioned medium from HPMCs cultured with IL-6 and sIL-6R promoted angiogenic endothelial tube formation, which could be blocked by silencing SP4. , induction of peritoneal inflammation in wild-type and IL-6-deficient mice showed IL-6 involvement in the control of and expression and new vessel formation, confirming the role of IL-6 trans-signaling in these processes. Taken together, these findings identify a novel mechanism linking IL-6 trans-signaling and angiogenesis in the peritoneal membrane.

The cytokine IL-6 controls the survival, proliferation and effector characteristics of lymphocytes through activation of the transcription factors STAT1 and STAT3. While STAT3 activity is an ever-present feature of IL-6 signaling in CD4 + T cells, prior T-cell receptor activation limits the IL-6 control of STAT1 in effector and memory populations. Here we show that STAT1 phosphorylation in response to IL-6 was regulated by protein tyrosine phosphatases (PTPN2, PTPN22) expressed in response to the activation of naïve CD4 + T cells. Transcriptomic and chromatin immunoprecipitation-sequencing of IL-6 responses in naïve and effector memory CD4 + T cells showed how the suppression of STAT1 activation shaped the functional identity and effector characteristics of memory CD4 + T cells. Thus, protein tyrosine phosphatases induced by activation of naïve T cells determined the way activated or memory CD4 + T cells sensed and interpreted cytokine signals.

The cytokine IL-6 performs critical functions in various tissue types but is implicated in autoimmune disease. Therefore, precisely targeting the pathway by which IL-6 induces inflammatory immune cell activation could leave other signaling pathways and functions of IL-6 intact. Currently, such targeted molecules lack sufficient selectivity. Heise et al. developed a chimeric molecule that bound to and "trapped" a critical IL-6 trans-signaling protein complex and that was smaller, had greater selectivity for the IL-6 complex over a similar IL-11 complex, and more effectively inhibited the IL-6-induced inflammatory activation of cultured T cells. These findings may lead to improved therapeutics for patients with autoimmune disease.

Objective Ectopic lymphoid structures (ELS) develop at sites of infection, autoimmunity, and cancer. In patients with Sjögren's syndrome (SS), ELS support autoreactive B cell activation and lymphomagenesis. Interleukin‐27 (IL‐27) is a key regulator of adaptive immunity and limits Th17 cell–driven pathology. We undertook this study to elucidate the role of IL‐27 in ELS formation and function in autoimmunity using a murine model of sialadenitis and in patients with SS. Methods ELS formation was induced in wild‐type and Il27ra−/− mice via salivary gland (SG) cannulation of a replication‐deficient adenovirus in the presence or absence of IL‐17A neutralization. In SG biopsy samples, IL‐27–producing cells were identified by multicolor immunofluorescence microscopy. Lesional and circulating IL‐27 levels were determined by gene expression and enzyme‐linked immunosorbent assay. The in vitro effect of IL‐27 on T cells was assessed using fluorescence‐activated cell sorting and cytokine release. Results In experimental sialadenitis, Il27ra−/− mice had larger and more hyperactive ELS (focus score; P < 0.001), increased autoimmunity, and an expanded Th17 response (P < 0.001), compared to wild‐type mice. IL‐17 blockade in Il27ra−/− mice suppressed the aberrant ELS response (B and T cell reduction against control; P < 0.01). SS patients displayed increased circulating IL‐27 levels (P < 0.01), and in SG biopsy samples, IL‐27 was expressed by DC‐LAMP+ dendritic cells in association with CD3+ T cells. Remarkably, in SS T cells (but not in T cells from patients with rheumatoid arthritis or healthy controls), IL‐27–mediated suppression of IL‐17 secretion was severely impaired and associated with an aberrant interferon‐γ release upon IL‐27 stimulation. Conclusion Our data indicate that the physiologic ability of IL‐27 to limit the magnitude and function of ELS through control of Th17 cell expansion is severely impaired in SS patients, highlighting a defective immunoregulatory checkpoint in this condition.

BackgroundApproximately 30% of Sjögren’s Syndrome (SS) patients develop Ectopic Lymphoid Structures (ELS) in their salivary glands (SG). ELS play an active role in autoimmunity and contribute to the development of MALT lymphoma. Interleukin 27 (IL-27) exerts key immunomodulatory actions on CD4 T cells with both pro and anti-inflammatory roles but its role in the formation and regulation of ELS in the salivary glands of SS is unknown.ObjectivesWe first used a murine model of inducible SG ELS to elucidate the role of IL-27 and its interaction with IL-17 in the regulation of ELS formation and function. We then extended our observations on a cohort of SS patients to identify IL-27 cellular source, target cells and functional properties in modulating peripheral and lesional CD4 T cells function.MethodsTo trigger ELS formation a single dose of reporter-encoding adenovirus was delivered directly to the SG of wild-type (WT) and IL-27RA-deficient (KO) mice. For IL-17 blockade anti-mouse IL-17A antibody was administered systemically. ELS development and peripheral immune responses were tracked by immuno-histopathology, FACS, and qPCR. Minor SG biopsies were collected from SS and non-specific sialadenitis (sicca) patients. Peripheral blood mononuclear cells (PBMC) isolated from patients and age/sex matched healthy donors (HD). For in vitro experiments PBMCs, isolated CD4 T cells and parotid gland MCs were incubated with IL-27 and analysed by FACS for CD4 T cell subsets while cytokines levels were measured intracellularly by FACS and in culture supernatants. Tissue IL-27 was assessed in SS SG sections by multicolour immunofluorescence to identify IL-27 producing cells.ResultsIn WT mice, SG ELS formation was preceded by an upregulation of IL-27p28 and infiltration of IL-27 producing cells (CD11b+ first followed by CD4 and CD8 T cells). KO mice displayed larger, more abundant ELS in the SG with more germinal centres and higher levels of ELS-related genes (Cxcl13, Ccl19, Ltb, Aid) compared to WT mice. During ELS formation, KO mice had an uncontrolled SG Th17 response and systemic IL-17A blockade caused reduction in ELS size and in the expression of ELS-related genes. In SS patients SG and serum, we observed higher expression levels of IL-27 transcripts and protein, respectively, compared to sicca, while SG IL-27 was selectively increased in the ELS+ subset of SS. Immunofluorescence staining for IL-27 revealed its presence primarily in the T cell rich areas of SG ELS with frequent co-localization with DC-LAMP+ dendritic cells. Finally, while IL-27 was able to significantly downregulate IL-17 production in HD, CD4 T cells from patients with SS failed to downregulate IL-17 but showed an aberrant IFNγ release upon IL-27 incubation. We did not observe any difference in IL-27R expression or downstream STAT1/3 phosphorylation between SS and HD.ConclusionIL-27 is a critical regulator of the magnitude of the germinal centre response in the SG by restricting Th17 expansion. Both in murine inducible ELS and in patients with SS, dendritic c...