ObjectivesTo explore the relevance of T-follicular-helper (Tfh) and pathogenic peripheral-helper T-cells (Tph) in promoting ectopic lymphoid structures (ELS) and B-cell mucosa-associated lymphoid tissue (MALT) lymphomas (MALT-L) in Sjögren’s syndrome (SS) patients.MethodsSalivary gland (SG) biopsies with matched peripheral blood were collected from four centres across the European Union. Transcriptomic (microarray and quantitative PCR) analysis, FACS T-cell immunophenotyping with intracellular cytokine detection, multicolor immune-fluorescence microscopy and in situ hybridisation were performed to characterise lesional and circulating Tfh and Tph-cells. SG-organ cultures were used to investigate functionally the blockade of T-cell costimulatory pathways on key proinflammatory cytokine production.ResultsTranscriptomic analysis in SG identified Tfh-signature, interleukin-21 (IL-21) and the inducible T-cell co-stimulator (ICOS) costimulatory pathway as the most upregulated genes in ELS+SS patients, with parotid MALT-L displaying a 400-folds increase in IL-21 mRNA. Peripheral CD4+CXC-motif chemokine receptor 5 (CXCR5)+programmed cell death protein 1 (PD1)+ICOS+ Tfh-like cells were significantly expanded in ELS+SS patients, were the main producers of IL-21, and closely correlated with circulating IgG and reduced complement C4. In the SG, lesional CD4+CD45RO+ICOS+PD1+ cells selectively infiltrated ELS+ tissues and were aberrantly expanded in parotid MALT-L. In ELS+SG and MALT-L parotids, conventional CXCR5+CD4+PD1+ICOS+Foxp3- Tfh-cells and a uniquely expanded population of CXCR5-CD4+PD1hiICOS+Foxp3- Tph-cells displayed frequent IL-21/interferon-γ double-production but poor IL-17 expression. Finally, ICOS blockade in ex vivo SG-organ cultures significantly reduced the production of IL-21 and inflammatory cytokines IL-6, IL-8 and tumour necrosis factor-α (TNF-α).ConclusionsOverall, these findings highlight Tfh and Tph-cells, IL-21 and the ICOS costimulatory pathway as key pathogenic players in SS immunopathology and exploitable therapeutic targets in SS.

Devil Facial Tumour 2 (DFT2) is a recently discovered contagious cancer circulating in the Tasmanian devil (Sarcophilus harrisii), a species which already harbours a more widespread contagious cancer, Devil Facial Tumour 1 (DFT1). Here we show that in contrast to DFT1, DFT2 cells express major histocompatibility complex (MHC) class I molecules, demonstrating that loss of MHC is not necessary for the emergence of a contagious cancer. However, the most highly expressed MHC class I alleles in DFT2 cells are common among host devils or non-polymorphic, reducing immunogenicity in a population sharing these alleles. In parallel, MHC class I loss is emerging in vivo, thus DFT2 may be mimicking the evolutionary trajectory of DFT1. Based on these results we propose that contagious cancers may exploit partial histocompatibility between the tumour and host, but that loss of allogeneic antigens could facilitate widespread transmission of DFT2.

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.

Salivary glands (SGs) represent a permissive site for several sialotropic viruses whose persistence is linked to the development of autoimmunity. Natural Killer (NK) cells play a key role in viral clearance but their involvement in viral infection control and in tertiary lymphoid structures (TLS) development within SGs is unknown. By using an inducible model of TLS in the SGs of wild‐type C57BL/6 mice, induced by the local delivery of a replication‐defective adenovirus (AdV), we demonstrated that circulating NK cells are rapidly recruited to SGs and highly enrich the early inflammatory infiltrate prior to TLS development. NK cells migrating to SGs in response to AdV infection up‐regulate NKp46, undergo proliferation, acquire cytotoxic potential, produce Granzyme‐B and IFN‐γ, and reduce viral load in the acute phase of the infection. Nonetheless, the selective depletion of both circulating and infiltrating NK cells in AdV‐infected mice neither affect the development and frequency of TLS nor the onset of autoimmunity. These data demonstrate that, upon local viral delivery of AdV, peripheral NK cells homing to SGs can exert an early control of the viral infection but are dispensable for the formation of TLS and breach of immunologic tolerance.