mRNA-delivery of IDO1 suppresses T cell-mediated autoimmunity.

Indoleamine-2,3-dioxygenase (IDO)1 degrades tryptophan, obtained through dietary intake, into immunoregulatory metabolites of the kynurenine pathway. Deficiency or blockade of IDO1 results in the enhancement of autoimmune severity in rodent models and increased susceptibility to developing autoimmunity in humans. Despite this, therapeutic modalities that leverage IDO1 for the treatment of autoimmunity remain limited.

Identification of a regulatory pathway governing TRAF1 via an arthritis-associated non-coding variant.

was among the first loci shown to confer risk for inflammatory arthritis in the absence of an associated coding variant, but its genetic mechanism remains undefined. Using Immunochip data from 3,939 patients with juvenile idiopathic arthritis (JIA) and 14,412 control individuals, we identified 132 plausible common non-coding variants, reduced serially by single-nucleotide polymorphism sequencing (SNP-seq), electrophoretic mobility shift, and luciferase studies to the single variant rs7034653 in the third intron of . Genetically manipulated experimental cells and primary monocytes from genotyped donors establish that the risk G allele reduces binding of Fos-related antigen 2 (FRA2), encoded by , resulting in reduced TRAF1 expression and enhanced tumor necrosis factor (TNF) production.

mTORC1 links pathology in experimental models of Still's disease and macrophage activation syndrome.

Still's disease is a severe inflammatory syndrome characterized by fever, skin rash and arthritis affecting children and adults. Patients with Still's disease may also develop macrophage activation syndrome, a potentially fatal complication of immune dysregulation resulting in cytokine storm. Here we show that mTORC1 (mechanistic target of rapamycin complex 1) underpins the pathology of Still's disease and macrophage activation syndrome.

Ageing and interferon gamma response drive the phenotype of neutrophils in the inflamed joint.

Objective: Neutrophils are typically the most abundant leucocyte in arthritic synovial fluid. We sought to understand changes that occur in neutrophils as they migrate from blood to joint.

Methods: We performed RNA sequencing of neutrophils from healthy human blood, arthritic blood and arthritic synovial fluid, comparing transcriptional signatures with those from murine K/BxN serum transfer arthritis.

Arthritis flares mediated by tissue-resident memory T cells in the joint.

Rheumatoid arthritis is a systemic autoimmune disease, but disease flares typically affect only a subset of joints, distributed in a distinctive pattern for each patient. Pursuing this intriguing pattern, we show that arthritis recurrence is mediated by long-lived synovial resident memory T cells (T). In three murine models, CD8+ cells bearing T markers remain in previously inflamed joints during remission.

IL-1β-driven osteoclastogenic Tregs accelerate bone erosion in arthritis.

IL-1β is a proinflammatory mediator with roles in innate and adaptive immunity. Here we show that IL-1β contributes to autoimmune arthritis by inducing osteoclastogenic capacity in Tregs. Using mice with joint inflammation arising through deficiency of the IL-1 receptor antagonist (Il1rn-/-), we observed that IL-1β blockade attenuated disease more effectively in early arthritis than in established arthritis, especially with respect to bone erosion.

Adenosine deaminase 2 as a biomarker of macrophage activation syndrome in systemic juvenile idiopathic arthritis.

Objective: Macrophage activation syndrome (MAS) is a life-threatening complication of systemic juvenile idiopathic arthritis (sJIA) characterised by a vicious cycle of immune amplification that can culminate in overwhelming inflammation and multiorgan failure. The clinical features of MAS overlap with those of active sJIA, complicating early diagnosis and treatment. We evaluated adenosine deaminase 2 (ADA2), a protein of unknown function released principally by monocytes and macrophages, as a novel biomarker of MAS.

Megakaryocyte emperipolesis mediates membrane transfer from intracytoplasmic neutrophils to platelets.

Bone marrow megakaryocytes engulf neutrophils in a phenomenon termed emperipolesis. We show here that emperipolesis is a dynamic process mediated actively by both lineages, in part through the β2-integrin/ICAM-1/ezrin pathway. Tethered neutrophils enter in membrane-bound vesicles before penetrating into the megakaryocyte cytoplasm.