VISTA Deficiency Exacerbates the Development of Pulmonary Fibrosis by Promoting Th17 Differentiation.

Background: Interstitial lung disease (ILD), characterized by pulmonary fibrosis (PF), represents the end-stage of various ILDs. The immune system plays an important role in the pathogenesis of PF. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an immune checkpoint with immune suppressive functions. However, its specific role in the development of PF and the underlying mechanisms remain to be elucidated. Methods: We assessed the expression of VISTA in CD4 T cells from patients with connective tissue disease-related interstitial lung disease (CTD-ILD). Spleen cells from wild-type (WT) or Vsir -/- mice were isolated and induced for cell differentiation in vitro. Additionally, primary lung fibroblasts were isolated and treated with interleukin-17A (IL-17A). Mice were challenged with bleomycin (BLM) following VISTA blockade or Vsir knockout. Moreover, WT or Vsir -/- CD4 T cells were transferred into Rag1 -/- mice, which were then challenged with BLM. Results: VISTA expression was decreased in CD4 T cells from patients with CTD-ILD. Vsir deficiency augmented T-helper 17 (Th17) cell differentiation in vitro. Furthermore, IL-17A enhanced the production of inflammatory cytokines, as well as the differentiation and migration of lung fibroblasts. Both VISTA blockade and knockout of Vsir increased the percentage of IL-17A-producing Th17 cells and promoted BLM-induced PF. In addition, mice receiving Vsir -/- CD4 T cells exhibited a higher percentage of Th17 cells and more severe PF compared to those receiving WT CD4 T cells. Conclusion: These findings demonstrate the significant role of VISTA in modulating the development of PF by controlling Th17 cell differentiation. These insights suggest that targeting VISTA could be a promising therapeutic strategy for PF.

C5a-C5aR1 axis controls mitochondrial fission to promote podocyte injury in lupus nephritis.

Podocytes are essential to maintaining the integrity of the glomerular filtration barrier, but they are frequently affected in lupus nephritis (LN). Here, we show that the significant upregulation of Drp1S616 phosphorylation in podocytes promotes mitochondrial fission, leading to mitochondrial dysfunction and podocyte injury in LN. Inhibition or knockdown of Drp1 promotes mitochondrial fusion and protects podocytes from injury induced by LN serum. In vivo, pharmacological inhibition of Drp1 reduces the phosphorylation of Drp1S616 in podocytes in lupus-prone mice. Podocyte injury is reversed when Drp1 is inhibited, resulting in the alleviation of proteinuria. Mechanistically, complement component C5a (C5a) upregulates the phosphorylation of Drp1S616 and promotes mitochondrial fission in podocytes. Moreover, the expression of C5a receptor 1 (C5aR1) is notably upregulated in podocytes in LN. C5a-C5aR1 axis-controlled phosphorylation of Drp1S616 and mitochondrial fission are substantially suppressed when C5aR1 is knocked down by siRNA. Moreover, lupus-prone mice treated with C5aR inhibitor show reduced phosphorylation of Drp1S616 in podocytes, resulting in significantly less podocyte damage. Together, this study uncovers a novel mechanism by which the C5a-C5aR1 axis promotes podocyte injury by enhancing Drp1-mediated mitochondrial fission, which could have significant implications for the treatment of LN.

TIGIT regulates CD4+ T cell immunity against polymicrobial sepsis.

Background: Sepsis is one of the major causes of death and increased health care burden in modern intensive care units. Immune checkpoints have been prompted to be key modulators of T cell activation, T cell tolerance and T cell exhaustion. This study was designed to investigate the role of the negative immune checkpoint, T cell immunoglobulin and ITIM domain (TIGIT), in the early stage of sepsis. Method: An experimental murine model of sepsis was developed by cecal ligation and puncture (CLP). TIGIT and CD155 expression in splenocytes at different time points were assessed using flow cytometry. And the phenotypes of TIGIT-deficient (TIGIT-/-) and wild-type (WT) mice were evaluated to explore the engagement of TIGIT in the acute phase of sepsis. In addition, the characteristics were also evaluated in the WT septic mice pretreated with anti-TIGIT antibody. TIGIT and CD155 expression in tissues was measured using real-time quantitative PCR and immunofluorescence staining. Proliferation and effector function of splenic immune cells were evaluated by flow cytometry. Clinical severity and tissue injury were scored to evaluate the function of TIGIT on sepsis. Additionally, tissue injury biomarkers in peripheral blood, as well as bacterial load in peritoneal lavage fluid and liver were also measured. Results: The expression of TIGIT in splenic T cells and NK cells was significantly elevated at 24 hours post CLP.TIGIT and CD155 mRNA levels were upregulated in sepsis-involved organs when mice were challenged with CLP. In CLP-induced sepsis, CD4+ T cells from TIGIT-/- mice shown increased proliferation potency and cytokine production when compared with that from WT mice. Meanwhile, innate immune system was mobilized in TIGIT-/- mice as indicated by increased proportion of neutrophils and macrophages with potent effector function. In addition, tissue injury and bacteria burden in the peritoneal cavity and liver was reduced in TIGIT-/- mice with CLP induced sepsis. Similar results were observed in mice treated with anti-TIGIT antibody. Conclusion: TIGIT modulates CD4+ T cell response against polymicrobial sepsis, suggesting that TIGIT could serve as a potential therapeutic target for sepsis.

Metabolic dysregulation of lymphocytes in autoimmune diseases.

Lymphocytes are crucial for protective immunity against infection and cancers; however, immune dysregulation can lead to autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Metabolic adaptation controls lymphocyte fate; thus, metabolic reprogramming can contribute to the pathogenesis of autoimmune diseases. Here, we summarize recent advances on how metabolic reprogramming determines the autoreactive and proinflammatory nature of lymphocytes in SLE and RA, unraveling molecular mechanisms and providing therapeutic targets for human autoimmune diseases.

Efficacy and safety of tripterygium wilfordii Hook F plus TNF inhibitor for active rheumatoid arthritis: A multicentre, randomized, double-blind, triple-dummy controlled trial.

An investigator-initiated, multicentre, randomized, double-blind, triple-dummy, controlled trial was conducted at 14 tertiary rheumatology centers in China to evaluate the efficacy and safety of Tripterygium wilfordii Hook F (TwHF) with recombinant human TNF receptor IgGFc fusion protein (rhTNFR-Fc) in active Rheumatoid Arthritis (RA). Primary endpoint was the proportion of patients achieved a 50% improvement of American College of Rheumatology criteria (ACR50) in TwHF+rhTNFR-Fc vs. methotrexate (MTX) group at week 12. ACR50 was achieved in 57.1% (72/126), 41.3% (52/126), 23.0% (29/126), and 26.2% (33/126) patients receiving TwHF+rhTNFR-Fc, MTX + rhTNFR-Fc, TwHF and MTX monotherapy, respectively, at week 12 (TwHF+rhTNFR-Fc vs. other three groups, all p < 0.05). No statistical difference in serious adverse events or adverse events leading to discontinuation of study across all groups was documented. TwHF+rhTNFR-Fc was superior to MTX for active RA, and was more effective than MTX + rhTNFR-Fc on ACR50, with a similar safety profile. Trial registration:ClinicalTrials.govNCT03589833.

Spleen fibroblastic reticular cell-derived acetylcholine promotes lipid metabolism to drive autoreactive B cell responses.

Autoreactive B cell responses are essential for the development of systemic lupus erythematosus (SLE). Fibroblastic reticular cells (FRCs) are known to construct lymphoid compartments and regulate immune functions. Here, we identify spleen FRC-derived acetylcholine (ACh) as a key factor that controls autoreactive B cell responses in SLE. In SLE, CD36-mediated lipid uptake leads to enhanced mitochondrial oxidative phosphorylation in B cells. Accordingly, the inhibition of fatty acid oxidation results in reduced autoreactive B cell responses and ameliorated diseases in lupus mice. Ablation of CD36 in B cells impairs lipid uptake and differentiation of autoreactive B cells during autoimmune induction. Mechanistically, spleen FRC-derived ACh promotes lipid influx and generation of autoreactive B cells through CD36. Together, our data uncover a novel function of spleen FRCs in lipid metabolism and B cell differentiation, placing spleen FRC-derived ACh in a key position in promoting autoreactive B cells in SLE.

Impacts of delta and omicron variants on inactivated SARS-CoV-2 vaccine-induced T cell responses in patients with autoimmune diseases and healthy controls.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes coronavirus disease 2019 (COVID-19), which is still devastating economies and communities globally. The increasing infections of variants of concern (VOCs) in vaccinated population have raised concerns about the effectiveness of current vaccines. Patients with autoimmune diseases (PAD) under immunosuppressant treatments are facing higher risk of infection and potentially lower immune responses to SARS-CoV-2 vaccination. METHODS: Blood samples were collected from PAD or healthy controls (HC) who finished two or three doses of inactivated vaccines. Spike peptides derived from wild-type strain, delta, omicron BA.1 were utilised to evaluate T cell responses and their cross-recognition of delta and omicron in HC and PAD by flow cytometry and ex vivo IFNγ-ELISpot. RESULTS: We found that inactivated vaccine-induced spike-specific memory T cells were long-lasting in both PAD and HC. These spike-specific T cells were highly conserved and cross-recognized delta and omicron. Moreover, a third inactivated vaccine expanded spike-specific T cells that responded to delta and omicron spike peptides substantially in both PAD and HC. Importantly, the polyfunctionality of spike-specific memory T cells was preserved in terms of cytokine and cytotoxic responses. Although the extent of T cell responses was lower in PAD after two-dose, T cell responses were boosted to a greater magnitude in PAD by the third dose, bringing comparable spike-specific T cell immunity after the third dose. CONCLUSION: Inactivated vaccine-induced spike-specific T cells remain largely intact against delta and omicron variants. This study expands our understanding of inactivated vaccine-induced T cell responses in PAD and HC, which could have important indications for vaccination strategy.

NAMPT is a metabolic checkpoint of IFNγ-producing CD4+ T cells in lupus nephritis.

Interferon γ (IFNγ) produced by T cells represents the featured cytokine and is central to the pathogenesis of lupus nephritis (LN). Here, we identified nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the salvage NAD+ biosynthetic pathway, as playing a key role in controlling IFNγ production by CD4+ T cells in LN. Our data revealed that CD4+ T cells from LN showed an enhanced NAMPT-mediated NAD+ biosynthetic process, which was positively correlated with IFNγ production in CD4+ T cells. NAMPT promoted aerobic glycolysis and mitochondrial respiration in CD4+ T cells from patients with LN or MRL/lpr mice through the production of NAD+. By orchestrating metabolic fitness, NAMPT promoted translational efficiency of Ifng in CD4+ T cells. In vivo, knockdown of NAMPT by small interfering RNA (siRNA) or pharmacological inhibition of NAMPT by FK866 suppressed IFNγ production in CD4+ T cells, leading to reduced inflammatory infiltrates and ameliorated kidney damage in lupus mice. Taken together, this study uncovers a metabolic checkpoint of IFNγ-producing CD4+ T cells in LN in which therapeutically targeting NAMPT has the potential to normalize metabolic competence and blunt pathogenicity of CD4+ T cells in LN.

A clinical practice guideline for the screening and assessment of enthesitis in patients with spondyloarthritis.

Objective: The aim of this review is to provide guidance on the selection of approaches to the screening and assessment of enthesitis in patients with spondyloarthritis (SpA). Methods: Twenty-four questions regarding the approaches to the screening and assessment of enthesitis and the implementation details were devised, followed by a systemic literature review. The Grading of Recommendations Assessment, Development, and Evaluation methodology was employed in the development of this guideline, with modifications to evaluate non-interventional approaches under comprehensive consideration of costs, accessibility, and evidence strength. A consensus from the voting panel was required for the inclusion of the final recommendations and the strength of each recommendation. Results: Seventeen recommendations (including five strong recommendations) were included in this guideline. The voting panel expressed unequivocal support for the necessity of screening and assessment of enthesitis in patients with SpA. It was agreed unanimously that symptom evaluation and physical examination should serve as the initial steps to the recognition of enthesitis, whereas Maastricht Ankylosing Spondylitis Enthesitis Score is a reliable tool in both clinical trials and daily medical practice. Ultrasound examination is another reliable tool, with power Doppler ultrasound as an informative addition. Notwithstanding its high resolution, MRI is limited by the costs and relatively low accessibility, whereas radiographs had low sensitivity and therefore should be rendered obsolete in the assessment of enthesitis. PET/CT was strongly opposed in the detection of enthesitis. Conclusion: This guideline provides clinicians with information regarding the screening and assessment of enthesitis in patients with SpA. However, this guideline does not intend on dictating choices, and the ultimate decisions should be made in light of the actual circumstances of the facilities.

Activation of necroptosis pathway in podocyte contributes to the pathogenesis of focal segmental glomerular sclerosis.

BACKGROUND: Focal segmental glomerulosclerosis (FSGS) is characterized by podocyte damage and severe proteinuria. The exact mechanism of podocyte damage and loss remains unclear. Necroptosis, a lytic form of programmed cell death mediated by RIP3 and MLKL, has emerged as an important cell death pattern in multiple tissues and cell types. Necroptosis in FSGS has not been investigated. METHODS: Public GEO data regarding podocyte treated with vehicle or adriamycin (ADR) was identified and analyzed. Cultured human podocytes were used to explore the activation of necroptosis upon ADR stimulation. The expression of necroptosis pathway molecules, p-RIP3 and p-MLKL, was examined in the glomeruli and defoliated urinary podocytes of patients with FSGS. The effect of necroptosis inhibition was assessed in ADR-induced glomerulopathy mice using GSK872. RESULTS: Publicly available RNA-sequencing data analysis showed that both necroptosis and NLRP3 inflammasome pathway were up-regulated in ADR-injured podocyte. Immunofluorescent staining showed increased expression of p-RIP3 and p-MLKL, the active forms of RIP3 and MLKL, in podocytes of FSGS patients and ADR-induced glomerulopathy mice but not in the normal control. GSK872, an RIP3 kinase inhibitor, significantly inhibited the expression of p-RIP3, p-MLKL and activation of NLRP3 in cultured podocytes treated with ADR. GSK872 treatment of mice with ADR-induced nephropathy resulted in the reduced expression of p-RIP3, p-MLKL, NLRP3 and caspase-1 p20. GSK872 also significantly inhibited the expression of p-MLKL in the podocytes of ADR-induced nephropathy, resulting in the attenuation of proteinuria and renal histological lesions. CONCLUSION: Necroptosis pathway might be a valuable target for the treatment of FSGS.

Iron controls T helper cell pathogenicity by promoting glucose metabolism in autoimmune myopathy.

BACKGROUND: T helper cells in patients with autoimmune disease of idiopathic inflammatory myopathies (IIM) are characterized with the proinflammatory phenotypes. The underlying mechanisms remain unknown. METHODS: RNA sequencing was performed for differential expression genes. Gene expression in CD4+ T-cells was confirmed by quantitative real-time PCR. CD4+ T-cells from IIM patients or healthy controls were evaluated for metabolic activities by Seahorse assay. Glucose uptake, T-cell proliferation and differentiation were evaluated and measured by flow cytometry. Human CD4+ T-cells treated with iron chelators or Pfkfb4 siRNA were measured for glucose metabolism, proliferation and differentiation. Signalling pathway activation was evaluated by western blot and flow cytometry. Mouse model of experimental autoimmune myositis (EAM) were induced and treated with iron chelator or rapamycin. CD4+ T-cell differentiation and muscle inflammation in the EAM mice were evaluated. RESULTS: RNA-sequencing analysis revealed that iron was involved with glucose metabolism and CD4+ T-cell differentiation. IIM patient-derived CD4+ T-cells showed enhanced glycolysis and mitochondrial respiration, which was inhibited by iron chelation. CD4+ T-cells from patients with IIM was proinflammatory and iron chelation suppressed the differentiation of interferon gamma (IFNγ)- and interleukin (IL)-17A-producing CD4+ T-cells, which resulted in an increased percentage of regulatory T (Treg) cells. Mechanistically, iron promoted glucose metabolism by an upregulation of PFKFB4 through AKT-mTOR signalling pathway. Notably, the knockdown of Pfkfb4 decreased glucose influx and thus suppressed the differentiation of IFNγ- and IL-17A-producing CD4+ T-cells. In vivo, iron chelation inhibited mTOR signalling pathway and reduced PFKFB4 expression in CD4+ T-cells, resulting in reduced proinflammatory IFNγ- and IL-17A-producing CD4+ T-cells and increased Foxp3+ Treg cells, leading to ameliorated muscle inflammation. CONCLUSIONS: Iron directs CD4+ T-cells into a proinflammatory phenotype by enhancing glucose metabolism. Therapeutic targeting of iron metabolism should have the potential to normalize glucose metabolism in CD4+ T-cells and reverse their proinflammatory phenotype in IIM.

TIGIT Deficiency Protects Mice From DSS-Induced Colitis by Regulating IL-17A-Producing CD4+ Tissue-Resident Memory T Cells.

Tissue-resident memory T cells (TRM cells) have been shown to play an instrumental role in providing local immune responses for pathogen clearance in barrier tissues. However, their contribution to inflammatory bowel diseases (IBDs) and the underlying regulation are less clear. Here, we identified a critical role of T-cell immunoreceptor with immunoglobulin and ITIM (TIGIT) in regulating CD4+ TRM cells in an experimental model of intestinal inflammation. We found that CD4+ TRM cells were increased and correlated with disease activities in mice with dextran sulfate sodium (DSS)-induced colitis. Phenotypically, these CD4+ TRM cells could be classified into CD69+CD103- and CD69+CD103+ subsets. Functionally, these CD4+ TRM cells were heterogeneous. CD69+CD103- CD4+ TRM cells were pro-inflammatory and produced interferon-γ (IFNγ) and interleukin-17A (IL-17A), which accounted for 68.7% and 62.9% of total IFNγ+ and IL-17A+ CD4+ T cells, respectively, whereas CD69+CD103+ CD4+ TRM cells accounted for 73.7% Foxp3+ regulatory T cells. TIGIT expression was increased in CD4+ T cells in the gut of mice with DSS-induced colitis. TIGIT deficiency impaired IL-17A expression in CD69+CD103- CD4+ TRM cells specifically, resulting in ameliorated gut inflammation and tissue injury. Together, this study provides new insights into the regulation of gut inflammation that TIGIT deficiency protects mice from DSS-induced colitis, which might have a potential therapeutic value in the treatment of IBDs.

CaMK4 Promotes Acute Lung Injury Through NLRP3 Inflammasome Activation in Type II Alveolar Epithelial Cell.

Background: Type II alveolar epithelial cell (AEC II), in addition to its roles in maintaining lung homeostasis, takes an active role in inflammatory response during acute lung injury (ALI). Ca2+/calmodulin-dependent protein kinase IV (CaMK4) activated by Ca2+/calmodulin signaling, has been implicated in immune responses. This study was to investigate the roles of CaMK4 in the development of ALI and the underlying mechanisms. Methods: CaMK4 inhibitor KN-93 was used to investigate the effects of CaMK4 on NLRP3 inflammasome activation. The effects of KN-93 on disease development of lipopolysaccharide (LPS)-induced ALI were also evaluated. The role of CaMK4 on NLRP3 inflammasome activation was explored in human AEC II cell line A549 using KN-93 or CaMK4 siRNA. NLRP3 inflammasome activation was measured by histology immunofluorescence and Western blot. IL-1ß and IL-18 were measured by ELISA. Results: Phosphorylation of CaMK4 and the expression of NLRP3 and Caspase-1 p20 were increased in the lungs of LPS-induced ALI mice, which was suppressed by KN-93 as measured by Western blot. Further, the activation of NLRP3 inflammasome was detected in AEC II from patients with acute respiratory distress syndrome (ARDS) and LPS-induced ALI mice. In vitro, inhibition or silencing CaMK4 in AEC II significantly inhibited NLRP3 inflammasome activation, resulting in reduced IL-1ß production. The inhibition of NLRP3 inflammasome and decreased IL-1ß/IL-18 production by KN-93 led to reduced inflammatory infiltration and ameliorated lung injury in LPS-induced ALI mice. Conclusion: CaMK4 controls the activation of NLRP3 inflammasome in AEC II during LPS-induced ALI. CaMK4 inhibition could be a novel therapeutic approach for the treatment of ALI.

Tfh cells with NLRP3 inflammasome activation are essential for high-affinity antibody generation, germinal centre formation and autoimmunity.

OBJECTIVE: NLRP3 inflammasome regulates T cell responses. This study examined the roles of NLRP3 inflammasome activation in the regulation of T follicular helper (Tfh) cells during humoral response to T dependent antigens and in systemic lupus erythematosus (SLE). METHODS: NLRP3 inflammasome activation of Tfh cells was studied in B6, MRL/lpr and NZM2328 mice and in SLE patients and healthy controls using a fluorescence-labelled caspase-1 inhibitor probe. MCC950, a selective inhibitor of NLRP3, was used to investigate the relation between NLRP3 inflammasome activation and germinal centre (GC) reaction, Ab responses to immunisation, and autoantibody production. RESULTS: NLRP3 inflammasome activation in Tfh cells after immunisation was identified in B6 mice. MCC950 inhibited humoral responses to sheep red blood cell and NP-CGG with reduction of the GC reaction. B6 mice with lymphoid cell-specific deletion of NLRP3 or Casp1 mounted suboptimal humoral responses with impaired GC formation and defective affinity maturation. In MRL/lpr and NZM2328 mice, inhibition of NLRP3 activation suppressed NLRP3 activated Tfh cell expansion as well as attenuated lupus-like phenotypes. Tfh cells with activated NLRP3 inflammasome exhibited increased expression of molecules for Tfh cell function and differentiation, and had greater ability to activate B cells. In SLE patients, disease activity was positively correlated with an increase in the activated NLRP3+ Tfh population and this population was markedly reduced in response to therapy. CONCLUSIONS: The activation of NLRP3 inflammasome in Tfh cells is an integral part of responses to immunisation. The activated NLRP3+ Tfh population is essential for optimal humoral responses, GC formation and autoimmunity.

Fine Comparison of the Efficacy and Safety Between GB242 and Infliximab in Patients with Rheumatoid Arthritis: A Phase III Study.

INTRODUCTION: This phase III trial (NCT04178850) evaluated the efficacy, safety, and immunogenicity of GB242, an infliximab biosimilar, vs. infliximab (Remicade®) reference product in patients with moderate-to-severe active rheumatoid arthritis (RA) combination with methotrexate (MTX) therapy. METHODS: Patients were randomized in a 1:1 ratio to receive either GB242 or INF (3 mg/kg). Therapeutic equivalence of clinical response according to the American College of Rheumatology 20% (ACR20) response rate at week 30 was declared if the two-sided 95% CI for the treatment difference was within ± 14%. The comparison of GB242 with INF also included the proportion of patients achieving a week 30 ACR 50 response, ACR70 response, change in Disease Activity Score 28 (DAS28), as well as safety and immunogenicity. RESULTS: A total of 570 subjects were randomized into GB242 (N = 285) or INF (N = 285) and 283 subjects in each group were analyzed. At week 30, the ACR20 was 62.54% for the GB242 group (95% CI 56.62-68.20%) and 56.89% for the INF group (95% CI 50.90-62.74%). The difference between the two groups was 5.65% with a 95% CI of - 2.48 to 13.74. ACR50 response was 37.12% for GB242 and 32.86% for INF at week 30. ACR70 response was 19.79% for GB242 and 16.96% for INF at week 30, respectively. The incidence of treatment-emergent adverse events was comparable (77.4% in GB242 vs. 80.2% in INF) and detection of antidrug antibodies (ADA) to infliximab up to week 30 (60.8% in GB242 vs. 59.4% in INF) was comparable. CONCLUSIONS: GB242 demonstrated equivalent efficacy to INF at week 30. Moreover, GB242 was well tolerated, with a similar immunogenicity and safety profile comparable to INF.

CRAC Channel Controls the Differentiation of Pathogenic B Cells in Lupus Nephritis.

Store-operated Ca2+ release-activated Ca2+ (CRAC) channel is the main Ca2+ influx pathway in lymphocytes and is essential for immune response. Lupus nephritis (LN) is an autoimmune disease characterized by the production of autoantibodies due to widespread loss of immune tolerance. In this study, RNA-seq analysis revealed that calcium transmembrane transport and calcium channel activity were enhanced in naive B cells from patients with LN. The increased expression of ORAI1, ORAI2, and STIM2 in naive B cells from patients with LN was confirmed by flow cytometry and Western blot, implying a role of CRAC channel in B-cell dysregulation in LN. For in vitro study, CRAC channel inhibition by YM-58483 or downregulation by ORAI1-specific small-interfering RNA (siRNA) decreased the phosphorylation of Ca2+/calmodulin-dependent protein kinase2 (CaMK2) and suppressed Blimp-1 expression in primary human B cells, resulting in decreased B-cell differentiation and immunoglobulin G (IgG) production. B cells treated with CaMK2-specific siRNA showed defects in plasma cell differentiation and IgG production. For in vivo study, YM-58483 not only ameliorated the progression of LN but also prevented the development of LN. MRL/lpr lupus mice treated with YM-58483 showed lower percentage of plasma cells in the spleen and reduced concentration of anti-double-stranded DNA antibodies in the sera significantly. Importantly, mice treated with YM-58483 showed decreased immune deposition in the glomeruli and alleviated kidney damage, which was further confirmed in NZM2328 lupus mice. Collectively, CRAC channel controlled the differentiation of pathogenic B cells and promoted the progression of LN. This study provides insights into the pathogenic mechanisms of LN and that CRAC channel could serve as a potential therapeutic target for LN.

Circulating TFH cells is correlated with disease activity in anti-MDA5 antibody positive idiopathic inflammatory myopathies.

OBJECTIVES: Idiopathic inflammatory myopathies (IIM) are a group of disorders characterised by the production of autoantibodies and inflammatory infiltrates in the skeletal muscles. Follicular T helper (TFH) cells are known to be crucial for B cell differentiation and autoantibody production in autoimmune diseases. The aim of this study was to investigate the involvement of TFH cells in IIM. METHODS: Circulating TFH cells in 44 IIM patients or 11 age- and gender-matched healthy controls (HCs) were measured by flow cytometry. ICOS, PD-1, active caspase-1 and Ki-67 expression in TFH cells was examined. The correlations between the frequency of TFH cells and clinical disease activities were also analysed. RESULTS: The frequency of TFH cells was 16.6% in IIM patients with anti-melanoma differentiation-associated gene (MDA5) antibody compared to 10.6% and 12.9% in anti-MDA5 negative patients or HCs, respectively (both p<0.05). The frequency of TFH cells was positively correlated with clinical disease activities: patient/parent's assessment VAS (r=0.51, p<0.05), physician's assessment VAS (r=0.59, p<0.05) and MYOACT scores (total systems: r=0.62, p<0.05; extramuscular system: r=0.56, p<0.05; pulmonary system, r=0.55, p<0.05). The percentage of PD-1highICOShigh TFH cells was 3.68% in anti-MDA5 positive patients compared to 2.70% and 1.96% in anti-MDA5 negative patients or HCs, respectively (both p<0.05). The percentage of Ki-67 positive TFH cells was 3.50% in anti-MDA5 positive patients compared to 2.36% and 1.76% in anti-MDA5 negative patients or HCs, respectively (p<0.05). Interestingly, active caspase-1 was significantly increased in TFH cells in anti-MDA5 positive patients compared to the patients without anti-MDA5 or HCs (3.30% vs. 1.67% and 3.30% vs. 1.02%, both p<0.001). CONCLUSIONS: These data suggest a role for TFH cells in the pathogenesis of anti-MDA5 positive IIM and TFH cells might serve as a disease biomarker for this subset of patients.

JAK/STAT signaling controls the fate of CD8+CD103+ tissue-resident memory T cell in lupus nephritis.

Autoimmune mediated inflammation and renal damage in lupus nephritis (LN) depends partly on the infiltration of lymphocytes in glomeruli and renal interstitium. Here we identified a population of CD8+ T cells with a CD103+-phenotype in the healthy kidneys of human and mouse. These cells were typically CD69+CD103+ tissue-resident memory T cells (TRM) in the kidney. CD8+ TRM cells were expanded in the kidneys of patients with LN or MRL/lpr mice. The expansion of renal CD8+ TRM cells correlated significantly with kidney disease activity. These cells were active in producing cytokines, perforin and granzyme B in the kidney of MRL/lpr mice. Importantly, renal CD8+ TRM cells underwent proliferation and self-renewal to maintain a stable TRM pool in the kidney of MRL/lpr mice, contributing to renal inflammation and damage. JAK/STAT signaling in the MRL/lpr mice was required for renal TRM self-renewal as well as maintenance of effector functions. Targeting JAK/STAT signaling by tofacitinib effectively suppressed effector functions and impaired the survival of renal TRM cells in the kidney, contributing to improved kidney function in MRL/lpr mice. These results provided evidences that renal CD8+ TRM cells play a role in the pathogenesis of LN. They could serve as a therapeutic target for LN.