Juvenile dermatomyositis disease activity is associated with the expansion of blood B and T-cell memory subsets lacking follicular markers

OBJECTIVES

To identify markers of Juvenile Dermatomyositis (JDM) disease activity (DA), which are needed to improve disease management.

METHODS

123 JDM patients and 53 healthy controls (HC) were included in the study. Laboratory tests (aldolase, CK, LDH, AST) and clinical measures of DA, including the Manual Muscle Testing (MMT-8), Childhood Myositis Assessment Scale (CMAS), and Disease Activity Scores (DAS), were recorded when available. Surface phenotype of peripheral blood mononuclear cells (PBMCs) was assessed using flow cytometry. Whole blood transcriptional profiles were studied using either RNA-sequencing or microarrays. Differential gene expression was analyzed using DESeq2, pathway, and gene ontology.

RESULTS

Conventional memory (CD27⁺ IgD^- ) B-cells expressing low CXCR5 levels (CXCR5^lo/- CM B-cells) were significantly increased in frequency and absolute numbers in two independent cohorts of JDM patients compared with HC. The frequency of CD4⁺ T-helper 2 memory (Th2) cells (CD45RA^- CXCR5^- CCR6^- CXCR3^- ) was also increased, especially in patients <1 year from diagnosis. CXCR5^lo/- CM B-cell frequency correlated with serum aldolase levels and with a blood interferon (IFN)-stimulated gene (ISG) transcriptional signature, while both the frequency and absolute cell numbers of CXCR5^lo/- CM B-cells correlated with clinical and laboratory measures of muscle DA (MMT-8, CMAS, aldolase, and LDH).

CONCLUSIONS

Our findings suggest that conventional memory B-cells lacking the CXCR5 follicular marker and CXCR5^- Th2 cells represent potential biomarkers of JDM DA and may contribute to JDM pathogenesis.

Erythroid mitochondrial retention triggers myeloid-dependent type I interferon in human SLE

Emerging evidence supports that mitochondrial dysfunction contributes to systemic lupus erythematosus (SLE) pathogenesis. Here we show that programmed mitochondrial removal, a hallmark of mammalian erythropoiesis, is defective in SLE. Specifically, we demonstrate that during human erythroid cell maturation, a hypoxia-inducible factor (HIF)-mediated metabolic switch is responsible for the activation of the ubiquitin-proteasome system (UPS), which precedes and is necessary for the autophagic removal of mitochondria. A defect in this pathway leads to accumulation of red blood cells (RBCs) carrying mitochondria (Mito+ RBCs) in SLE patients and in correlation with disease activity. Antibody-mediated internalization of Mito+ RBCs induces type I interferon (IFN) production through activation of cGAS in macrophages. Accordingly, SLE patients carrying both Mito+ RBCs and opsonizing antibodies display the highest levels of blood IFN-stimulated gene (ISG) signatures, a distinctive feature of SLE.

Longitudinal profiling of human blood transcriptome in healthy and lupus pregnancy

Healthy and uncomplicated lupus pregnancies exhibit early and sustained transcriptional modulation of lupus-related pathways. This might contribute to fetal tolerance while predisposing pregnant women to certain infections. Failure to modulate these pathways is associated with lupus pregnancy complications.

Systemic lupus erythematosus carries an increased risk of pregnancy complications, including preeclampsia and fetal adverse outcomes. To identify the underlying molecular mechanisms, we longitudinally profiled the blood transcriptome of 92 lupus patients and 43 healthy women during pregnancy and postpartum and performed multicolor flow cytometry in a subset of them. We also profiled 25 healthy women undergoing assisted reproductive technology to monitor transcriptional changes around embryo implantation. Sustained down-regulation of multiple immune signatures, including interferon and plasma cells, was observed during healthy pregnancy. These changes appeared early after embryo implantation and were mirrored in uncomplicated lupus pregnancies. Patients with preeclampsia displayed early up-regulation of neutrophil signatures that correlated with expansion of immature neutrophils. Lupus pregnancies with fetal complications carried the highest interferon and plasma cell signatures as well as activated CD4⁺ T cell counts. Thus, blood immunomonitoring reveals that both healthy and uncomplicated lupus pregnancies exhibit early and sustained transcriptional modulation of lupus-related signatures, and a lack thereof associates with adverse outcomes.

A multidimensional blood stimulation assay reveals immune alterations underlying systemic juvenile idiopathic arthritis

The etiology of autoinflammation in systemic juvenile idiopathic arthritis is unclear. Cepika et al. use integrated analysis of multidimensional blood stimulation data, applied to patients while off treatment and in complete remission, to reveal underlying cellular and molecular mechanisms that might predispose to disease.

The etiology of sporadic human chronic inflammatory diseases remains mostly unknown. To fill this gap, we developed a strategy that simultaneously integrates blood leukocyte responses to innate stimuli at the transcriptional, cellular, and secreted protein levels. When applied to systemic juvenile idiopathic arthritis (sJIA), an autoinflammatory disease of unknown etiology, this approach identified gene sets associated with specific cytokine environments and activated leukocyte subsets. During disease remission and off treatment, sJIA patients displayed dysregulated responses to TLR4, TLR8, and TLR7 stimulation. Isolated sJIA monocytes underexpressed the IL-1 inhibitor aryl hydrocarbon receptor (AHR) at baseline and accumulated higher levels of intracellular IL-1β after stimulation. Supporting the demonstration that AHR down-regulation skews monocytes toward macrophage differentiation, sJIA monocytes differentiated in vitro toward macrophages, away from the dendritic cell phenotype. This might contribute to the increased incidence of macrophage activation syndrome in these patients. Integrated analysis of high-dimensional data can thus unravel immune alterations predisposing to complex inflammatory diseases.

Transcriptional specialization of human dendritic cell subsets in response to microbial vaccines

The mechanisms by which microbial vaccines interact with human APCs remain elusive. Herein, we describe the transcriptional programs induced in human DCs by pathogens, innate receptor ligands and vaccines. Exposure of DCs to influenza, Salmonella enterica and Staphylococcus aureus allows us to build a modular framework containing 204 transcript clusters. We use this framework to characterize the responses of human monocytes, monocyte-derived DCs and blood DC subsets to 13 vaccines. Different vaccines induce distinct transcriptional programs based on pathogen type, adjuvant formulation and APC targeted. Fluzone, Pneumovax and Gardasil, respectively, activate monocyte-derived DCs, monocytes and CD1c+ blood DCs, highlighting APC specialization in response to vaccines. Finally, the blood signatures from individuals vaccinated with Fluzone or infected with influenza reveal a signature of adaptive immunity activation following vaccination and symptomatic infections, but not asymptomatic infections. These data, offered with a web interface, may guide the development of improved vaccines.