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Objectives To investigate metabolite alterations in the plasma of SLE patients to identify novel biomarkers and provide insight into SLE pathogenesis. Methods Patients with SLE (n  = 41, discovery cohort and n  = 37, replication cohort), healthy controls (n  = 30 and n  = 29) and patients with RA (n  = 19, disease control) were recruited. Metabolic profiles of the plasma samples were analysed using liquid chromatography-time-of-flight mass spectrometry and capillary electrophoresis-time-of-flight mass spectrometry. Transcriptome data was analysed using RNA-sequencing for 18 immune cell subsets. The importance of histidine (His) in plasmablast differentiation was investigated by using mouse splenic B cells. Results We demonstrate that a specific amino acid combination including His can effectively distinguish between SLE patients and healthy controls. Random forest and partial least squares-discriminant analysis identified His as an effective classifier for SLE patients. A decrease in His plasma levels correlated with damage accrual independent of prednisolone dosage and type I IFN signature. The oxidative phosphorylation signature in plasmablasts negatively correlated with His levels. We also showed that plasmablast differentiation induced by innate immune signals was dependent on His. Conclusions Plasma His levels are a potential biomarker for SLE patients and are associated with damage accrual. Our data suggest the importance of His as a pathogenic metabolite in SLE pathogenesis. [ABSTRACT FROM AUTHOR]

Objective: Idiopathic inflammatory myopathies (IIM) demonstrate characteristic clinical phenotypes depending on the myositis‐specific antibody (MSAs) present. We aimed to identify common or MSA‐specific immunological pathways in different immune cell types from peripheral blood by transcriptome analysis. Methods: We recruited 33 patients with IIM who were separated into the following groups: 15 patients with active disease at onset and 18 with inactive disease under treatment. All patients were positive for MSAs: anti–melanoma differentiation‐associated gene 5 (MDA5) antibody (Ab) in 10 patients, anti‐Mi‐2 Ab in 7, and anti‐aminoacyl‐transfer RNA synthetase (ARS) Ab in 16. The patients were compared with 33 healthy controls. Twenty‐four immune cell types sorted from peripheral blood were analyzed by flow cytometry, RNA sequencing, and differentially expressed gene analysis combined with pathway analysis. Results: The frequencies of memory B cell types were significantly decreased in active patients, and the frequency of plasmablasts was prominently increased in active patients with anti‐MDA5 Ab in comparison with healthy controls. The expression of type I interferon (IFN)‐stimulated genes of all immune cell types was increased in the active, but not inactive, patients. Endoplasmic reticulum stress‐related genes in all IIM memory B cells and oxidative phosphorylation‐related genes in inactive IIM double negative B cells were also increased, suggesting prominent B cell activation in IIM. Furthermore, active patients with anti‐MDA5 Ab, anti‐Mi‐2 Ab, or anti‐ARS Ab were distinguished by IFN‐stimulated and oxidative phosphorylation‐related gene expression in plasmablasts. Conclusion: Unique gene expression patterns in patients with IIM with different disease activity levels and MSA types suggest different pathophysiologies. Especially, B cells may contribute to common and MSA‐specific immunological pathways in IIM. [ABSTRACT FROM AUTHOR]

Genetic studies have revealed many variant loci that are associated with immune-mediated diseases. To elucidate the disease pathogenesis, it is essential to understand the function of these variants, especially under disease-associated conditions. Here, we performed a large-scale immune cell gene-expression analysis, together with whole-genome sequence analysis. Our dataset consists of 28 distinct immune cell subsets from 337 patients diagnosed with 10 categories of immune-mediated diseases and 79 healthy volunteers. Our dataset captured distinctive gene-expression profiles across immune cell types and diseases. Expression quantitative trait loci (eQTL) analysis revealed dynamic variations of eQTL effects in the context of immunological conditions, as well as cell types. These cell-type-specific and context-dependent eQTLs showed significant enrichment in immune disease-associated genetic variants, and they implicated the disease-relevant cell types, genes, and environment. This atlas deepens our understanding of the immunogenetic functions of disease-associated variants under in vivo disease conditions. [Display omitted] • Gene-regulation atlas of 28 immune cell types under immune-mediated diseases (IMDs) • Expression QTLs show immune cell-type and disease context specificity • Cellular pathways diversify eQTL effects under in vivo disease conditions • This atlas links IMD GWAS variants to susceptible genes, cell types, and environment The gene-regulation atlas of 28 immune cell types was constructed with immune-mediated disease patient samples and shows the dynamics of gene regulation depending on cell types and immunological conditions. [ABSTRACT FROM AUTHOR]