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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]

Objectives We evaluated flow-cytometric and transcriptome features of peripheral blood immune cells from early-phase (disease duration <5 years) SSc in comparison with late-phase SSc. Methods Fifty Japanese patients with SSc (12 early SSc cases and 38 late SSc cases) and 50 age- and sex-matched healthy controls were enrolled. A comparison of flow-cytometric subset proportions and RNA-sequencing of 24 peripheral blood immune cell subsets was performed. We evaluated differentially expressed genes (DEGs), characterized the co-expressed gene modules, and estimated the composition of subpopulations by deconvolution based on single-cell RNA-sequencing data. As a disease control, idiopathic inflammatory myositis (IIM) patients were also evaluated. Results Analysing the data from early and late SSc, fraction II effector regulatory T cell (Fr. II eTreg) genes showed a remarkable differential gene expression, enriched for genes related to oxidative phosphorylation. Although the flow-cytometric proportion of Fr. II eTregs was not changed in early SSc, deconvolution indicated expansion of the activated subpopulation. Co-expressed gene modules of Fr. II eTregs demonstrated enrichment of the DEGs of early SSc and correlation with the proportion of the activated subpopulation. These results suggested that DEGs in Fr. II eTregs from patients with early SSc were closely associated with the increased proportion of the activated subpopulation. Similar dysregulation of Fr. II eTregs was also observed in data from patients with early IIM. Conclusions RNA-seq of immune cells indicated the dysregulation of Fr. II eTregs in early SSc with increased proportion of the activated subpopulation. [ABSTRACT FROM AUTHOR]