B cell dysfunction and inflammatory cytokine over‐production participate in the pathogenesis of rheumatoid arthritis (RA). Here we compared peripheral B cell homeostasis and immune functions between RA patients and healthy controls (HC) and explored vital signaling pathways involved in altered RA B cells. We found that RA patients showed significantly decreased frequencies of peripheral CD19+CD27+CD24high regulatory B (Breg) cells but increased frequencies of CD19+CD27+CD38high plasmablasts and CD19+CD138+ plasma cells, and higher levels of serum immunoglobulin (Ig)M and IgG. Compared to HC peripheral B cells, RA peripheral B cells had more increased proliferation and higher expression of activation markers. Importantly, our results showed that RA peripheral B cells displayed the mTOR signaling pathway to be more activated, and inhibition of mTOR could restore RA B cell homeostasis and functions. RA serum‐treated B cells exhibited more increased expressions of mTOR, which could be restored with the addition of anti‐interleukin (IL)‐27 neutralizing antibody. Serum IL‐27 levels were significantly increased in RA patients and positively correlated with disease activity, the frequencies of plasma cells and the levels of autoantibodies. In vitro, IL‐27 notably promoted immune dysfunction of RA B cells, which were inhibited by anti‐IL‐27 neutralizing antibody. Also, the mTOR pathway was more activated in IL‐27‐treated RA B cells, and mTOR inhibition apparently reversed abnormalities of RA B cells mediated by IL‐27. These results suggest that increased serum IL‐27 levels could promote peripheral B cell dysfunction in RA patients via activating the mTOR signaling pathway. Thus, IL‐27 may play a pro‐pathogenic role in the development of RA, and antagonizing IL‐27 could be a novel therapy strategy for RA.

Background Systemic lupus erythematosus (SLE) is characterized by loss of immune tolerance and imbalance of immune cell subsets. Natural killer (NK) cells contribute to regulate both the innate and adaptive immune response. In this study, we aimed to detect alterations of peripheral NK cells and explore intrinsic mechanisms involving in NK cell abnormality in SLE. Methods Blood samples from healthy controls (HCs) and patients with SLE and rheumatoid arthritis (RA) were collected. The NK count, NK subsets (CD56bright, CD56dimCD57−, and CD56dimCD57+), phenotypes, and apoptosis were evaluated with flow cytometer. Mitochondrial reactive oxygen species (mtROS) and total ROS levels were detected with MitoSOX Red and DCFH-DA staining respectively. Published data (GSE63829 and GSE23695) from Gene Expression Omnibus (GEO) was analyzed by Gene Set Enrichment Analysis (GSEA). Results Total peripheral NK count was down-regulated in untreated SLE patients in comparison to that in untreated RA patients and HCs. SLE patients exhibited a selective reduction in peripheral CD56dimCD57+ NK cell proportion, which was negatively associated with disease activity and positively correlated with levels of complement(C)3 and C4. Compared with HCs, peripheral CD56dimCD57+ NK cells from SLE patients exhibited altered phenotypes, increased endogenous apoptosis and higher levels of mtROS and ROS. In addition, when treated with hydrogen peroxide (H2O2), peripheral CD56dimCD57+ NK cell subset was more prone to undergo apoptosis than CD56dimCD57− NK cells. Furthermore, this NK cell subset from SLE patients exhibited impaired cytotoxicity in response to activated CD4+ T cells in vitro. Conclusion Our study demonstrated a selective loss of mature CD56dimCD57+ NK cell subset in SLE patients, which may caused by preferential apoptosis of this subset under increased oxidative stress in SLE. The attenuated in vitro cytotoxicity of CD56dimCD57+ NK cells may contribute to the impaired ability of eliminating pathogenic CD4+ T cells in SLE.

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Background: Systemic lupus erythematosus(SLE) is characterized by loss of immune tolerance and imbalance of immune cell subsets. NK cells contribute to regulate both the innate and adaptive immune response. In this study, we aimed to detect peripheral NK cell subsets in SLE patients, investigate their cytotoxic effect on activated CD4+ T cells, and explore intrinsic mechanisms contributing to NK cell abnormality.Methods: Blood samples from healthy controls(HCs) and patients with SLE and rheumatoid arthritis(RA) were collected. The NK count, NK subsets(CD56bright , CD56dimCD57- , and CD56dimCD57+), phenotypes, along with apoptosis were analysed by flow cytometry. The t-stochastic neighbor embedding (tSNE) analysis of lymphocytes based on immune cells flow cytometry markers was performed. Mitochondrial reactive oxygen species(mtROS) and total ROS levels in NK cells were detected by MitoSOX Red and DCFH-DA staining respectively. Published data(GSE63829 and GSE23695) from Gene Expression Omnibus(GEO) was analyzed by Gene Set Enrichment Analysis(GSEA).Results: NK count was down-regulated in untreated SLE patients in comparison to untreated RA patients or HCs and the count was negatively correlated with disease activity. SLE patients exhibited a selective reduction in CD56dimCD57+ NK cell proportion, which was negatively correlated with Systemic Lupus Erythematosus Disease Activity Index(SLEDAI) and positively correlated with complement C3 and C4. CD56dimCD57+NK cells exhibited increased cytotoxic effect on activated CD4+ T cells relative to CD56dimCD57- NK cells. Compared with HCs, CD56dimCD57+ NK cells in SLE patients exhibited impaired cytotoxic function, increased apoptosis and higher levels of both mtROS and ROS. GSEA analysis indicated that ROS pathway was significantly enriched in NK cells from lupus. Compared with CD56dimCD57- NK cells in SLE patients, CD56dimCD57+ NK cells showed higher levels of oxidative stress and apoptosis. Furthermore, oxidative stress levels were negatively correlated with perforin expression and positively correlated with apoptosis. CD56dimCD57+ NK cells were more prone to undergo apoptosis when exposed to ROS in vitro. Conclusion: Beyond the reduced NK cell number, our study demonstrated a selective loss of mature CD56dimCD57+ NK cell subset, which was conversely correlated with disease activity. This subset showed attenuated cytotoxic function, up-regulated endogenous apoptosis and increased oxidative stress, which might contribute to NK cell abnormality.