The purpose of this study was to elucidate the mechanism of action of baricitinib on Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling, which involves in human innate and adaptive immune system. The effects of baricitinib were evaluated using human monocyte-derived dendritic cells (MoDCs), plasmacytoid dendritic cells (pDCs), B cells, and T cells. Baricitinib concentration-dependently suppressed the expression of CD80/CD86 on MoDCs and the production of type-I interferon (IFN) by pDCs. Baricitinib also suppressed the differentiation of human B cells into plasmablasts by B cell receptor and type-I IFN stimuli and inhibited the production of interleukin (IL)-6 from B cells. Human CD4+ T cells proliferated after T cell receptor stimulation with anti-CD3 and anti-CD28 antibody; however, such proliferation was suppressed by baricitinib in a concentration-dependent manner. In addition, baricitinib inhibited Th1 differentiation after IL-12 stimulation and Th17 differentiation by TGF-β1, IL-6, IL-1β, and IL-23 stimulation. Tofacitinib showed similar effects in these experiments. In naive CD4+ T cells, IFN-α and IFN-γ induced phosphorylation of STAT1, which was inhibited by baricitinib and tofacitinib. Furthermore, IL-6-induced phosphorylation of STAT1 and STAT3 was also inhibited by JAK inhibitors. In conclusion, the results indicated that baricitinib suppresses the differentiation of plasmablasts, Th1 and Th17 cells, as well as innate immunity, such as the T cell stimulatory capacity of dendritic cells. Thus, JAK inhibitors can be potentially clinically effective not only in rheumatoid arthritis but other immune-related diseases.

Objective. Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into chondrocytes. Articular cartilage contains MSC-like chondroprogenitor cells, which suggests their involvement in the maintenance of cartilage homeostasis by a self-repair mechanism. Interleukin-6 (IL-6) is a cytokine with a wide range of physiologic functions, which are produced by MSCs in a steady manner and in large quantities. The purpose of this study was to investigate the involvement of IL-6 signaling in MSC differentiation into chondrocytes.Methods. Human bone marrow-derived MSCs were cultured using a pellet culture system in medium containing transforming growth factor b3. Chondrogenic differentiation was detected by cartilage matrix accumulation and chondrogenic marker gene expression.Results. IL-6 was detected at a high concentration in culture supernatants during chondrogenic differentiation. The expression of the IL-6 receptor (IL-6R) was significantly increased, accompanied by markedly increased phosphorylation and expression of STAT-3. Addition of IL-6 and soluble IL-6R (sIL-6R) to the chondrogenic culture resulted in concentration-dependent increases in cartilage matrix accumulation and cartilage marker gene expression (type II collagen/aggrecan/type X collagen). Phosphorylation of the master transcription factor SOX9 was enhanced upon addition of IL-6 and sIL-6R. STAT-3 knockdown suppressed chondrogenic differentiation. IL-6 and the MSC markers CD166 and nestin were colocalized in macroscopically normal human cartilage taken from the lateral femoral compartment of knees with medial tibiofemoral osteoarthritis.Conclusion. During differentiation of human MSCs into chondrocytes, the activation of IL-6/STAT-3 signaling positively regulated chondrogenic differentiation. The presence of IL-6 around MSC-like cells in the cartilage tissue was identified, suggesting that IL-6 contributes to homeostasis and cartilage self-repair by promoting chondrogenic differentiation.Articular cartilage is a structurally unique tissue, lacking blood, lymph vessels, and nerves, and it is considered to be in a low-nutrient, low-oxygen environment because of its dependency on nutrient and oxygen supplies primarily from the synovial fluid. Chondrocytes scattered in the cartilage matrix show virtually no proliferative capacity, and it has not been fully elucidated how homeostasis of cartilage tissue is maintained (1). Cartilage was once considered to consist of

Our study indicates that patients with active SLE can be divided into 3 subgroups based on T cell heterogeneity. Further immunophenotyping studies should help elucidate the pathogenesis of SLE and provide important information for the development of new therapies.

No abstract

Our findings suggest that IL-12-mediated co-activation of STAT1 and STAT4 alters histone modification, resulting in differentiation of Tfh-Th1-like cells that are characteristically expanded in patients with SLE. This could be one of the underlying mechanisms responsible for expansion of Tfh-Th1-like cells and potentially helpful towards development of cell-specific treatment for SLE.

T helper (Th) cells can differentiate into functionally distinct subsets and play a pivotal role in inflammatory and autoimmune diseases such as rheumatoid arthritis (RA). Th22 cells have been identified as a new subset secreting interleukin (IL)-22. Although elevated levels of IL-22 in the synovial fluids of RA patients were reported, its pathological roles remain unclear. Here, we demonstrated that IL-22 was characteristically produced from CD3+CD4+CC-chemokine receptor (CCR)4+CCR6+CCR10+ cells and their ability of the production of IL-22 markedly exceeded that of other Th subsets and the subset, thereby, designated Th22 cells. Th22 cells were efficiently induced by the stimulation with tumor necrosis factor-α, IL-6, and IL-1β. Th22 cells were markedly infiltrated in synovial tissue in patients with active RA, but not in patients with osteoarthritis (OA). CCL17, CCL20, and CCL28, which are chemokine ligands of CCR4, CCR6, and CCR10, respectively, were abundantly expressed in RA synovial tissue compared to OA. By in vitro Trans-well migration assay, Th22 cells efficiently migrated toward CCL28. Co-culture of Th22 cells, which were sorted from peripheral blood, with monocytes in the presence of macrophage colony-stimulating factor and receptor activator of nuclear factor (NF)-κB ligand induced osteoclasts formation more efficiently than that of either Th1 cells or Th17 cells. Furthermore, IL-22 markedly augmented osteoclast differentiation by promoting nuclear factor of activated T cells c1 expression in CD14+ monocytes. Contrarily, the addition of IFN-γ to the culture significantly decreased osteoclasts number, whereas IL-17 had marginal effects. IL-22 neutralizing antibody inhibited osteoclast formation in the co-culture of Th22 cells with CD14+ monocytes. Collectively, the results indicated that Th22 cells, which co-express chemokine receptors CCR4, CCR6, and CCR10, possess strong potency of tissue migration and accumulate into inflamed synovial tissues where the ligands such as CCL28 are highly expressed. Thus, Th22 cells have the capacity to promote osteoclast differentiation through production of IL-22 and thus play a pivotal role in bone destruction in patients with RA.

B cells play a crucial role in the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE). However, the relevance of the metabolic pathway in the differentiation of human B cell subsets remains unknown. In this article, we show that the combination of CpG/TLR9 and IFN-α markedly induced the differentiation of CD27IgD unswitched memory B cells into CD27CD38 plasmablasts. The response was accompanied by mammalian target of rapamycin complex 1 (mTORC1) activation and increased lactate production, indicating a shift to glycolysis. However, CpG alone induced the differentiation of unswitched memory B cells into CD27IgD memory B cells with high cytokine production, but such differentiation was suppressed by IFN-α. AMP-activated protein kinase activation enhanced the differentiation to CD27IgD B cells, but it attenuated mTORC1 activation and differentiation into plasmablasts. High mTORC1 activation was noted in CD19 B cells of patients with SLE and correlated with plasmablast differentiation and disease activity. Taken together, differential metabolic reprogramming commits the differentiation of human unswitched memory B cells into plasmablasts (the combination of CpG and IFN-α amplifies mTORC1-glycolysis pathways) or CD27IgD memory B cells (CpG alone amplifies the AMP-activated protein kinase pathway). The former metabolic pathway may play a pivotal role in SLE.

Objectives: Aberrant and persistent production of interferon-α (IFN-α) by plasmacytoid dendritic cells (pDCs) is known to play a key role in the pathogenesis of systemic lupus erythematosus (SLE). To assess the precise function of pDCs in SLE patients, we investigated the differential regulation of Toll-like receptor 7 (TLR7) and TLR9 responses during IFN-α production by pDCs.Methods: Peripheral blood mononuclear cells (PBMCs) in SLE patients without hydroxychloroquine treatment, rheumatoid arthritis patients and heathy controls were stimulated with TLR7 and TLR9 agonists. To investigate the priming effect by cytokines, PBMCs from healthy controls were pre-treated with various cytokines and stimulated with TLR7 and TLR9 agonists. The IFN-α production in pDCs was detected by flow cytometry.Results: TLR7-mediated IFN-α production was up-regulated and correlated positively with disease activity in SLE. Conversely, TLR9-mediated IFN-α production was down-regulated. Differential regulation of TLR7/9 response in SLE was independent of TLR7 and TLR9 expression levels. Furthermore, in vitro experiments indicated that TLR7-mediated IFN-α production was up-regulated by pre-treatment with type I IFN, whereas TLR9-mediated IFN-α production was down-regulated by pre-treatment with type II IFN.Conclusions: Our study indicates the association between up-regulation of TLR7- mediated IFN-α production by pDCs and disease activity and that TLR7 and TLR9 responses were reversely regulated on pDCs in SLE patients. Thus, type I IFN and TLR7-mediated IFN-α production were involved in a vicious cycle, causing hyper production of IFN-α by pDCs during the pathogenic processes of SLE.