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Threonyl-tRNA synthetase (TRS) is an aminoacyl-tRNA synthetase that catalyzes the aminoacylation of tRNA by transferring threonine. In addition to an essential role in translation, TRS was extracellularly detected in autoimmune diseases and also exhibited pro-angiogenetic activity. TRS is reported to be secreted into the extracellular space when vascular endothelial cells encounter tumor necrosis factor-α. As T helper (Th) type 1 response and IFN-γ levels are associated with autoimmunity and angiogenesis, in this study, we investigated the effects of TRS on dendritic cell (DC) activation and CD4 T cell polarization. TRS-treated DCs exhibited up-regulated expression of activation-related cell-surface molecules, including CD40, CD80, CD86, and MHC class II. Treatment of DCs with TRS resulted in a significant increase of IL-12 production. TRS triggered nuclear translocation of the NF-κB p65 subunit along with the degradation of IκB proteins and the phosphorylation of MAPKs in DCs. Additionally, MAPK inhibitors markedly recovered the degradation of IκB proteins and the increased IL-12 production in TRS-treated DCs, suggesting the involvement of MAPKs as the upstream regulators of NF-κB in TRS-induced DC maturation and activation. Importantly, TRS-stimulated DCs significantly increased the populations of IFN-γ + CD4 T cells, and the levels of IFN-γ when co-cultured with CD4 + T cells. The addition of a neutralizing anti-IL-12 mAb to the cell cultures of TRS-treated DCs and CD4 + T cells resulted in decreased IFN-γ production, indicating that TRS-stimulated DCs may enhance the Th1 response through DC-derived IL-12. Injection of OT-II mice with OVA-pulsed, TRS-treated DCs also enhanced Ag-specific Th1 responses in vivo . Importantly, injection with TRS-treated DC exhibited increased populations of IFN-γ + -CD4 + and -CD8 + T cells as well as secretion level of IFN-γ, resulting in viral clearance and increased survival periods in mice infected with influenza A virus (IAV), as the Th1 response is associated with the enhanced cellular immunity, including anti-viral activity. Taken together, these results indicate that TRS promotes the maturation and activation of DCs, DC-mediated Th1 responses, and anti-viral effect on IAV infection., (Copyright © 2020 Jung, Park, Cho, Jung, Cho and Kim.)

In addition to essential roles in protein synthesis, lysyl-tRNA synthetase (KRS) is secreted to trigger a proinflammatory function that induces macrophage activation and TNF-α secretion. KRS has been associated with autoimmune diseases such as polymyositis and dermatomyositis. In this study, we investigated the immunomodulatory effects of KRS on bone marrow-derived dendritic cells (DCs) of C57BL/6 mice and subsequent polarization of Th cells and analyzed the underlying mechanisms. KRS-treated DCs increased the expression of cell surface molecules and proinflammatory cytokines associated with DC maturation and activation. Especially, KRS treatment significantly increased production of IL-12, a Th1-polarizing cytokine, in DCs. KRS triggered the nuclear translocation of the NF-κB p65 subunit along with the degradation of IκB proteins and the phosphorylation of MAPKs in DCs. Additionally, JNK, p38, and ERK inhibitors markedly recovered the degradation of IκB proteins, suggesting the involvement of MAPKs as the upstream regulators of NF-κB in the KRS-induced DC maturation and activation. Importantly, KRS-treated DCs strongly increased the differentiation of Th1 cells when cocultured with CD4 + T cells. The addition of anti-IL-12-neutralizing Ab abolished the secretion of IFN-γ in the coculture, indicating that KRS induces Th1 cell response via DC-derived IL-12. Moreover, KRS enhanced the OVA-specific Th1 cell polarization in vivo following the adoptive transfer of OVA-pulsed DCs. Taken together, these results indicated that KRS effectively induced the maturation and activation of DCs through MAPKs/NF-κB-signaling pathways and favored DC-mediated Th1 cell response., (Copyright © 2018 by The American Association of Immunologists, Inc.)

A flavonoid Astragalin (kaempferol-3- O -β-d-glucopyranoside, Ast) has several biological activities including anti-oxidant, anti-HIV, and anti-allergic effects. Nonetheless, its insolubility in hydrophilic solvents imposes restrictions on its therapeutic applications. In this study, we investigated the effects of water-soluble astragalin-galactoside (kaempferol-3- O -β-d-isomaltotrioside, Ast-Gal) on murine bone marrow-derived dendritic cell (DC) maturation and T helper (Th) cell-mediated immune responses. Ast-Gal significantly increased maturation and activation of DCs through the upregulation of surface markers, such as cluster of differentiation (CD)80, CD86, and Major histocompatibility complex (MHC) II in a dose-dependent manner, while Ast had little effects. Additionally, Ast-Gal-treated DCs markedly secreted immune-stimulating cytokines such as interleukin (IL)-1β, IL-6, and IL-12. Importantly, Ast-Gal strongly increased expression of IL-12, a polarizing cytokine of Th1 cells. In a co-culture system of DCs and CD4⁺ T cells, Ast-Gal-treated DCs preferentially differentiates naïve CD4⁺ T cells into Th1 cells. The addition of neutralizing IL-12 monoclonal antibody (mAb) to cultures of Ast-Gal-treated DCs and CD4⁺ T cells significantly decreased interferon (IFN)-γ production, thereby indicating that Ast-Gal-stimulated DCs enhance the Th1 response through IL-12 production by DCs. Injection with Ast-Gal-treated DCs in mice increased IFN-γ-secreting Th1 cell population. Collectively, these findings indicate that hydrophilically modified astragalin can enhance Th1-mediated immune responses via DCs and point to a possible application of water-soluble astragalin-galactoside as an immune adjuvant.

Vibrio vulnificus (V. vulnificus) is a gram-negative bacterium, which causes life-threatening septicemia and gastroenteritis through the consumption of contaminated seafood or wound infection. In addition, V. vulnificus infection is known to stimulate the production of several pro-inflammatory cytokines, which are associated with inflammatory responses mediated predominantly by dendritic cells (DCs), functioning as antigen-presenting cells. The present study aimed to investigate whether V. vulnificus infection induced the maturation and activation of murine DCs, which have the ability to polarize T helper (Th) cells into Th17 cells. Dysregulated Th17 cell responses are known to cause tissue damage, promoting the penetration of pathogens; however, Th17 cells are also involved in host defense against infection. Infection with V. vulnificus significantly increased the expression of cell surface molecules, including CD40, CD80 and major histocompatibility complex class II, leading to the maturation and activation of DCs. In the present study, the analysis of the cytokine profiles of DCs upon infection with V. vulnificus revealed the preferential production of interleukin-1β (IL-1β) and IL-6, through which V. vulnificus-infected DCs induced the polarization of Th17 cells when naïve CD4+ T cells were co-incubated. The reduction of Th17 cell generation through the use of anti-IL-6 neutralizing antibodies indicated that the Th17-polarizing capacity of V. vulnificus was predominantly dependent on DC-derived IL-6. The in vivo administration of V. vulnificus-infected DCs consistently increased the Th17 cell population in the lymph nodes of mice. Finally, the oral administration of V. vulnificus in mice also increased Th17 cell responses in the lamina propria of the small intestine. These results collectively demonstrated that V. vulnificus induced inflammatory Th17 cell responses via DCs, which may be associated with the immunopathological effects caused by V. vulnificus infection.

IL-33 is associated with a variety of autoimmune diseases, such as sclerosis, inflammatory bowel disease, and rheumatoid arthritis. Although IL-33 is mainly involved in the induction of Th2 cells, however, the relationship between IL-33 and Th17 cells is still largely unknown. In this study, we investigated the effects of IL-33 on DC-mediated CD4 + T cell activation and Th17 cell differentiation because DCs are essential cells for presenting self-antigens to CD4 + T cells in autoimmune disease conditions. OT-II mice were injected with IL-33-treated DCs or untreated DCs that were primed by OVA 323-339 peptide, and their Th17 cell responses were compared. Th17 cell population and IL-17 expression levels were significantly increased in draining lymph nodes of mice injected with IL-33-treated DCs, compared with those in mice injected with untreated DCs. IL-33 treatment maturated DCs to present self-antigens and to increase production of proinflammatory cytokines such as IL-1β and IL-6, which have a crucial role in Th17 cell differentiation. We found that the IL-33-matured DCs enhanced the expression of an early T cell activation marker (CD69) and the Th17 master transcription factor (RORγt), but IL-33 did not directly affect CD4 + T cell differentiation or increase Th17 polarization. Notably, neutralizing IL-1β and/or IL-6 significantly decreased IL-17 expression levels and Th17 cell population which were increased by the coculture of CD4 + T cells with IL-33-matured DCs, indicating that IL-33 may induce Th17 cell responses via IL-1β and IL-6 derived from IL-33-matured DCs., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Interleukin (IL)-32 has been associated with a variety of inflammatory diseases including rheumatoid arthritis, vasculitis and Crohn's disease. We have previously reported that IL-32γ, the IL-32 isoform with the highest biological activity, could act as an immune modulator through regulation of dendritic cell (DC) functions in immune responses. Cell locomotion is crucial for induction of an effective immune response. In this study, we investigated the effect and underlying mechanisms of IL-32γ on recruitment of T cells. IL-32γ upregulated the expression of several chemokines including CCL2, CCL4, and CCL5 in the DCs. In particular, IL-32γ significantly increased CCL5 expression in a dose-dependent manner. Treatment with JNK and NF-κB inhibitors suppressed IL-32γ-induced CCL5 expression in DCs, indicating that IL-32γ induced CCL5 production through the JNK and NF-κB pathways. Furthermore, supernatants from IL-32γ-treated DCs showed chemotactic activities controlling migration of activated CD4(+) and CD8(+) T cells, and these activities were suppressed by addition of neutralizing anti-CCL5 antibody. These results show that IL-32γ effectively promotes migration of activated T cells via CCL5 production in DCs. The chemotactic potential of IL-32γ may explain the pro-inflammatory effects of IL-32 and the pathologic role of IL-32 in immune disorders such as rheumatoid arthritis., (Copyright © 2014 Elsevier Inc. All rights reserved.)

IL-12 and IL-18 are cytokines which are mainly secreted by endothelial cells and monocytes including dendritic cells. The well-known effects of IL-12 and IL-18 in the protection against bacteria and virus infection as well as tumor development are associated with their characteristics in synergistically driving the development of T helper type 1 (Th1) cells and inducing IFN-γ production. In this study, we compared the knockout effects of IL-12 and/or IL-18 genes on phenotypes and functional capabilities of dendritic cells (DCs) including their ability to polarize naive CD4(+) T cells. The expression levels of surface molecules such as MHC II, CD80, CD86 and ICOSL, and endocytic capacity were not significantly differences between DCs of wild type (WT) mice and double knockout (DKO) mice of IL-12p40 and IL-18. Additionally, DCs lacking IL-12p40 and/or IL-18 genes were equivalently efficient in inducing T cell proliferation, compared with the WT-DCs. Interestingly, IL-10 production significantly decreased in DKO-DCs, while production of other inflammation-related cytokines were unaffected in WT-DCs and DKO-DCs. Importantly, IL-12p40(-/-)-DCs and DKO-DCs severely impaired the ability to induce IFN-γ and IL-17 production from CD4(+) T cells. IL-18(-/-)-DCs also moderately decreased IL-17 production and IL-17-expressing CD4(+) T cells when co-cultured with CD4(+) T cells, demonstrating the involvement of IL-18 in driving IL-17 differentiation. Taken together, these results suggest the principal contribution of IL-12p40 in inducing Th1 and Th17 polarization, regardless of similar surface phenotypes of DCs., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Isoflavones are ubiquitous compounds in foods and in the environment in general. Daidzein and genistein, the best known of isoflavones, are structurally similar to 17β-estradiol and known to exert estrogenic effects. They also evidence a broad variety of biological properties, including antioxidant, anti-carcinogenic, anti-atherogenic and anti-osteoporotic activities. Previously, daidzein was reported to increase the phagocytic activity of peritoneal macrophages and splenocyte proliferation, and to inhibit nitric oxide (NO) production in macrophages. However, its potential impacts on immune response in dendritic cells (DCs), antigen-presenting cells that link innate and adaptive immunity, have yet to be clearly elucidated. In this study, we evaluated the effects of isoflavones on the maturation and activation of DCs. Isoflavones (formononetin, daidzein, equol, biochanin A, genistein) were found to differentially affect the expression of CD86, a costimulatory molecule, on lipopolysaccharide (LPS)-stimulated DCs. In particular, daidzein significantly and dose-dependently inhibited the expression levels of maturation-associated cell surface markers including CD40, costimulatory molecules (CD80, CD86), and major histocompatibility complex class II (I-A(b)) molecule on LPS-stimulated DCs. Daidzein also suppressed pro-inflammatory cytokine production such as IL-12p40, IL-6 and TNF-α, whereas it didn't affect IL-10 and IL-1β expression. Furthermore, daidzein enhanced endocytosis and inhibited the allo-stimulatory ability of LPS-stimulated DCs on T cells, indicating that daidzein treatment can inhibit the functional maturation of DCs. These results demonstrate that daidzein may exhibit immunosuppressive activity by inhibiting the maturation and activation of DCs., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Aminoacyl tRNA synthetase-interacting protein 1 (AIMP1) is a novel pleiotropic cytokine that was identified initially from Meth A-induced fibrosarcoma. It is expressed in the salivary glands, small intestine and large intestine, and is associated with the innate immune system. Previously, we demonstrated that AIMP1 might function as a regulator of innate immune responses by inducing the maturation and activation of bone-marrow-derived dendritic cells (BM-DCs). Toll-like receptors (TLRs) are major pathogen-recognition receptors that are constitutively expressed on DCs. In this study, we attempted to determine whether AIMP1 is capable of regulating the expression of TLRs, and also capable of affecting the TLR-mediated activation of DCs. Expression of TLR1, -2, -3 and -7 was highly induced by AIMP1 treatment in BM-DCs, whereas the expression of other TLRs was either down-regulated or remained unchanged. In particular, the expression of the TLR2 protein was up-regulated by AIMP1 in a time-dependent and dose-dependent manner, and was suppressed upon the addition of BAY11-7082, an inhibitor of nuclear factor-κB. AIMP1 was also shown to increase nuclear factor-κB binding activity. Importantly, AIMP1 enhanced the production of interleukin-6 and interleukin-12, and the expression of co-stimulatory molecules on BM-DCs when combined with lipoteichoic acid or Pam3Cys, two well-known TLR2 agonists. Collectively, these results demonstrate that the AIMP1 protein enhances TLR2-mediated immune responses via the up-regulation of TLR2 expression., (© 2011 The Authors. Immunology © 2011 Blackwell Publishing Ltd.)

IL-32, a newly described multifunctional cytokine, has been associated with a variety of inflammatory diseases, including rheumatoid arthritis, vasculitis, and Crohn's disease. In this study, we investigated the immunomodulatory effects of IL-32γ on bone marrow-derived dendritic cell (DC)-driven Th responses and analyzed the underlying signaling events. IL-32γ-treated DCs exhibited upregulated expression of cell-surface molecules and proinflammatory cytokines associated with DC maturation and activation. In particular, IL-32γ treatment significantly increased production of IL-12 and IL-6 in DCs, which are known as Th1- and Th17-polarizing cytokines, respectively. This increased production was inhibited by the addition of specific inhibitors of the activities of phospholipase C (PLC), JNK, and NF-κB. IL-32γ treatment increased the phosphorylation of JNK and the degradation of both IκBα and IκBβ in DCs, as well as NF-κB binding activity to the κB site. The PLC inhibitor suppressed NF-κB DNA binding activity and JNK phosphorylation increased by IL-32γ treatment, thereby indicating that IL-32γ induced IL-12 and IL-6 production in DCs via a PLC/JNK/NF-κB signaling pathway. Importantly, IL-32γ-stimulated DCs significantly induced both Th1 and Th17 responses when cocultured with CD4(+) T cells. The addition of a neutralizing anti-IL-12 mAb abolished the secretion of IFN-γ in a dose-dependent manner; additionally, the blockage of IL-1β and IL-6, but not of IL-21 or IL-23p19, profoundly inhibited IL-32γ-induced IL-17 production. These results demonstrated that IL-32γ could effectively induce the maturation and activation of immature DCs, leading to enhanced Th1 and Th17 responses as the result of increased IL-12 and IL-6 production in DCs.

AIMP1 (ARS-interacting multifunctional protein 1), previously known as p43, was initially identified as a factor associated with a macromolecular tRNA synthetase complex. Recently, we demonstrated that AIMP1 is also secreted and acts as a novel pleiotropic cytokine. In this study, we investigated whether AIMP1 induces the activation and maturation of murine bone marrow-derived dendritic cells (DCs). AIMP1-treated DCs exhibited up-regulated expression of cell-surface molecules, including CD40, CD86, and MHC class II. Additionally, microarray analysis and RT-PCR determinations indicated that the expression of known DC maturation genes also increased significantly following treatment with AIMP1. Treatment of DCs with AIMP1 resulted in a significant increase in IL-12 production and Ag-presenting capability, and it also stimulated the proliferation of allogeneic T cells. Importantly, AIMP1-treated DCs induced activation of Ag-specific Th type 1 (Th1) cells in vitro and in vivo. AIMP1-stimulated DCs significantly enhanced the IFN-gamma production of cocultured CD4+ T cells. Immunization of mice with keyhole limpet hemocyanin-pulsed AIMP1 DCs efficiently led to Ag-specific Th1 cell responses, as determined by flow cytometry and ELISA. The addition of a neutralizing anti-IL-12 mAb to the cell cultures that had been treated with AIMP1 resulted in the decreased production of IFN-gamma, thereby indicating that AIMP1-stimulated DCs may enhance the Th1 response through increased production of IL-12 by APCs. Taken together, these results indicate that AIMP1 protein induces the maturation and activation of DCs, which skew the immune response toward a Th1 response.

T helper type 17 (Th17) cells are a subset of pro-inflammatory T helper cells that mediate host defense and pathological inflammation. We have previously reported that host dendritic cells (DCs) infected with Vibrio vulnificus induce Th17 responses through the production of several pro-inflammatory cytokines, including interleukin (IL)-1β and IL-6. V. vulnificus produces RTX toxin (RtxA), an important virulence factor that determines successful pathophysiology. In this study, we investigated the involvement of RtxA from V. vulnificus in Th17 cell induction through the activation and maturation of DCs. The increased expression of the DC surface marker CD40 caused by V. vulnificus wild-type infection was reduced by rtxA gene mutation in V. vulnificus. The mRNA and protein levels of Th17 polarization-related cytokines also decreased in V. vulnificus rtxA mutant-infected DCs. In addition, the co-culture of Th cells and DCs infected with rtxA mutant V. vulnificus resulted in reduction in DC-mediated Th17 responses. Th17 cell responses in the small intestinal lamina propria decreased in mice inoculated with V. vulnificus rtxA mutant as compared to those inoculated with the wild-type strain. These decreases in DC maturation, Th17-polarizing cytokine secretion, and Th17 responses attributed to rtxA mutation were restored following infection with the rtxA revertant strain. Furthermore, the mutation in the hlyU gene encoding the activator of rtxA1 gene reproduced the results observed with rtxA mutation. Taken together, V. vulnificus , by means of RtxA, induces inflammatory Th17 responses, which may be associated with adaptive responses of the host against V. vulnificus infection. [ABSTRACT FROM AUTHOR]