CD137 ligand reverse signaling has multiple functions in human dendritic cells during an adaptive immune response

T cell activation via dendritic cells (DC) is an important step in the adaptive immune response, which requires DC maturation, migration to lymph nodes and presentation of antigen to T cells. CD137 receptor expressed on activated T cells is a potent costimulatory molecule. Here, we investigated the functions of CD137 ligand (CD137L) in human monocyte-derived DC during an immune response. Cross-linking of CD137L on DC leads to cell maturation in an autocrine fashion, mostly via release of TNF-alpha. Reverse signaling of CD137L also mediates migration of DC via up-regulation of the CCR7 chemokine receptor, demonstrated by an in vivo MIP-3beta-dependent SCID mouse migration model. Finally, CD137L-activated DC induce differentiation of human T cells into potent Th1 effectors. Cocultivation of autologous T cells and CD137L-activated DC in an antigen-specific reaction leads to T cell proliferation and the release of IL-12p70 and IFN-gamma. These findings deliver new insights into the multiple effects of reverse signaling of CD137L in human DC during the initiation of an adaptive immune response, including the key features of DC maturation, migration and, ultimately, antigen-specific T cell differentiation.     

Stress‐activated dendritic cells interact with CD4+ T cells to elicit homeostatic memory

Evidence is presented that thermal or oxidizing stress‐activated DC interact with CD4⁺ T cells to induce and maintain a TCR‐independent homeostatic memory circuit. Stress‐activated DC expressed endogenous intra‐cellular and cell surface HSP70. The NF‐κB signalling pathway was activated and led to the expression of membrane‐associated IL‐15 molecules. These interacted with the IL‐15 receptor complex on CD4⁺ T cells, thus activating the Jak3 and STAT5 phosphorylation signalling pathway to induce CD40 ligand expression, T‐cell proliferation and IFN‐γ production. CD40 ligand on CD4⁺ T cells in turn re‐activated CD40 molecules on DC, inducing DC maturation and IL‐15 expression thereby maintaining the feedback circuit. The proliferating CD4⁺ T cells were characterized as CD45RA^? CD62L⁺ central memory cells, which underwent homeostatic proliferation. The circuit is independent of antigen and MHC‐class‐II‐TCR interaction as demonstrated by resistance to TCR inhibition by ZAP70 inhibitor or MHC‐class II antibodies. These findings suggest that stress can activate a DC‐CD4⁺ T‐cell interacting circuit, which may be responsible for maintaining a homeostatic antigen‐independent memory.     

Induction of Treg by monocyte‐derived DC modulated by vitamin D3 or dexamethasone: Differential role for PD‐L1

Specific therapy with modulated DC may restore immunological tolerance, thereby obviating the need for chronic immunosuppression in transplantation or autoimmunity. In this study we compared the tolerizing capacity of dexamethasone (Dex)‐ and 1α,25‐dihydroxyvitamin D3 (VD3)‐modulated DC. Treatment of monocytes with either VD3 or Dex resulted in DC with stable, semi‐mature phenotypes compared with standard DC, with intermediate levels of co‐stimulatory and MHC class II molecules, which remained unaltered after subsequent pro‐inflammatory stimulation. IL‐12p70 secretion was lost by VD3‐ and Dex‐DC, whereas IL‐10 secretion was unaffected. VD3‐DC distinctly produced large amounts of TNF‐α. Both VD3‐ and Dex‐DC possessed the capacity to convert CD4 T cells into IL‐10‐secreting Treg potently suppressing the proliferation of responder T cells. However, only Treg induced by VD3‐DC exhibited antigen specificity. VD3‐, but not Dex‐, DC expressed significant high levels of PD‐L1 (programmed death‐1 ligand), upon activation. Blockade of PD‐L1 during priming redirected T cells to produce IFN‐γ instead of IL‐10 and abolished acquisition of regulatory capacity. Our findings demonstrate that both VD3‐ and Dex‐DC possess durable but differential tolerogenic features, acting via different mechanisms. Both are potentially useful to specifically down‐regulate unwanted immune responses and induce immune tolerance. These modulated DC appear suitable as adjuvant in antigen‐specific clinical vaccination intervention strategies.     

Contribution of the PD-1 ligands/PD-1 signaling pathway to dendritic cell-mediated CD4+ T cell activation

Dendritic cells (DC) are extremely proficient inducers of naïve CD4⁺ T cell activation due to their high expression level of peptide‐MHC and an array of accessory molecules involved in cell migration, adhesion and co‐signaling, including PD‐1 ligand 1 (PD‐L1) and PD‐1 ligand 2 (PD‐L2). Whether PD‐L1 and PD‐L2 have a stimulatory or inhibitory function is a matter of debate, and could be partially dependent on the model system used. In this study we examined the role of PD‐L1 and PD‐L2 expressed by DC in naïve CD4⁺ T cell activation in a more physiologically relevant model system, using OVA‐specific T cells in combination with various levels of TCR stimulation. Overexpression of PD‐L1 or PD‐L2 by DC did not inhibit T cell proliferation, even when B7–1 and B7–2 mediated costimulation was absent, although IL‐2 production was consistently decreased. Surprisingly, blocking PD‐L1 and PD‐L2 with soluble programmed death‐1 (sPD‐1) also inhibited T cell activation, probably via reverse signaling via PD‐L1 and/or PD‐L2 into DC, leading to reduced DC maturation. This study suggests a relatively minor contribution of PD‐1 ligands in DC‐driven CD4⁺ T cell activation and provides evidence for reverse signaling by PD‐L1 and PD‐L2 into DC, resulting in a suppressive DC phenotype.     

Lipopolysaccharide-induced expression of TRAIL promotes dendritic cell differentiation

Tumour necrosis factor‐related apoptosis inducing ligand (TRAIL) is a death‐inducing cytokine whose physiological function is not well understood. Here, we show that TRAIL has a role in programming human dendritic cell (DC) differentiation. TRAIL expression was strongly induced in DCs upon stimulation with lipopolysaccharide (LPS) or Polyinosine‐polycytidylic acid (poly(I:C)) stimulation. Blockade of TRAIL with neutralizing antibody partially inhibited LPS‐induced up‐regulation of co‐stimulatory molecules and the expression of inflammatory cytokines including interleukin‐12 (IL‐12) p70. In addition, neutralization of TRAIL in LPS‐treated DCs inhibited the DC‐driven differentiation of T cells into interferon‐γ (IFN‐γ) ‐producing effectors. The effects of TRAIL neutralization in poly(I:C)‐treated DCs were similar, except that IL‐12 production and the differentiation of effector T cells into IFN‐γ producers were not inhibited. Strikingly, TRAIL stimulation alone was sufficient to induce morphological changes resembling DC maturation, up‐regulation of co‐stimulatory molecules, and enhancement of DC‐driven allogeneic T‐cell proliferation. However, TRAIL alone did not induce inflammatory cytokine production. We further show that the effects of TRAIL on DC maturation were not the result of the induction of apoptosis, but may involve p38 activation. Hence, our data demonstrate that TRAIL co‐operates with other cytokines to facilitate DC functional maturation in response to Toll‐like receptor activation.     

Autologous tolerogenic dendritic cells derived from monocytes of systemic lupus erythematosus patients and healthy donors show a stable and immunosuppressive phenotype

Systemic lupus erythematosus (SLE) is an autoimmune disease with unrestrained T‐cell and B‐cell activity towards self‐antigens. Evidence shows that apoptotic cells (ApoCells) trigger an autoreactive response against nuclear antigens in susceptible individuals. In this study, we focus on generating and characterizing tolerogenic dendritic cells (tolDCs) to restore tolerance to ApoCells. Monocyte‐derived dendritic cells (DCs) from healthy controls and patients with SLE were treated with dexamethasone and rosiglitazone to induce tolDCs. Autologous apoptotic lymphocytes generated by UV irradiation were given to tolDCs as a source of self‐antigens. Lipopolysaccharide (LPS) was used as a maturation stimulus to induce the expression of co‐stimulatory molecules and secretion of cytokines. TolDCs generated from patients with SLE showed a reduced expression of co‐stimulatory molecules after LPS stimulation compared with mature DCs. The same phenomenon was observed in tolDCs treated with ApoCells and LPS. In addition, ApoCell‐loaded tolDCs stimulated with LPS secreted lower levels of interleukin‐6 (IL‐6) and IL‐12p70 than mature DCs without differences in IL‐10 secretion. The functionality of tolDCs was assessed by their capacity to prime allogeneic T cells. TolDCs displayed suppressor properties as demonstrated by a significantly reduced capacity to induce allogeneic T‐cell proliferation and activation. ApoCell‐loaded tolDCs generated from SLE monocytes have a stable immature/tolerogenic phenotype that can modulate CD4⁺ T‐cell activation. These properties make them suitable for an antigen‐specific immunotherapy for SLE.     

Regulation of Myelopoiesis by CD137L Signaling

CD137 ligand (CD137L) has emerged as a powerful regulator of myelopoiesis that links emergency situations, such as infections, to the generation of additional myeloid cells, and to their activation and maturation. CD137L is expressed on the cell surface of hematopoietic stem and progenitor cells (HSPC) and antigen presenting cells (APC) as a transmembrane protein. The signaling of CD137L into HSPC induces their proliferation and differentiation to monocytes and macrophages, and in monocytes CD137L signaling induces differentiation to potent dendritic cells (DC). CD137L signaling is initiated by CD137 which is expressed by T cells, once they become activated. Some of these activated, CD137-expressing T cells migrate from the site of infection to the bone marrow where they interact with HSPC to induce myelopoiesis, or they induce monocyte to DC differentiation locally at the site of infection. Therapeutically, induction of CD137L signaling can be utilized to reinitiate myeloid differentiation in acute myeloid leukemia cells, and to generate potent DC for immunotherapy.     

Generation of Potent Cytotoxic T Lymphocytes Against Castration‐Resistant Prostate Cancer Cells by Dendritic Cells Loaded With Dying Allogeneic Prostate Cancer Cells

To induce a potent cytotoxic T lymphocyte (CTL) response in dendritic cell (DC)‐based immunotherapy against prostate cancer, various tumour antigens should be loaded onto DCs. The aim of this study was to establish a method of immunotherapy for castration‐resistant prostate cancer (CRPC) using prostate cancer–specific CTLs generated in vitro by DCs. Monocyte‐derived DCs from patients with CRPC were induced to mature using a standard cytokine cocktail (in IL‐1β, TNF‐α, IL‐6 and PGE₂: standard DCs, sDCs) or using an α‐type 1‐polarized DC (αDC1) cocktail (in IL‐1β, TNF‐α, IFN‐α, IFN‐γ and polyinosinic:polycytidylic acid) and loaded with the UVB‐irradiated CRPC cell line PC‐3. Antigen‐loaded DCs were evaluated by morphological and functional assays. The αDC1s significantly increased the expression of several molecules related to DC maturation, regardless of whether the αDC1s were loaded with tumour antigens or not, compared to sDCs. The αDC1s showed a higher production of interleukin‐12 both during maturation and after subsequent stimulation with CD40L, which was not significantly affected by loading with tumour antigens, as compared to standard DCs (sDCs). Prostate cancer–specific CTLs against autologous CRPC cells were successfully induced by αDC1s loaded with dying PC‐3 cells. Autologous αDC1s loaded with an allogeneic CRPC cell line can generate greater CRPC‐specific CTL responses as compared to sDCs and may provide a novel source of DC‐based vaccines that can be used for the development of immunotherapy in patients with CRPC.     

Mycobacterium bovis bacillus Calmette-Guérin-infected dendritic cells potently activate autologous T cells via a B7 and interleukin-12-dependent mechanism

Mycobacteria are potent adjuvants, can survive intracellularly and have been safely used for many years as vaccines against tuberculosis and leprosy. They are thus important potential vectors for recombinant vaccines. Many of their adjuvant properties are mediated following phagocytosis by dendritic cells (DC), which are in turn critical for priming naïve T cells. Although the maturation of DC in response to mycobacteria, such as Mycobacterium bovis bacillus Calmette–Guérin (BCG), is well described the subsequent responses of autologous T cells to mycobacterium‐infected DC remains uncharacterized. In our experiments DC infected with BCG expressed more co‐stimulatory molecules than tumour‐necrosis factor‐α (TNF‐α) ‐treated DC and stimulated more potent mixed leucocyte reactions. When autologous T cells were co‐cultured with BCG‐exposed DC they became highly activated, as determined by display of CD25, CD54 and CD71 on both CD4⁺ and CD8⁺ cells. In contrast, the response of T cells to TNF‐α‐matured DC was significantly less. Cytokine production from T cells cultured with BCG‐exposed DC was enhanced with elevated secretion of interleukin‐2 (IL‐2), IL‐10 and interferon‐γ (IFN‐γ) and was produced by both CD4⁺ and CD8⁺ lymphocytes as determined by intracellular staining. In particular, IFN‐γ secretion was increased from 50 pg/ml to 25 000 pg/ml and IL‐10 secretion increased from 20 pg/ml to 300 pg/ml in BCG‐exposed DC co‐cultures. Blocking antibodies to B7.1 and B7.2 or IL‐12 significantly reduced the secretion of IFN‐γ and reductions were also seen in the expression of CD25 and CD71 by CD4⁺ cells. These data demonstrate that mycobacterially infected DC are particularly potent activators of autologous T cells compared to TNF‐α‐exposed DC and that the resultant T cells are functionally superior.     

IL‐10 promotes homeostatic proliferation of human CD8+ memory T cells and,when produced by CD1c+ DCs,shapes naive CD8+ T‐cell priming

IL‐10 is an anti‐inflammatory cytokine that inhibits maturation and cytokine production of dendritic cells (DCs). Although mature DCs have the unique capacity to prime CD8⁺ CTL, IL‐10 can promote CTL responses. To understand these paradoxic findings, we analyzed the role of IL‐10 produced by human APC subsets in T‐cell responses. IL‐10 production was restricted to CD1c⁺ DCs and CD14⁺ monocytes. Interestingly, it was differentially regulated, since R848 induced IL‐10 in DCs, but inhibited IL‐10 in monocytes. Autocrine IL‐10 had only a weak inhibitory effect on DC maturation, cytokine production, and CTL priming with high‐affinity peptides. Nevertheless, it completely blocked cross‐priming and priming with low‐affinity peptides of a self/tumor‐antigen. IL‐10 also inhibited CD1c⁺ DC‐induced CD4⁺ T‐cell priming and enhanced Foxp3 induction, but was insufficient to induce T‐cell IL‐10 production. CD1c⁺ DC‐derived IL‐10 had also no effect on DC‐induced secondary expansions of memory CTL. However, IL‐15‐driven, TCR‐independent proliferation of memory CTL was enhanced by IL‐10. We conclude that DC‐derived IL‐10 selects high‐affinity CTL upon priming. Moreover, IL‐10 preserves established CTL memory by enhancing IL‐15‐dependent homeostatic proliferation. These combined effects on CTL priming and memory maintenance provide a plausible mechanism how IL‐10 promotes CTL responses in humans.     

Optimal stimulation for CD70 induction on human monocyte‐derived dendritic cells and the importance of CD70 in naive CD4+ T‐cell differentiation

Studies in mice have shown that CD70 on dendritic cells (DCs) is sufficient to convert T‐cell tolerance into immunity and hence induce anti‐tumour immune responses. Therefore, it is important to investigate (i) optimal stimuli to induce CD70 on human monocyte‐derived DCs (MoDCs), which are widely used for tumour immunotherapy, and (ii) the role of CD70 in functional differentiation of naive CD4⁺ and CD8⁺ T cells stimulated with MoDCs. We show that interferon‐α (IFN‐α) is a key cytokine to differentiate monocytes into DCs with the capacity to express CD70 upon maturation. CD70 expression on IFN‐α‐induced MoDCs was elicited by different categories of maturation‐inducing factors (Toll‐like receptor ligands, CD40 ligand and pro‐inflammatory mediators), among which prostaglandin E₂ was most effective. Naive T cells stimulated with MoDCs also expressed CD70. Stimulation with MoDCs promoted naive CD4⁺ T cells to acquire the ability to produce T helper type 1 and 2 cytokines in a CD70‐dependent manner. In contrast, the CD70–CD27 interaction diminished the production of an immunoregulatory cytokine IL‐10. The CD27 signal did not play a dominant role in the induction of effector molecules in naive CD8⁺ T cells during the stimulation with MoDCs. This study adds a novel function to the versatile cytokines, type I IFNs, that is, the induction of CD70 on MoDCs. CD70 promotes naive CD4⁺ T cells to acquire immunostimulatory activity through the DC–T‐cell and T‐cell–T‐cell interactions during the stimulation with MoDCs. Hence, the CD70–CD27 interaction may play an important role in inducing effective immune responses in DC‐based immunotherapy.     

Species‐dependent role of type I IFNs and IL‐12 in the CTL response induced by humanized CpG complexed with β‐glucan

CpG oligodeoxynucleotide (ODN) is one of promising nucleic acid‐based adjuvants. We recently improved its ability to enhance CD8⁺ T‐cell responses to coadministered protein antigen without conjugation or emulsion, by forming a nanoparticulate complex between CpG ODN (K3) and mushroom‐derived β‐glucan schizophyllan (SPG), namely K3‐SPG. Here, we sought to elucidate the cellular immunological mechanisms by which K3‐SPG induce such potent CD8⁺ T‐cell responses to coadministered antigen. By focusing on two DC subsets, plasmacytoid DCs and CD8α⁺ DCs, as well as the secreted cytokines, IFN‐α and IL‐12, we found that K3‐SPG strongly activates mouse plasmacytoid DCs to secrete IFN‐α and CD8α⁺ DCs to secrete IL‐12, respectively. Although a single cytokine deficiency had no impact on adjuvant effects, the lack of both type I IFN and IL‐12 in mice resulted in a significant reduction of Th1 type immune responses and CD8⁺ T‐cell responses elicited by protein vaccine model. By sharp contrast, type I IFN, but not IL‐12, was required for the production of IFN‐γ by human PBMCs as well as antigen‐specific CD8⁺ T‐cell proliferation. Taken together, K3‐SPG may overcome the species barrier for CpG ODN to enhance antigen‐specific CD8⁺ T‐cell responses despite the differential role of IL‐12 between human and mice.     

IFN‐γ stimulates CpG‐induced IL‐10 production in B cells via p38 and JNK signalling pathways

The production of IL‐10, a potent immunosuppressive cytokine, must be strictly regulated to ensure a balanced immune response. IFN‐γ, a key cytokine in multiple immune processes and pathologies, is known as an inhibitor of IL‐10 production by monocytes and macrophages, but also has some regulatory functions. In the present study, we explored the role of IFN‐γ on Toll‐like receptor (TLR)‐induced IL‐10 production in murine peritoneal and spleen cells and in human peripheral blood mononuclear cells. IFN‐γ inhibited IL‐10 production induced by TLR2, TLR3, TLR4 and TLR7/8 agonists, but stimulated IL‐10 production when cells were triggered with CpG oligodeoxynucleotides, a specific TLR9 agonist. The stimulatory effect of IFN‐γ on TLR9‐induced IL‐10 was restricted to B cells. In line with the increased IL‐10, B cells stimulated with CpG and IFN‐γ profoundly inhibited CD4 T cell proliferation. Further research into the mechanisms involved, revealed that the mitogen‐activated protein kinases p38 and JNK are essential players in this stimulatory effect, and that the phosphatase MKP1 – an inhibitor of p38 and JNK activity – is downregulated after combined stimulation with IFN‐γ and CpG. Our data may represent a novel immunoregulatory role of IFN‐γ in B cells after triggering of TLR9, by stimulating IL‐10 production.     

Interleukin-10-modulated immature dendritic cells control the proinflammatory environment in multiple sclerosis

Multiple sclerosis (MS) is a disabling, inflammatory, demyelinating disease of the central nervous system considered to be mediated by autoreactive T cells. Dendritic cells (DC), being professional antigen‐presenting cells, play a pivotal role in the decision between T‐cell activation and anergy. It has been suggested that mature DC (mDC) induce immunity, whereas immature DC (imDC) have the potential to induce tolerance. In this study, we investigated the effects of autologous imDC versus autologous mDC on lymphocytes with respect to the expression of functionally important cell‐surface molecules and production of cytokines. Our aims were to investigate whether the maturation status of DC differs between MS and healthy controls (HC) and to explore whether the effects of DC on T‐cell responses differ between MS and HC. DC were generated from adherent blood mononuclear cells from patients with MS and HC. imDC were obtained by culture with either granulocyte–macrophage colony‐stimulating factor (GM‐CSF) + interleukin‐4 (IL‐4) or GM‐CSF + IL‐4 + IL‐10. mDC were obtained by adding lipopolysaccharide to DC cultures. Upon coculture with autologous lymphocytes, mDC activated the autologous T cells as reflected by increased CD25 and cytotoxic T‐lymphocyte antigen‐4 expression on CD4⁺ T cells together with the increased production of both T helper 1 (Th1) (IL‐2 and interferon‐γ) and Th2 (IL‐10 and IL‐4) cytokines. Unmodulated naïve imDC induced the production of only IL‐4. An exposure of imDC to IL‐10 induced the production of IL‐4 as well as IL‐10 by autologous lymphocytes. We hypothesize that such imDC are important in controlling the proinflammatory environment in vivo in patients with MS.     

Sphingosine 1-phosphate interferes on the differentiation of human monocytes into competent dendritic cells

Sphingosine 1‐phosphate (S1P) is a lipidic messenger known to exert several physiological functions within the cell. We tested here whether the stimulation of human monocytes with different doses of S1P might interfere with their differentiation into competent dendritic cells (DC). Monocytes cultured with granulocyte macrophage colony stimulating factor, interleukin‐4 (IL‐4) and S1P differentiated into a DC population lacking CD1a molecules on the surface and acquired some aspects of mature DC (mDC), though in the absence of maturation stimuli. When stimulated with lipopolisaccharide (LPS), CD1a⁻ DC produce high amounts of tumour necrosis factor‐α and IL‐10, but not IL‐12. Accordingly, these CD1a⁻ DC were not capable of stimulating allogenic T lymphocytes so well as CD1a⁺ DC generated from untreated monocytes and maturated with LPS. S1P monocyte‐derived DC lost their polarizing capacity abrogating the production of γ‐interferon/IL‐4 by co‐cultured naïve CD4⁺CD45RA⁺ T cells. Our findings suggest a mechanism through which S1P can favour the development of immune‐related pathological states.     

Innate and adaptive stimulation of murine diverse NKT cells result in distinct cellular responses

Natural killer T (NKT) cells recognize glycolipids presented on CD1d. They share features of adaptive T lymphocytes and innate NK cells, and mediate immunoregulatory functions via rapid production of cytokines. Invariant (iNKT) and diverse (dNKT) NKT cell subsets are defined by their TCR. The immunological role of dNKT cells, that do not express the invariant TCRα‐chain used by iNKT cells, is less well explored than that of iNKT cells. Here, we investigated signals driving Toll‐like receptor (TLR) ligand activation of TCR‐transgenic murine dNKT cells. IFN‐γ production by dNKT cells required dendritic cells (DC), cell‐to‐cell contact and presence of TLR ligands. TLR‐stimulated DC activated dNKT cells to secrete IFN‐γ in a CD1d‐, CD80/86‐ and type I IFN‐independent manner. In contrast, a requirement for IL‐12p40, and a TLR ligand‐selective dependence on IL‐18 or IL‐15 was observed. TLR ligand/DC stimulation provoked early secretion of pro‐inflammatory cytokines by both CD62L⁺ and CD62L^? dNKT cells. However, proliferation was limited. In contrast, TCR/co‐receptor‐mediated activation resulted in proliferation and delayed production of a broader cytokine spectrum preferentially in CD62L^? dNKT cells. Thus, innate (TLR ligand/DC) and adaptive (TCR/co‐receptor) stimulation of dNKT cells resulted in distinct cellular responses that may contribute differently to the formation of immune memory.     

T‐bet protects against exacerbation of schistosome egg‐induced immunopathology by regulating Th17‐mediated inflammation

C57BL/6 mice infected with Schistosoma mansoni naturally develop mild CD4⁺ T‐cell‐mediated immunopathology characterized by small hepatic granulomas around parasite eggs. However, immunization with soluble egg Ag in CFA markedly exacerbates the lesions by inducing a potent proinflammatory environment with high levels of IFN‐γ and IL‐17, which are signature cytokines of distinct Th1‐ versus Th17‐cell lineages. To determine the relative role of these subsets in disease exacerbation, we examined mice deficient in T‐bet (T‐bet^?/?), which is required for Th1 differentiation and IFN‐γ production. We now report that immunization with soluble egg Ag in CFA caused a significantly greater enhancement of egg‐induced hepatic immunopathology in T‐bet^?/? mice compared with WT controls, and analysis of their granulomas disclosed a higher proportion of activated DC and CD4⁺ T cells, as well as a marked influx of neutrophils. The absence of IFN‐γ in the T‐bet^?/? mice correlated with a marked increase in IL‐23p19, IL‐17 and TNF‐α in granulomas and MLN. In contrast, T‐bet^?/? mice had lower levels of IL‐4, IL‐5 and IL‐10 and a reduction in FIZZ1 and FoxP3 expression, suggesting diminished regulatory activity, respectively, by alternatively activated macrophages and Treg. These findings demonstrate that T‐bet‐dependent signaling negatively regulates Th17‐mediated immunopathology in severe schistosomiasis.     

Inhibitory effects of suplatast tosilate on the differentiation and function of monocyte-derived dendritic cells from patients with asthma

Background Dendritic cells (DCs) are antigen‐presenting cells that efficiently activate T cells. Objective We examined the effects of suplatast tosilate, which prevents T‐helper type 2 responses, on the differentiation and function of monocyte‐derived DCs (moDCs). Methods DCs were differentiated in vitro from peripheral monocytes from patients with asthma by the addition of granulocyte macrophage colony‐stimulating factor and IL‐4 in the presence or absence of suplatast tosilate. Cell surface molecules (CD1a, CD14, CD80, CD83, CD86, HLA‐DR) on immature and mature DCs were analysed with flow cytometry, and the secretion of CC chemokine ligand (CCL)17 (thymus and activation‐regulated chemokine), IL‐12p70, IL‐12p40, and IL‐10 was measured with an ELISA. We also studied the proliferative responses of allogeneic CD4⁺ T cells from healthy subjects to DCs differentiated in the presence of suplatast tosilate. In addition, the production of IFN‐γ and IL‐5 by CD4⁺ T cells after coculture with untreated DCs or suplatast tosilate‐treated DCs was measured with ELISA. Results Suplatast tosilate significantly inhibited the expression of CD1a, CD80, and CD86 on immature DCs and of CD1a, CD80, CD83, and CD86 on mature DCs. Suplatast tosilate also significantly inhibited the secretion of CCL17, IL‐12p70, and IL‐12p40; however, the secretion of IL‐10 was not affected. The proliferative responses of allogeneic CD4⁺ T cells to suplatast tosilate‐treated DCs were suppressed. Moreover, suplatast tosilate‐treated DCs had an impaired capacity to stimulate CD4⁺ T cells to produce IFN‐γ and IL‐5. Conclusion Suplatast tosilate inhibits the differentiation, maturation, and function of moDCs.