Relationship of TGF‐β1 and Smad7 expression with decreased dendritic cell infiltration in liver gastrointestinal cancer metastasis

Immune responses and their modulation within the liver are critical to the outcome of liver malignancies. In late‐stage tumors, secreted TGF‐β promotes oncogenic functions and can confer tolerogenicity to some immune cells like DCs. The TGF‐β signaling pathway is involved in the control of several biological processes, including immunosurveillance. The aim of the present study was to assess CD1a⁺ and CD83⁺ DCs and to evaluate the impact of TGF‐β pathway on DCs maturation and distribution in the liver metastases from gastric and colorectal tumors. The percentage of CD83⁺ DCs in the liver tissue, surrounding metastasis and in the metastasis‐free liver was measured by flow cytometry, and TGF‐β levels were assessed in the tissue supernatant from the peritumoral liver after mononuclear cell isolation and in the sera of the same patients. CD1a⁺ and CD83⁺ DCs were observed in the tumor stroma and border. Out of 73 patients, there was cytoplasmic reactivity: of TGF‐β1 in 37 (50.7%); of Smad4 in 62 (84.9%); of Smad7 in 46 (63%), and of TGFβRII in 39 (53.4%) of the metastases. The TGF‐β1 expression in tumor cell cytoplasm correlated with low CD1a⁺ and low CD83⁺ DCs infiltration. The tissue levels of TGF‐β1, measured by ELISA in the supernatant were significantly increased in metastases than in normal liver. Using a two‐color FACS analysis, we found that the percentage of HLA‐DR⁺ CD83⁺ DCs in metastases was significantly decreased as compared with metastasis‐free liver tissue. In conclusion, the positive and negative correlations between the mediators from the TGF‐β pathway implied the existence of imbalance and suppression of this cytokine activity. The presence of increased TGF‐β expression by immunohistochemistry in tumor cells was confirmed by detection of increased TGF‐β tissue level in the supernatant from the tissue homogenate. The observation of low numbers of CD1a⁺ and CD83⁺ DCs in tumor stroma correlated with TGF‐β overexpression in tumor cells, a fact that well documents the immunosuppressive role of TGF‐β in metastasis development. The increased percentage of CD83⁺ DCs in the peritumoral tissue supposes that there could be active recruitment or local differentiation of DCs in the metastasis border, but inside the tumor the immune cells recruitment and activity are suppressed by TGF‐β and by other cytokines.     

TLR2‐activated human langerhans cells promote Th17 polarization via IL‐1β, TGF‐β and IL‐23

The cytokines IL‐6, IL‐1β, TGF‐β, and IL‐23 are considered to promote Th17 commitment. Langerhans cells (LC) represent DC in the outer skin layers of the epidermis, an environment extensively exposed to pathogenic attack. The question whether organ‐resident DC like LC can evoke Th17 immune response is still open. Our results show that upon stimulation by bacterial agonists, epidermal LC and LC‐like cells TLR2‐dependently acquire the capacity to polarize Th17 cells. In Th17 cells, expression of retinoid orphan receptor γβ was detected. To clarify if IL‐17⁺cells could arise per se by stimulated LC we did not repress Th1/Th2 driving pathways by antibodies inhibiting differentiation. In CD1c⁺/langerin⁺ monocyte‐derived LC‐like cells (MoLC), macrophage‐activating lipopeptide 2, and peptidoglycan (PGN) induced the release of the cytokines IL‐6, IL‐1β, and IL‐23. TGF‐β, a cytokine required for LC differentiation and survival, was found to be secreted constitutively. Anti‐TLR2 inhibited secretion of IL‐6, IL‐1β, and IL‐23 by MoLC, while TGF‐β was unaffected. The amount of IL‐17 and the ratio of IL‐17 to IFN‐γ expression was higher in MoLC‐ than in monocyte‐derived DC‐cocultured Th cells. Anti‐IL‐1β, ‐TGF‐β and ‐IL‐23 decreased the induction of Th17 cells. Interestingly, blockage of TLR2 on PGN‐stimulated MoLC prevented polarization of Th cells into Th17 cells. Thus, our findings indicate a role of TLR2 in eliciting Th17 immune responses in inflamed skin.     

Regulatory effects of IFN‐β on production of osteopontin and IL‐17 by CD4+ T Cells in MS

IFN‐β currently serves as one of the major treatments for MS. Its anti‐inflammatory mechanism has been reported as involving a shift in cytokine balance from Th1 to Th2 in the T‐cell response against elements of the myelin sheath. In addition to the Th1 and Th2 groups, two other important pro‐inflammatory cytokines, IL‐17 and osteopontin (OPN), are believed to play important roles in CNS inflammation in the pathogenesis of MS. In this study, we examined the potential effects of IFN‐β on the regulation of OPN and IL‐17 in MS patients. We found that IFN‐β used in vitro at 0.5–3 ng/mL significantly inhibited the production of OPN in primary T cells derived from PBMC. The inhibition of OPN was determined to occur at the CD4⁺ T‐cell level. In addition, IFN‐β inhibited the production of IL‐17 and IL‐21 in CD4⁺ T cells. It has been described that IFN‐β suppresses IL‐17 production through the inhibition of a monocytic cytokine, the intracellular translational isoform of OPN. Our further investigation demonstrated that IFN‐β also acted directly on the CD4⁺ T cells to regulate OPN and IL‐17 expression through the type I IFN receptor‐mediated activation of STAT1 and suppression of STAT3 activity. Administration of IFN‐β to EAE mice ameliorated the disease severity. Furthermore, spinal cord infiltration of OPN⁺ and IL‐17⁺ cells decreased in IFN‐β‐treated EAE mice along with decreases in serum levels of OPN and IL‐21. Importantly, decreased OPN production by IFN‐β treatment contributes to the reduced migratory activity of T cells. Taken together, the results from both in vitro and in vivo experiments indicate that IFN‐β treatment can down‐regulate the OPN and IL‐17 production in MS. This study provides new insights into the mechanism of action of IFN‐β in the treatment of MS.     

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.     

Crosstalk between human DC subsets promotes antibacterial activity and CD8+ T‐cell stimulation in response to bacille Calmette‐Guérin

To date, little is known about the unique contributions of specialized human DC subsets to protection against tuberculosis (TB). Here, we focus on the role of human plasmacytoid (p)DCs and myeloid (m)DCs in the immune response to the TB vaccine bacille Calmette‐Guérin (BCG). Ex vivo DC subsets from human peripheral blood were purified and infected with BCG expressing GFP to distinguish between infected and noninfected cells. BDCA‐1⁺ myeloid DCs were more susceptible than BDCA‐3⁺ mDCs to BCG infection. Plasmacytoid DCs have poor phagocytic activity but are equipped with endocytic receptors and can be activated by bystander stimulation. Consequently, the mutual interaction of the two DC subsets in response to BCG was analyzed. We found that pDCs were activated by BCG‐infected BDCA‐1⁺ mDCs to upregulate maturation markers and to produce granzyme B, but not IFN‐α. Reciprocally, the presence of activated pDCs enhanced mycobacterial growth control by infected mDCs and increased IL‐1β availability. The synergy between the two DC subsets promoted BCG‐specific CD8⁺ T‐cell stimulation and the role of BCG‐infected BDCA‐1⁺ mDCs could not be efficiently replaced by infected BDCA‐3⁺ mDCs in the crosstalk with pDCs. We conclude that mDC–pDC crosstalk should be exploited for rational design of next‐generation TB vaccines.     

The siRNA cocktail targeting interleukin 10 receptor and transforming growth factor‐β receptor on dendritic cells potentiates tumour antigen‐specific CD8+ T cell immunity

Dendritic cells (DCs) are promising therapeutic agents in the field of cancer immunotherapy due to their intrinsic immune‐priming capacity. The potency of DCs, however, is readily attenuated immediately after their administration in patients as tumours and various immune cells, including DCs, produce various immunosuppressive factors such as interleukin (IL)‐10 and transforming growth factor (TGF)‐β that hamper the function of DCs. In this study, we used small interfering RNA (siRNA) to silence the expression of endogenous molecules in DCs, which can sense immunosuppressive factors. Among the siRNAs targeting various immunosuppressive molecules, we observed that DCs transfected with siRNA targeting IL‐10 receptor alpha (siIL‐10RA) initiated the strongest antigen‐specific CD8⁺ T cell immune responses. The potency of siIL‐10RA was enhanced further by combining it with siRNA targeting TGF‐β receptor (siTGF‐βR), which was the next best option during the screening of this study, or the previously selected immunoadjuvant siRNA targeting phosphatase and tensin homologue deleted on chromosome 10 (PTEN) or Bcl‐2‐like protein 11 (BIM). In the midst of sorting out the siRNA cocktails, the cocktail of siIL‐10RA and siTGF‐βR generated the strongest antigen‐specific CD8⁺ T cell immunity. Concordantly, the knock‐down of both IL‐10RA and TGF‐βR in DCs induced the strongest anti‐tumour effects in the TC‐1 P0 tumour model, a cervical cancer model expressing the human papillomavirus (HPV)‐16 E7 antigen, and even in the immune‐resistant TC‐1 (P3) tumour model that secretes more IL‐10 and TGF‐β than the parental tumour cells (TC‐1 P0). These results provide the groundwork for future clinical development of the siRNA cocktail‐mediated strategy by co‐targeting immunosuppressive molecules to enhance the potency of DC‐based vaccines.     

Cytokine‐dependent regulation of dendritic cell differentiation in the splenic microenvironment

The DC‐derived chemokine CCL17, a ligand of CCR4, has been shown to promote various inflammatory diseases such as atopic dermatitis, atherosclerosis, and inflammatory bowel disease. Under steady‐state conditions, and even after systemic stimulation with LPS, CCL17 is not expressed in resident splenic DCs as opposed to CD8α^?CD11b⁺ LN DCs, which produce large amounts of CCL17 in particular after maturation. Upon systemic NKT cell activation through α‐galactosylceramide stimulation however, CCL17 can be upregulated in both CD8α^? and CD8α⁺ splenic DC subsets and enhances cross‐presentation of exogenous antigens. Based on genome‐wide expression profiling, we now show that splenic CD11b⁺ DCs are susceptible to IFN‐γ‐mediated suppression of CCL17, whereas LN CD11b⁺CCL17⁺ DCs downregulate the IFN‐γR and are much less responsive to IFN‐γ. Under inflammatory conditions, particularly in the absence of IFN‐γ signaling in IFN‐γRKO mice, CCL17 expression is strongly induced in a major proportion of splenic DCs by the action of GM‐CSF in concert with IL‐4. Our findings demonstrate that the local cytokine milieu and differential cytokine responsiveness of DC subsets regulate lymphoid organ specific immune responses at the level of chemokine expression.     

Immature dendritic cells convert anergic nonregulatory T cells into Foxp3−IL‐10+ regulatory T cells by engaging CD28 and CTLA‐4

Anergic T cells can survive for long time periods passively in a hyporesponsive state without obvious active functions. Thus, the immunological reason for their maintenance is unclear. Here, we induced peptide‐specific anergy in T cells from mice by coculturing these cells with immature murine dendritic cells (DCs). We found that these anergic, nonsuppressive IL‐10^?Foxp3^?CTLA‐4⁺CD25^lowEgr2⁺ T cells could be converted into suppressive IL‐10⁺Foxp3^?CTLA‐4⁺CD25^highEgr2⁺ cells resembling type‐1 Treg cells (Tr1) when stimulated a second time by immature DCs in vitro. Addition of TGF‐β during anergy induction favored Foxp3⁺ Treg‐cell induction, while TGF‐β had little effect when added to the second stimulation. Expression of both CD28 and CTLA‐4 molecules on anergic T cells was required to allow their conversion into Tr1‐like cells. Suppressor activity was enabled via CD28‐mediated CD25 upregulation, acting as an IL‐2 sink, together with a CTLA‐4‐mediated inhibition of NFATc1/α activation to shut down IL‐2‐mediated proliferation. Together, these data provide evidence and mechanistical insights into how persistent anergic T cells may serve as a resting memory pool for Tr1‐like cells.     

Curcumin induces the tolerogenic dendritic cell that promotes differentiation of intestine‐protective regulatory T cells

The gut is home to a large number of Treg, with both CD4⁺ CD25⁺ Treg and bacterial antigen‐specific Tr1 cells present in normal mouse intestinal lamina propria. It has been shown recently that intestinal mucosal DC are able to induce Foxp3⁺ Treg through production of TGF‐β plus retinoic acid (RA). However, the factors instructing DC toward this mucosal phenotype are currently unknown. Curcumin has been shown to possess a number of biologic activities including the inhibition of NF‐κB signaling. We asked whether curcumin could modulate DC to be tolerogenic whose function could mimic mucosal DC. We report here that curcumin modulated BM‐derived DC to express ALDH1a and IL‐10. These curcumin‐treated DC induced differentiation of naïve CD4⁺ T cells into Treg resembling Treg in the intestine, including both CD4⁺CD25⁺ Foxp3⁺ Treg and IL‐10‐producing Tr1 cells. Such Treg induction required IL‐10, TGF‐β and retinoic acid produced by curcumin‐modulated DC. Cell contact as well as IL‐10 and TGF‐β production were involved in the function of such induced Treg. More importantly, these Treg inhibited antigen‐specific T‐cell activation in vitro and inhibited colitis due to antigen‐specific pathogenic T cells in vivo.     

TGF‐β induces the differentiation of human CXCL13‐producing CD4+ T cells

In the ectopic lymphoid‐like structures present in chronic inflammatory conditions such as rheumatoid arthritis, a subset of human effector memory CD4⁺ T cells that lacks features of follicular helper T (Tfh) cells produces CXCL13. Here, we report that TGF‐β induces the differentiation of human CXCL13‐producing CD4⁺ T cells from naïve CD4⁺ T cells. The TGF‐β‐induced CXCL13‐producing CD4⁺ T cells do not express CXCR5, B‐cell lymphoma 6 (BCL6), and other Tfh‐cell markers. Furthermore, expression levels of CD25 (IL‐2Rα) in CXCL13‐producing CD4⁺ T cells are significantly lower than those in FoxP3⁺ in vitro induced Treg cells. Consistent with this, neutralization of IL‐2 and knockdown of STAT5 clearly upregulate CXCL13 production by CD4⁺ T cells, while downregulating the expression of FoxP3. Furthermore, overexpression of FoxP3 in naïve CD4⁺ T cells downregulates CXCL13 production, and knockdown of FoxP3 fails to inhibit the differentiation of CXCL13‐producing CD4⁺ T cells. As reported in rheumatoid arthritis, proinflammatory cytokines enhance secondary CXCL13 production from reactivated CXCL13‐producing CD4⁺ T cells. Our findings demonstrate that CXCL13‐producing CD4⁺ T cells lacking Tfh‐cell features differentiate via TGF‐β signaling but not via FoxP3, and exert their function in IL‐2‐limited but TGF‐β‐rich and proinflammatory cytokine‐rich inflammatory conditions.     

TGF‐β interactions with IL‐1 family members trigger IL‐4‐independent IL‐9 production by mouse CD4+ T cells

TGF‐β and IL‐4 were recently shown to selectively upregulate IL‐9 production by naïve CD4⁺ T cells. We report here that TGF‐β interactions with IL‐1α, IL‐1β, IL‐18, and IL‐33 have equivalent IL‐9‐stimulating activities that function even in IL‐4‐deficient animals. This was observed after in vitro antigenic stimulation of immunized or unprimed mice and after polyclonal T‐cell activation. Based on intracellular IL‐9 staining, all IL‐9‐producing cells were CD4⁺ and 80–90% had proliferated, as indicated by reduced CFSE staining. In contrast to IL‐9, IL‐13 and IL‐17 were strongly stimulated by IL‐1 and either inhibited (IL‐13) or were unaffected (IL‐17) by addition of TGF‐β. IL‐9 and IL‐17 production also differed in their dependence on IL‐2 and regulation by IL‐1/IL‐23. As IL‐9 levels were much lower in Th2 and Th17 cultures, our results identify TGF‐β/IL‐1 and TGF‐β/IL‐4 as the main control points of IL‐9 synthesis.     

Generation of highly effective and stable murine alloreactive Treg cells by combined anti‐CD4 mAb,TGF‐β, and RA treatment

The transfer of alloreactive regulatory T (aTreg) cells into transplant recipients represents an attractive treatment option to improve long‐term graft acceptance. We recently described a protocol for the generation of aTreg cells in mice using a nondepleting anti‐CD4 antibody (aCD4). Here, we investigated whether adding TGF‐β and retinoic acid (RA) or rapamycin (Rapa) can further improve aTreg‐cell generation and function. Murine CD4⁺ T cells were cultured with allogeneic B cells in the presence of aCD4 alone, aCD4+TGF‐β+RA or aCD4+Rapa. Addition of TGF‐β+RA or Rapa resulted in an increase of CD25⁺Foxp3⁺‐expressing T cells. Expression of CD40L and production of IFN‐γ and IL‐17 was abolished in aCD4+TGF‐β+RA aTreg cells. Additionally, aCD4+TGF‐β+RA aTreg cells showed the highest level of Helios and Neuropilin‐1 co‐expression. Although CD25⁺Foxp3⁺ cells from all culture conditions displayed complete demethylation of the Treg‐specific demethylated region, aCD4+TGF‐β+RA Treg cells showed the most stable Foxp3 expression upon restimulation. Consequently, aCD4+TGF‐β+RA aTreg cells suppressed effector T‐cell differentiation more effectively in comparison to aTreg cells harvested from all other cultures, and furthermore inhibited acute graft versus host disease and especially skin transplant rejection. Thus, addition of TGF‐β+RA seems to be superior over Rapa in stabilising the phenotype and functional capacity of aTreg cells.     

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.     

Direct effect of dsRNA mimetics on cancer cells induces endogenous IFN‐β production capable of improving dendritic cell function

Viral double‐stranded RNA (dsRNA) mimetics have been explored in cancer immunotherapy to promote antitumoral immune response. Polyinosine–polycytidylic acid (poly I:C) and polyadenylic–polyuridylic acid (poly A:U) are synthetic analogs of viral dsRNA and strong inducers of type I interferon (IFN). We describe here a novel effect of dsRNA analogs on cancer cells: besides their potential to induce cancer cell apoptosis through an IFN‐β autocrine loop, dsRNA‐elicited IFN‐β production improves dendritic cell (DC) functionality. Human A549 lung and DU145 prostate carcinoma cells significantly responded to poly I:C stimulation, producing IFN‐β at levels that were capable of activating STAT1 and enhancing CXCL10, CD40, and CD86 expression on human monocyte‐derived DCs. IFN‐β produced by poly I:C‐activated human cancer cells increased the capacity of monocyte‐derived DCs to stimulate IFN‐γ production in an allogeneic stimulatory culture in vitro. When melanoma murine B16 cells were stimulated in vitro with poly A:U and then inoculated into TLR3^?/? mice, smaller tumors were elicited. This tumor growth inhibition was abrogated in IFNAR1^?/? mice. Thus, dsRNA compounds are effective adjuvants not only because they activate DCs and promote strong adaptive immunity, but also because they can directly act on cancer cells to induce endogenous IFN‐β production and contribute to the antitumoral response.     

Attenuated TGF‐β1 responsiveness of dendritic cells and their precursors in atopic dermatitis

The responsiveness of DCs and their precursors to transforming growth factor beta1 (TGF‐β1) affects the nature of differentiating DC subsets, which are essential for the severity of atopic dermatitis (AD). To evaluate TGF‐β signaling in monocytes and monocyte‐derived DCs of AD patients compared with that of controls, in vitro generated Langerhans cell (LC) like DCs, expression of TGF‐β receptors, phospho‐Smad2/3 and Smad7 were evaluated. Furthermore, TNF‐α expression and synergistic effects of TNF‐α upon TGF‐β signaling and DC generation were evaluated. We found LC‐like DC differentiation of monocytes from AD patients in response to TGF‐β1 was remarkably reduced and TGF‐β1 receptor expression was significantly lower compared with that of healthy controls. Attenuated TGF‐β1 responsiveness mirrored by lower phospho‐Smad2/3 expression after TGF‐β1 stimulation and higher expression of inhibitory Smad7 was observed in monocytes from AD patients. During DC generation, mRNA expression of Smad7 was relatively higher in LC‐like DCs of AD patients. Lower TNF‐α expression of monocytes from AD patients might further contribute to attenuated TGF‐β signaling in the disease since TNF‐α had synergistic effects on TGF‐β1 signaling and LC generation through mediating the degradation of Smad7. Our results demonstrate alleviated TGF‐β1 signaling together with the amount of soluble co‐factors might direct the nature of differentiating DCs.