Human Myeloid Dendritic Cells Research Articles

Human Myeloid Dendritic Cells (mDCs) exposed to Interleukin-4 (IL-4) secrete CCL17 and recruit Memory T lymphocytes

Human Myeloid Dendritic Cells (mDCs) exposed to Interleukin-4 (IL-4) secrete CCL17 and recruit Memory T lymphocytes

Wasabi Component 6-(Methylsulfinyl)hexly Isothiocyanate and Derivatives Improve the Survival of Skin Allografts.

We tested the effect of 6-(Methylsulfinyl)hexyl Isothiocyanate (6-MITC) and derivatives (I7447 and I7557) on the differentiation and maturation of human myeloid dendritic cells (DCs) in vitro, and skin transplantation in vivo. Triggering of CD14+ myeloid monocyte development toward myeloid DCs with and without 6-MITC and derivatives to examine the morphology, viability, surface marker expression, and cytokine production. Stimulatory activity on allogeneic naive T cells was measured by proliferation and interferon-γ production. The skin allograft survival area model was used to translate the 6-MITC and derivatives’ antirejection effect. All of the compounds had no significant effects on DC viability and reduced the formation of dendrites at concentrations higher than 10 μM. At this concentration, 6-MITC and I7557, but not I7447, inhibited the expression of CD1a and CD83. Both 6-MITC and I7557 exhibited T-cells and interferon-γ augmentation at lower concentrations and suppression at higher concentration. The 6-MITC and I7557 prolonged skin graft survival. Both the 6-MITC and I7557 treatment resulted in the accumulation of regulatory T cells in recipient rat spleens. No toxicity was evident in 6-MITC and I7557 treatment. The 6-MITC and I7557 induced human DC differentiation toward a tolerogenic phenotype and prolonged rat skin allograft survival. These compounds may be effective as immunosuppressants against transplant rejection.

Peanut protein acts as a TH2 adjuvant by inducing RALDH2 in human antigen-presenting cells

Peanut is a potent inducer of proallergenic TH2 responses in susceptible individuals. Antigen-presenting cells (APCs) including dendritic cells and monocytes instruct naive Tcells to differentiate into various effector cells, determining immune responses such as allergy and tolerance. We sought to detect peanut protein (PN)-induced changes in gene expression in human myeloid dendritic cells (mDCs) and monocytes, identify signaling receptors that mediate these changes, and assess how PN-induced genes in mDCs impact their ability to promote T-cell differentiation. mDCs, monocytes, and naive CD4+ T cells were isolated from blood bank donors and peanut-allergic patients. APCs were incubated with PN and other stimulants, and gene expression was measured using microarray and RT quantitative PCR. To assess T-cell differentiation, mDCs were cocultured with naive TH cells. PN induced a unique gene expression profile in mDCs, including the gene that encodes retinaldehyde dehydrogenase 2 (RALDH2), a rate-limiting enzyme in the retinoic acid (RA)-producing pathway. Stimulation of mDCs with PN also induced a 7-fold increase in the enzymatic activity of RALDH2. Blocking antibodies against Toll-like receptor (TLR)1/TLR2, as well as small interfering RNA targeting TLR1/TLR2, reduced the expression of RALDH2 in PN-stimulated APCs by 70%. Naive TH cells cocultured with PN-stimulated mDCs showed an RA-dependent 4-fold increase in production of IL-5 and expression of integrin α4β7. PN induces RALDH2 in human APCs by signaling through the TLR1/TLR2 heterodimer. This leads to production of RA, which acts on TH cells to induce IL-5 and gut-homing integrin. RALDH2 induction by PN in APCs and RA-promoted TH2 differentiation could be an important factor determining allergic responses to peanut.

Phosphate-modif ied CpG oligonucleotides induce in vitro maturation of human myeloid dendritic cells.

Myeloid dendritic cells (DCs) play an important role in the immune response; therefore, the search for compounds that can effectively activate DCs is a needful goal. This study was aimed to investigate the effect of synthetic CpG oligodeoxynucleotides (CpG-ODN) on the maturation and allostimulatory activity of myeloid DCs in comparison with other PAMP and DAMP molecules. For the research, we synthesized known CpG-ODN class C (SD-101 and D-SL03) containing thiophosphate internucleotide groups, and their original phosphate-modified analogues (SD-101M and D- SL03M) with mesylphosphoramide internucleotide groups (M = μ-modification). The effects of CpG-ODN and other activators were evaluated on DCs generated from blood monocytes in the presence of GM-CSF and IFN-α (IFN-DC) or IL-4 (IL4-DC). Evaluation of the intracellular TLR-9 expression showed that both types of DCs (IFN-DC and IL4-DC) contained on average 52 and 80 % of TLR-9-positive cells, respectively. The CpG-ODNs studied enhanced the allostimulatory activity of IFN-DCs, and the effect of μ-modified CpG-ODNs was higher than that of CpG-ODNs with thiophosphate groups. The stimulating effect of CpG-ODN at a dose of 1.0 μg/ml was comparable (for D-SL03, D-SL03M, SD-101) with or exceeded (for SD-101M) the effect of LPS at a dose of 10 μg/ml. At the same time, IFN-DCs were characterized by greater sensitivity to the action of CpG-ODNs than IL4-DCs. The enhancement of DC allostimulatory activity in the presence of CpG-ODNs was associated with the induction of final DC maturation, which was confirmed by a significant decrease in the number of CD14+DC, an increase in mature CD83+DC and a trend towards an increase in CD86+DC. Interestingly, the characteristic ability of LPS to enhance the expression of the co-stimulatory molecule OX40L on DCs was revealed only for the μ-analogue SD-101M. In addition, CpG-ODNs (SD-101 and SD-101M) had a stimulatory effect on IFN-γ production comparable to the action of LPS. The data obtained indicate a stimulating effect of CpG-ODN on the maturation and allostimulatory activity of human myeloid DCs, which is more pronounced for μ-modified analogs.

A MALT1 inhibitor suppresses human myeloid DC, effector T-cell and B-cell responses and retains Th1/regulatory T-cell homeostasis.

The paracaspase mucosa-associated lymphoid tissue lymphoma translocation protein-1 (MALT1) regulates nuclear-factor-kappa-B (NF-κB) activation downstream of surface receptors with immunoreceptor tyrosine-based activation motifs (ITAMs), such as the B-cell or T-cell receptor and has thus emerged as a therapeutic target for autoimmune diseases. However, recent reports demonstrate the development of lethal autoimmune inflammation due to the excessive production of interferon gamma (IFN-ɣ) and defective differentiation of regulatory T-cells in genetically modified mice deficient in MALT1 paracaspase activity. To address this issue, we explored the effects of pharmacological MALT1 inhibition on the balance between T-effector and regulatory T-cells. Here we demonstrate that allosteric inhibition of MALT1 suppressed Th1, Th17 and Th1/Th17 effector responses, and inhibited T-cell dependent B-cell proliferation and antibody production. Allosteric MALT1 inhibition did not interfere with the suppressive function of human T-regulatory cells, although it impaired de novo differentiation of regulatory T-cells from naïve T-cells. Treatment with an allosteric MALT1 inhibitor alleviated the cytokine storm, including IFN-ɣ, in a mouse model of acute T-cell activation, and long-term treatment did not lead to an increase in IFN-ɣ producing CD4 cells or tissue inflammation. Together, our data demonstrate that the effects of allosteric inhibition of MALT1 differ from those seen in mice with proteolytically inactive MALT1, and thus we believe that MALT1 is a viable target for B and T-cell driven autoimmune diseases.

Immunomodulatory drugs suppress Th1-inducing ability of dendritic cells but enhance Th2-mediated allergic responses

AbstractImmunomodulatory drugs (IMiDs), lenalidomide and pomalidomide, are widely used treatments for multiple myeloma; however, they occasionally lead to episodes of itchy skin and rashes. Here, we analyzed the effects of IMiDs on human myeloid dendritic cells (mDCs) as major regulators of Th1 or Th2 responses and the role they play in allergy. We found that lenalidomide and pomalidomide used at clinical concentrations did not affect the survival or CD86 and OX40-ligand expression of blood mDCs in response to lipopolysaccharide (LPS) and thymic stromal lymphopoietin (TSLP) stimulation. Both lenalidomide and pomalidomide dose-dependently inhibited interleukin-12 (IL-12) and TNF production and STAT4 expression, and enhanced IL-10 production in response to LPS. When stimulated with TSLP, both IMiDs significantly enhanced CCL17 production and STAT6 and IRF4 expression and promoted memory Th2-cell responses. In 46 myeloma patients, serum CCL17 levels at the onset of lenalidomide-associated rash were significantly higher than those without rashes during lenalidomide treatment and those before treatment. Furthermore, serum CCL17 levels in patients who achieved a very good partial response (VGPR) were significantly higher compared with a less than VGPR during lenalidomide treatment. The median time to next treatment was significantly longer in lenalidomide-treated patients with rashes than those without. Collectively, IMiDs suppressed the Th1-inducing capacity of DCs, instead promoting a Th2 response. Thus, the lenalidomide-associated rashes might be a result of an allergic response driven by Th2-axis activation. Our findings suggest clinical efficacy and rashes as a side effect of IMiDs are inextricably linked through immunostimulation.

Lack of Activation Marker Induction and Chemokine Receptor Switch in Human Neonatal Myeloid Dendritic Cells in Response to Human Respiratory Syncytial Virus.

Respiratory syncytial virus (RSV) infects and causes disease in infants and reinfects with reduced disease throughout life without significant antigenic change. In contrast, reinfection by influenza A virus (IAV) largely requires antigenic change. The adaptive immune response depends on antigen presentation by dendritic cells (DC), which may be too immature in young infants to induce a fully protective immune response against RSV reinfections. We therefore compared the ability of RSV and IAV to activate primary human cord blood (CB) and adult blood (AB) myeloid DC (mDC). While RSV and IAV infected with similar efficiencies, RSV poorly induced maturation and cytokine production in CB and AB mDC. This difference between RSV and IAV was more profound in CB mDC. While IAV activated CB mDC to some extent, RSV did not induce CB mDC to increase the maturation markers CD38 and CD86 or CCR7, which directs DC migration to lymphatic tissue. Low CCR7 surface expression was associated with high expression of CCR5, which keeps DC in inflamed peripheral tissues. To evaluate a possible inhibition by RSV, we subjected RSV-inoculated AB mDC to secondary IAV inoculation. While RSV-inoculated AB mDC responded to secondary IAV inoculation by efficiently upregulating activation markers and cytokine production, IAV-induced CCR5 downregulation was slightly inhibited in cells exhibiting robust RSV infection. Thus, suboptimal stimulation and weak and mostly reversible inhibition seem to be responsible for inefficient mDC activation by RSV. The inefficient mDC stimulation and immunological immaturity in young infants may contribute to reduced immune responses and incomplete protection against RSV reinfection.IMPORTANCE Respiratory syncytial virus (RSV) causes disease early in life and can reinfect symptomatically throughout life without undergoing significant antigenic change. In contrast, reinfection by influenza A virus (IAV) requires antigenic change. The adaptive immune response depends on antigen presentation by dendritic cells (DC). We used myeloid DC (mDC) from cord blood and adult blood donors to evaluate whether immunological immaturity contributes to the inability to mount a fully protective immune response to RSV. While IAV induced some activation and chemokine receptor switching in cord blood mDC, RSV did not. This appeared to be due to a lack of activation and a weak and mostly reversible inhibition of DC functions. Both viruses induced a stronger activation of mDC from adults than mDC from cord blood. Thus, inefficient stimulation of mDC by RSV and immunological immaturity may contribute to reduced immune responses and increased susceptibility to RSV disease and reinfection in young infants.

Concomitant Targeting of FLT3 and BTK with CG'806 Overcomes FLT3-Inhibitor Resistance through Inhibition of Autophagy

Fms-like tyrosine kinase 3 (FLT3)-targeted therapy represents an important paradigm in the management of patients with highly aggressive FLT3 mutated acute myeloid leukemia (AML). However, clinical efficacy is usually transient and followed by emergence of resistance to FLT3-inhibitors (Borthakur et al., 2011; Cortes et al., 2013; Zhang et al., 2008). Such resistance often results from acquired mutations of TKD, which are frequently identified in D835, Y842 and F691 residues (Smith et al., 2015; Smith et al., 2012; Zhang et al., 2014). It was reported that the FLT3-ITD-targeting drug sorafenib can induce autophagy in human myeloid dendritic cells (Lin et al., 2013). Induction of autophagy has also been reported to play a crucial role in resistance to BCR-ABL targeted imatinib therapy in CML (Hekmatshoar et al., 2018). Additionally, inhibition of autophagy can re-sensitize cancer cells to apoptosis induction (Fitzwalter et al., 2018; Piya et al., 2017), suggesting that inhibition of autophagy may represent a novel therapeutic strategy for overcoming resistance to FLT3-targeted therapy.In the present study, we assessed autophagy levels in leukemia cell lines bearing different FLT3 mutations and in AML patient samples obtained from sorafenib-resistant patients. All tested resistant cell lines bearing TKD or ITD+TKD mutations showed increased basal autophagy levels. Resistant AML patient samples also demonstrated greater autophagy compared to matched pre-treatment samples in FLT3-mutated, but not in FLT3-wild type samples. Upregulation of autophagy was also observed in the bone marrow (BM)-mimetic microenvironment (i.e., hypoxia and the presence of mesenchymal stem cells (MSCs) in vitro. Inhibition of autophagy with chloroquine (CQ) potentiated quizartinib-induced apoptosis and partially abrogated MSC-mediated protection in FLT3-ITD- and/or D835-mutated AML cells by suppressing c-Myc, mTOR/S6K signaling and activating transcription factor 4 (ATF4).We also observed upregulation of BTK activation accompanied by increased autophagy levels in hypoxic/MSC co-culture with leukemic cells and in resistant primary patient samples. Co-targeting BTK and FLT3 with ibrutinib (or BTK siRNA) and quizartinib enhanced leukemic cell killing and abrogates MSC-mediated protection of FLT3 mutated leukemia cells. We further investigated a novel, highly potent small molecule pan-FLT3/pan-BTK kinase inhibitor CG-806 (IC50s 0.8 and 5.0 nM against FLT3-ITD and BTK, respectively) (Aptose, San Diego, CA). CG'806 abolished MSC/hypoxia-mediated protection of AML cells and induced apoptosis in FLT3-mutated cells in vitro. Of note, CG'806, but not quizartinib, exerted profound pro-apoptotic effects in primary AML patient cells harboring ITD+D835 mutations ex vivo. Further evaluation in a PDX leukemia model inoculated with the ITD+D835 mutated primary AML cells showed that CG'806 significantly reduced leukemia cell burden and benefited for mouse survival.Taken together, autophagy is associated with AML resistance to FLT3-targeted therapy, which can be overcome by the pan-FLT3/pan-BTK kinase inhibitor CG-806 through concomitant blockade of FLT3 and BTK. Co-targeting FLT3 and BTK might provide a strategy for preventing/overcoming FLT3 inhibitor resistance in AML patients with FLT3 mutations. Phase I trials of CG'806 are in preparation. DisclosuresZhang:Aptose Biosciences, Inc: Employment. Battula:United Therapeutics Inc.: Patents & Royalties, Research Funding. Konopleva:Stemline Therapeutics: Research Funding. Rice:Aptose Biosciences, Inc: Equity Ownership. Andreeff:Eutropics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Reata: Equity Ownership; SentiBio: Equity Ownership; Oncolyze: Equity Ownership; Astra Zeneca: Research Funding; Jazz Pharma: Consultancy; Oncoceutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; United Therapeutics: Patents & Royalties: GD2 inhibition in breast cancer ; Aptose: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy, Patents & Royalties: MDM2 inhibitor activity patent, Research Funding; Amgen: Consultancy, Research Funding; Celgene: Consultancy.

Myeloma Cells Have the Ability to Suppress Th1-Inducing Capacity but Enhance Th2-Mediated Response of Dendritic Cells By Producing Factors Other Than Soluble SLAMF7

Background: Lenalidomide (LEN), as a backbone drug for multiple myeloma (MM), has both direct tumoricidal and immunomodulatory effects in MM. LEN displays immunopotentiating activity, including augmentation of T and natural killer cell function and to induce selective reduction of regulatory T cells. Thus, the immune-based cancer treatments are currently important in MM therapy. Since myeloma cells together with immune cells are immersed in the pathogenic micro-environment, understanding the influence of micro-environment against myeloma cells and immune system may lead to the development of novel treatment strategies for MM. Series of analyses have clarified a functional plasticity of dendritic cells (DCs) to induce Th1 or Th2 response and DCs are pivotal in orchestrating both innate and acquire immune responses also in the anti-tumor immunity. Here, we focused on the effects of myeloma environment to modulate the human myeloid DCs (mDCs), which are the major regulators to induce Th1 or Th2 responses. Soluble form of SLAMF7 (sSLAMF7) is a pivotal environmental component of MM and functions as a self-ligand of myeloma cells. sSLAMF7 has been detected in the serum of patients with MM at higher levels than healthy individuals and therefore may presumably play some roles in pathophysiological condition of MM. To evaluate the functions of soluble factors/components derived from myeloma cells, we analyzed whether supernatants of myeloma cell lines could modulate mDC functions. Methods: Using cell sorting, blood human CD11+ mDCs were isolated from healthy adult volunteers. The DC functions were analyzed after culture for 24 h with supernatant of myeloma cell lines, NCI-H929 (H929) or MM.1R. This study was approved by the Institutional Review Board of Kansai Medical University.Results: We here found that both supernatants of myeloma cell lines, H929 and MM.1R did not affect CD86 expression on mDCs in response to toll-like receptor (TLR)-ligand (R848), but upregulated their CD86 expression in response to Th2-inducing cytokine, thymic stromal lymphopoietin (TSLP). Of note, the supernatants inhibited mDC-derived IL-12 production in response to R848 (p < 0.05: H929; 25-30% of cont. and MM1.R; less than 50 % of cont.), while in response to TSLP, dose-dependently enhanced the Th2-recruiting chemokine CCL17/TARC production (p < 0.05: H929; 130- 210 % of cont. and MM1.R; 120-185 % of cont.), which functions as chemoattractant for memory Th2 cells and contribute to promote humoral response. In addition, we revealed that these capacities were further enhanced by the addition of LEN at clinical in vivo plasma concentration of 1 µM. Thus, MM micro-environment could have the potential to shift DC-mediated response from Th1 to Th2. To clarify whether sSLAMF7 in the supernatant of myeloma cell lines play a role in the Th1/Th2-modulating effect, we calculated the sSLAMF7 concentration in the supernatants and analyzed an inhibitory effect of elotuzumab for the DC function induced by the supernatants. sSLAMF7 could not be detected at all in the supernatants of both myeloma cell lines, even in any concentration of cells. Furthermore, addition of 30 to 100 ug/ml (clinical trough serum concentration) elotuzumab into the culture of mDCs and the supernatants did not affect the CD86 expression and IL-12/CCL17 production. Hence, factors other than sSLAMF7 from myeloma cells can trigger DCs to suppress Th1 response and to promote Th2 response.Conclusion: Our data suggest that the MM micro-environment, while suppress the Th1-inducing capacity, rather lead to enhance Th2 response at DC phase. As sSLAMF7 is detected in the serum of patients with MM but not in the supernatants of MM cell lines in the experimental setting, there is a limitation that our data does not consider the action of sSLAMF7. However, the present result provides an important clue for understanding the biological basis for the MM micro-environment against host immune defense at onset. DisclosuresIto:Bristol-Myers Squibb: Honoraria, Research Funding; Takeda: Honoraria; Novartis Pharma: Honoraria; Pfizer: Honoraria; Mundipharma: Honoraria; Celgene: Honoraria.

Human Bone Marrow-Derived Myeloid Dendritic Cells Show an Immature Transcriptional and Functional Profile Compared to Their Peripheral Blood Counterparts and Separate from Slan+ Non-Classical Monocytes.

The human bone marrow (BM) gives rise to all distinct blood cell lineages, including CD1c+ (cDC2) and CD141+ (cDC1) myeloid dendritic cells (DC) and monocytes. These cell subsets are also present in peripheral blood (PB) and lymphoid tissues. However, the difference between the BM and PB compartment in terms of differentiation state and immunological role of DC is not yet known. The BM may represent both a site for development as well as a possible effector site and so far, little is known in this light with respect to different DC subsets. Using genome-wide transcriptional profiling we found clear differences between the BM and PB compartment and a location-dependent clustering for cDC2 and cDC1 was demonstrated. DC subsets from BM clustered together and separate from the corresponding subsets from PB, which similarly formed a cluster. In BM, a common proliferating and immature differentiating state was observed for the two DC subsets, whereas DC from the PB showed a more immune-activated mature profile. In contrast, BM-derived slan+ non-classical monocytes were closely related to their PB counterparts and not to DC subsets, implying a homogenous prolife irrespective of anatomical localization. Additional functional tests confirmed these transcriptional findings. DC-like functions were prominently exhibited by PB DC. They surpassed BM DC in maturation capacity, cytokine production, and induction of CD4+ and CD8+ T cell proliferation. This first study on myeloid DC in healthy human BM offers new information on steady state DC biology and could potentially serve as a starting point for further research on these immune cells in healthy conditions as well as in diseases.

Naturally produced type I IFNs enhance human myeloid dendritic cell maturation and IL-12p70 production and mediate elevated effector functions in innate and adaptive immune cells

There has recently been a paradigm shift in the field of dendritic cell (DC)-based immunotherapy, where several clinical studies have confirmed the feasibility and advantageousness of using directly isolated human blood-derived DCs over in vitro differentiated subsets. There are two major DC subsets found in blood; plasmacytoid DCs (pDCs) and myeloid DCs (mDCs), and both have been tested clinically. CD1c+ mDCs are highly efficient antigen-presenting cells that have the ability to secrete IL-12p70, while pDCs are professional IFN-α-secreting cells that are shown to induce innate immune responses in melanoma patients. Hence, combining mDCs and pDCs poses as an attractive, multi-functional vaccine approach. However, type I IFNs have been reported to inhibit IL-12p70 production and mDC-induced T-cell activation. In this study, we investigate the effect of IFN-α on mDC maturation and function. We demonstrate that both recombinant IFN-α and activated pDCs strongly enhance mDC maturation and increase IL-12p70 production. Co-cultured mDCs and pDCs additionally have beneficial effect on NK and NKT-cell activation and also enhances IFN-γ production by allogeneic T cells. In contrast, the presence of type I IFNs reduces the proliferative T-cell response. The mere presence of a small fraction of activated pDCs is sufficient for these effects and the required ratio between the subsets is non-stringent. Taken together, these results support the usage of mDCs and pDCs combined into one immunotherapeutic vaccine with broad immunostimulatory features.

TRIM29 Negatively Regulates the Type I IFN Production in Response to RNA Virus.

The innate immunity is critically important in protection against virus infections, and in the case of RNA viral infections, the signaling mechanisms that initiate robust protective innate immunity without triggering autoimmune inflammation remain incompletely defined. In this study, we found the E3 ligase TRIM29 was specifically expressed in poly I:C-stimulated human myeloid dendritic cells. The induced TRIM29 played a negative role in type I IFN production in response to poly I:C or dsRNA virus reovirus infection. Importantly, the challenge of wild-type mice with reovirus led to lethal infection. In contrast, deletion of TRIM29 protected the mice from this developing lethality. Additionally, TRIM29-/- mice have lower titers of reovirus in the heart, intestine, spleen, liver, and brain because of elevated production of type I IFN. Mechanistically, TRIM29 was shown to interact with MAVS and subsequently induce its K11-linked ubiquitination and degradation. Taken together, TRIM29 regulates negatively the host innate immune response to RNA virus, which could be employed by RNA viruses for viral pathogenesis.

TRIM29 suppresses the innate immune response to RNA virus

Abstract The innate immunity is critically important in protection against virus infections, and in the case of RNA viral infections, the signaling mechanisms that initiate robust protective innate immunity without triggering autoimmune inflammation remain incompletely defined. We have previously found that TRIM29 is constitutively expressed in alveolar macrophages and plays a critical role in the control of innate immunity in respiratory tract. Also, we have shown that TRIM29 is highly expressed in human airway epithelial cells and promotes DNA virus infections by inhibiting innate immune response. Here, we found the E3 ligase TRIM29 was specifically expressed in poly I:C stimulated human myeloid dendritic cells (mDCs). The induced TRIM29 played a negative role in type I interferon (IFN) production in response to poly I:C or dsRNA virus reovirus infection. Importantly, the challenge of wildtype mice with reovirus led to lethal infection. In contrast, deletion of TRIM29 protected the mice from this developing lethality. Additionally, TRIM29−/− mice have lower titers of reovirus in the heart, intestine, spleen, liver, and brain due to elevated production of type I IFN. Mechanistically, TRIM29 was shown to interact with MAVS and subsequently induce its K11-linked ubiquitination and degradation. Taken together, TRIM29 regulates negatively the host innate immune response to RNA virus, which could be employed by RNA viruses for immune evasion.

Human beta defensin 3 alters matrix metalloproteinase production in human dendritic cells exposed to Porphyromonas gingivalis hemagglutinin B.

Matrix metalloproteinases (MMPs) are zinc- or calcium-dependent proteinases involved in normal maintenance of extracellular matrix. When elevated, they contribute to the tissue destruction seen in periodontal disease. Recently, we found that human beta defensin 3 (HBD3), a cationic antimicrobial peptide, alters chemokine and proinflammatory cytokine responses in human myeloid dendritic cells exposed to Porphyromonas gingivalis hemagglutinin B (HagB). In this study, the hypotheses that HagB induces MMP production in dendritic cells and that HBD3 mixed with HagB prior to treatment alters HagB-induced MMP profiles were tested. Dendritic cells were exposed to 0.2 μM HagB alone and HagB + HBD3 (0.2 or 2.0 μM) mixtures. After 16hours, concentrations of MMPs in cell culture media were determined with commercial multiplex fluorescent bead-based immunoassays. An integrated cell network was used to identify potential HagB-induced signaling pathways in dendritic cells leading to the production of MMPs. 0.2 μM HagB induced MMP1, -2, -7, -9, and -12 responses in dendritic cells. 0.2 μM HBD3 enhanced the HagB-induced MMP7 response (P<0.05) and 2.0 μM HBD3 attenuated HagB-induced MMP1, -7, and -9 responses (P<0.05). The MMP12 response was not affected. In the predicted network, MMPs are produced via activation of multiple pathways. Signals converge to activate numerous transcription factors, which transcribe different MMPs. HagB was an MMP stimulus and HBD3 was found to decrease HagB-induced MMP1, -7, and -9 responses in dendritic cells at 16hours, an observation that suggests HBD3 can alter microbial antigen-induced production of MMPs.

IL10 Release upon PD-1 Blockade Sustains Immunosuppression in Ovarian Cancer.

Ligation of programmed cell death-1 (PD-1) in the tumor microenvironment is known to inhibit effective adaptive antitumor immunity. Blockade of PD-1 in humans has resulted in impressive, durable regression responses in select tumor types. However, durable responses have been elusive in ovarian cancer patients. PD-1 was recently shown to be expressed on and thereby impair the functions of tumor-infiltrating murine and human myeloid dendritic cells (TIDC) in ovarian cancer. In the present work, we characterize the regulation of PD-1 expression and the effects of PD-1 blockade on TIDC. Treatment of TIDC and bone marrow-derived dendritic cells (DC) with IL10 led to increased PD-1 expression. Both groups of DCs also responded to PD-1 blockade by increasing production of IL10. Similarly, treatment of ovarian tumor-bearing mice with PD-1 blocking antibody resulted in an increase in IL10 levels in both serum and ascites. While PD-1 blockade or IL10 neutralization as monotherapies were inefficient, combination of these two led to improved survival and delayed tumor growth; this was accompanied by augmented antitumor T- and B-cell responses and decreased infiltration of immunosuppressive MDSC. Taken together, our findings implicate compensatory release of IL10 as one of the adaptive resistance mechanisms that undermine the efficacy of anti-PD-1 (or anti-PD-L1) monotherapies and prompt further studies aimed at identifying such resistance mechanisms. Cancer Res; 77(23); 6667-78. ©2017 AACR.

Urban particulate matter stimulation of human dendritic cells enhances priming of naive CD8 T lymphocytes.

SummaryEpidemiological studies have consistently shown associations between elevated concentrations of urban particulate matter (UPM) air pollution and exacerbations of asthma and chronic obstructive pulmonary disease, which are both associated with viral respiratory infections. The effects of UPM on dendritic cell (DC) ‐stimulated CD4 T lymphocytes have been investigated previously, but little work has focused on CD8 T‐lymphocyte responses despite their importance in anti‐viral immunity. To address this, we examined the effects of UPM on DC‐stimulated naive CD8 T‐cell responses. Expression of the maturation/activation markers CD83, CCR7, CD40 and MHC class I on human myeloid DCs (mDCs) was characterized by flow cytometry after stimulation with UPM in vitro in the presence/absence of granulocyte–macrophage colony‐stimulating factor (GM‐CSF). The capacity of these mDCs to stimulate naive CD8 T‐lymphocyte responses in allogeneic co‐culture was then assessed by measuring T‐cell cytokine secretion using cytometric bead array, and proliferation and frequency of interferon‐γ (IFN‐γ)‐producing T lymphocytes by flow cytometry. Treatment of mDCs with UPM increased expression of CD83 and CCR7, but not MHC class I. In allogeneic co‐cultures, UPM treatment of mDCs enhanced CD8 T‐cell proliferation and the frequency of IFN‐γ + cells. The secretion of tumour necrosis factor‐α, interleukin‐13, Granzyme A and Granzyme B were also increased. GM‐CSF alone, and in concert with UPM, enhanced many of these T‐cell functions. The PM‐induced increase in Granzyme A was confirmed in a human experimental diesel exposure study. These data demonstrate that UPM treatment of mDCs enhances priming of naive CD8 T lymphocytes and increases production of pro‐inflammatory cytokines. Such UPM‐induced stimulation of CD8 cells may potentiate T‐lymphocyte cytotoxic responses upon concurrent airway infection, increasing bystander damage to the airways.

Monomethyl fumarate treatment impairs maturation of human myeloid dendritic cells and their ability to activate T cells

Background: Dimethyl fumarate (DMF) and its active metabolite monomethyl fumarate (MMF) effectively lead to reduction in disease relapses and active magnetic resonance imaging (MRI) lesions. DMF and MMF are known to be effective in modulating T- and B-cell responses; however, their effect on the phenotype and function of human myeloid dendritic cells (mDCs) is not fully understood. Objective: To investigate the role of MMF on human mDCs maturation and function. Methods: mDCs from healthy controls were isolated and cultured in vitro with MMF. The effect of MMF on mDC gene expression was determined by polymerase chain reaction (PCR) array after in vitro MMF treatment. The ability of mDCs to activate T cells was assessed by in vitro co-culture system. mDCs from DMF-treated multiple sclerosis (MS) patients were analyzed by flow cytometry and PCR. Results: MMF treatment induced a less mature phenotype of mDCs with reduced expression of major histocompatibility complex class II (MHC-II), co-stimulatory molecules CD86, CD40, CD83, and expression of nuclear factor κB (NF-κB) subunits RELA and RELB. mDCs from DMF-treated MS patients also showed the same immature phenotype. T cells co-cultured with MMF-treated mDCs showed reduced proliferation with decreased production of interferon gamma (IFN-γ), interleukin-17 (IL-17), and granulocyte-macrophage colony-stimulating factor (GM-CSF) compared to untreated cells. Conclusion: We report that MMF can modulate immune response by affecting human mDC function.

Human innate responses and adjuvant activity of TLR ligands in vivo in mice reconstituted with a human immune system.

TLR ligands (TLR-Ls) represent a class of novel vaccine adjuvants. However, their immunologic effects in humans remain poorly defined in vivo. Using a humanized mouse model with a functional human immune system, we investigated how different TLR-Ls stimulated human innate immune response in vivo and their applications as vaccine adjuvants for enhancing human cellular immune response. We found that splenocytes from humanized mice showed identical responses to various TLR-Ls as human PBMCs in vitro. To our surprise, various TLR-Ls stimulated human cytokines and chemokines differently in vivo compared to that in vitro. For example, CpG-A was most efficient to induce IFN-α production in vitro. In contrast, CpG-B, R848 and Poly I:C stimulated much more IFN-α than CpG-A in vivo. Importantly, the human innate immune response to specific TLR-Ls in humanized mice was different from that reported in C57BL/6 mice, but similar to that reported in nonhuman primates. Furthermore, we found that different TLR-Ls distinctively activated and mobilized human plasmacytoid dendritic cells (pDCs), myeloid DCs (mDCs) and monocytes in different organs. Finally, we showed that, as adjuvants, CpG-B, R848 and Poly I:C can all enhance antigen specific CD4+ T cell response, while only R848 and Poly I:C induced CD8+ cytotoxic T cells response to a CD40-targeting HIV vaccine in humanized mice, correlated with their ability to activate human mDCs but not pDCs. We conclude that humanized mice serve as a highly relevant model to evaluate and rank the human immunologic effects of novel adjuvants in vivo prior to testing in humans.

Immunomodulatory effects of heat-killed Mycobacterium obuense on human blood dendritic cells.

Heat-killed (HK) Mycobacterium obuense is a novel immunomodulator, currently undergoing clinical evaluation as an immunotherapeutic agent in the treatment of cancer. Here, we examined the effect of invitro exposure to HK M. obuense on the expression of different categories of surface receptors on human blood myeloid (m) and plasmacytoid (p) DCs. Moreover, we have characterized the cytokine and chemokine secretion patterns of purified total blood DCs stimulated with HK M. obuense. HK M. obuense significantly up-regulated the expression of CD11c, CD80, CD83, CD86, CD274 and MHC class II in whole-blood mDCs and CD80, CD123 and MHC class II in whole-blood pDCs. Down-regulation of CD195 expression in both DC subpopulations was also noted. Further analysis showed that HK M. obuense up-regulated the expression of CD80, CD83 and MHC class II on purified blood DC subpopulations. TLR2 and TLR1 were also identified to be engaged in mediating the HK M. obuense-induced up-regulation of surface receptor expression on whole blood mDCs. In addition, our data demonstrated that HK M. obuense augmented the secretion of CCL4, CCL5, CCL22, CXCL8, IL-6, IL-12p40 and TNF-α by purified total blood DCs. Taken together, our data suggest that HK M. obuense exerts potent differential immunomodulatory effects on human DC subpopulations.

Daphnoretin modulates differentiation and maturation of human dendritic cells through down-regulation of c-Jun N-terminal kinase

Daphnoretin, an active constituent of Wikstroemia indica C.A. Meys, has been shown possessing anti-cancer activity. In this study, we examined the effect of daphnoretin on differentiation and maturation of human myeloid dendritic cells (DCs). After treatment with daphnoretin (0, 1.1, 3.3, 10 and 30μM) to initiate monocytes, the recovery rate of DCs was reduced in a dose-dependent manner. The mature DCs differentiated in the presence of daphnoretin had fewer and shorter dendrites. Daphnoretin modulated DCs differentiation and maturation in terms of lower expression of CD1a, CD40, CD83, DC-SIGN, and HLA-DR. Daphnoretin inhibited the allostimulatory activity of DCs on proliferation of naive CD4+CD45+RA+ T cell. On the mitogen-activated protein kinase, daphnoretin down-regulated the lipopolysaccharide-augmented expression of phosphorylated c-Jun N-terminal kinase (pJNK), but not p38 and extracellular signal-regulated kinase 1/2 (ERK1/2). Activation of JNK by anisomycin reversed the effect of daphnoretin on daphnoretin-inhibited pJNK expression and dendrite formation of DCs. In disease model related to maturation of DCs, daphnoretin suppressed the acute rejection of skin allografts in mice. Our results suggest that daphnoretin modulated differentiation and maturation of DCs toward a state of atypical maturation with impaired allostimulatory function and this effect may go through down-regulation of phosphorylated JNK.