Activation Of Plasmacytoid Dendritic Cells Research Articles

The metabolic modulator metformin affects the activation and survival of murine dendritic cell subsets

Abstract Unique immunometabolic pathways control the ability of dendritic cell subsets to activate, and metabolic modulators are proposed as therapeutic candidates in cancer and autoimmunity, although their effects on specific immune cells are not fully known. The metabolic inhibitor metformin, the first-choice oral treatment for type II diabetes, has many effects on immunometabolism, including the inhibition of complex I of oxidative phosphorylation. Metformin was shown to decrease the severity of autoimmunity in murine models by inhibiting the activation of T cells. Moreover, it can diminish tumor growth through affecting the polarization of tumor-infiltrating macrophages. Here, we determined the effects of metformin on three subsets of dendritic cells that are proposed to have different energy requirements for activation. Upon TLR stimulation, we found that metformin does not affect the activation of the inflammatory GM-CSF-dependent dendritic cells (iDCs) or the Flt3-L-dependent conventional dendritic cells (cDCs), which rely on an immuno-metabolic shift to glycolysis to fully activate and express costimulatory molecules and pro-inflammatory cytokines, but it decreased cDC survival at resting state. In contrast, we found that metformin inhibited the activation of plasmacytoid dendritic cells (pDCs), which requires both an increase in oxidative phosphorylation and glycolysis for activation. Our studies provide a new layer of complexity in the potential of metformin as treatment in autoimmunity and cancer by showing that this drug can inhibit the activation of pDCs and also eliminate resting cDCs, therefore altering in opposite directions the impact of these innate cell subsets on the immune response.

Autologous tumor cell vaccination combined with systemic CpG-B and IFN-\u03b1 promotes immune activation and induces clinical responses in patients with metastatic renal cell carcinoma: a phase II trial

In this study the toxicity and efficacy of an irradiated autologous tumor cell vaccine (ATV) co-injected with a class-B CpG oligodeoxynucleotide (CpG-B) and GM-CSF, followed by systemic CpG-B and IFN-α administration, were examined in patients with metastatic renal cell carcinoma (mRCC). A single-arm Phase II trial was conducted, in which patients with mRCC were intradermally injected with a minimum of three whole-cell vaccines containing 0.7–1.3 × 107 irradiated autologous tumor cells (ATC), admixed with 1 mg CpG-B and 100 µg GM-CSF, followed by bi-weekly s.c. injections with 8 mg CpG-B and s.c. injections with 6 MU IFN-α three times per week. Fifteen patients were treated according to the protocol. Treatment was well tolerated. Objective clinical responses occurred in three patients, including one long-term complete response. Disease stabilization occurred in another three patients. Positive delayed type hypersensitivity (DTH) responses to ATC were absent before treatment but present in 13 out of 15 patients during treatment. Immune monitoring revealed activation of plasmacytoid dendritic cells, non-classical monocytes and up-regulation of both PD-1 and CTLA4 on effector T cells upon treatment. Moreover, a pre-existing ex vivo IFN-γ response to ATC was associated with clinical response. ATV combined with systemic CpG-B and IFN-α is tolerable, safe, immunogenic and able to elicit anti-tumor responses in patients with mRCC. Immune activation and treatment-induced up-regulation of PD-1 and CTLA4 on circulating T cells further suggest an added benefit of combining this approach with immune checkpoint blockade [added]

Multifunctional nanoparticles based on a polymeric copper chelator for combination treatment of metastatic breast cancer

Copper plays an important role in tumor growth and metastasis. Copper chelation has been confirmed to be an effective strategy for breast cancer therapy through antiangiogenesis. In this work, a copper chelating coil-comb block copolymer RGD-PEG-b-PGA-g-(TETA-DTC-PHis) (RPTDH) was synthesized and used to prepare nanoparticles for loading resiquimod (R848), a TLR7 and TLR8 agonist, thus to combine antiangiogenesis and immune activation to treat breast cancer. RPTDH has strong copper-chelating ability and could self-assemble to form spherical nanoparticles with significant pH-sensitivity. R848 was efficiently loaded into RPTDH nanoparticles and exhibited greatly accelerated releases in weakly acid media simulating tumor microenvironment. RPTDH/R848 nanoparticles significantly inhibited the mobility, invasion and vascular tube formation of HUVECs via copper chelation, demonstrating their strong antiangiogenic activity in vitro. Furthermore, RPTDH/R848 nanoparticles remarkably induced the maturation and activation of human plasmacytoid dendritic CAL-1 cells, indicating their immune-activation ability. In breast tumor-bearing mice, RPTDH/R848 nanoparticles displayed excellent targeting ability for both primary breast tumor and lung metastases, and furthermore dramatically suppressed tumor growth and metastasis through copper deficiency-triggered antiangiogenesis and R848-induced immune activation. In summary, RPTDH/R848 nanoparticles can be used as an therapeutic agent against metastatic breast cancer through combining antiangiogenesis and immune activation.

Myeloid and lymphoid activation markers in AIDS and non-AIDS presenters

HIV infection is characterized by a state of chronic activation of the immune system, which is not completely reversed by antiretroviral treatment (ART). The aim of this study was to assess myeloid and lymphoid activation markers during HIV infection, before and one year after ART initiation, in AIDS and non-AIDS presenters. Treatment naïve HIV positive patients were enrolled in this study. Myeloid dendritic cell (mDC), plasmacytoid dendritic cell (pDC), slanDC, monocyte and T-lymphocyte cell counts and activation status, were assessed by flow cytometry in peripheral blood samples. Soluble (s)CD14 and sCD163 were assessed in plasma samples using ELISA assays. Statistical analyses were performed using GraphPad Prism and Minitab Express.Thirty-four ART naïve HIV-1 infected subjects were enrolled in this study (22 non-AIDS and 12 AIDS presenters). Seventeen healthy donors (HD) were included as control group. Although circulating mDC levels resulted unchanged, HLA-DR expression was decreased on mDCs of HIV positive subjects compared to HD (p < 0,0001). AIDS presenters showed the lowest level of expression of HLA-DR on mDCs. Circulating levels of pDCs were decreased in HIV patients compared to HD (p < 0,001), without any changes in HLA-DR expression. SlanDC cell counts were extremely reduced in AIDS presenters, compared to non-AIDS presenters and HD (p < 0,01 and p < 0,0001, respectively) and showed higher HLA-DR expression in HIV patients compared to HD (p < 0,01). Intermediate monocyte (IM) cell counts were increased in AIDS and non-AIDS presenters compared to HD (p < 0,001 and p < 0,001 respectively). Furthermore, IM expansion was directly correlated to HIV viral load (p = 0,036) and independent from CD4 cell counts and activation levels. Plasma concentrations of sCD14 and sCD163 resulted increased in HIV infected subjects compared to HD (p < 0,0001 and p < 0,001), with the highest levels observed in AIDS presenters. After 1 year, ART was able to increase pDC and decrease IM absolute cell counts and modify HLA-DR expression on mDCs and slanDCs, approaching the levels observed in HD. ART reduced also CD4 and CD8 activation levels. In conclusion, in untreated HIV infected subjects circulating dendritic cells resulted altered either in numbers or in HLA-DR expression, especially in AIDS presenters. IM absolute counts were equally increased in AIDS and non-AIDS presenters. ART was able to reduce myeloid and lymphoid inflammation in both advanced and non-advanced HIV patients, confirming the role of ART in hampering disease progression and immune activation associated non-AIDS events.

Molecular dissection of plasmacytoid dendritic cell activation in vivo during a viral infection

Plasmacytoid dendritic cells (pDC) are the major source of type I interferons (IFN‐I) during viral infections, in response to triggering of endosomal Toll‐like receptors (TLRs) 7 or 9 by viral single‐stranded RNA or unmethylated CpG DNA, respectively. Synthetic ligands have been used to disentangle the underlying signaling pathways. The adaptor protein AP3 is necessary to transport molecular complexes of TLRs, synthetic CpG DNA, and MyD88 into endosomal compartments allowing interferon regulatory factor 7 (IRF7) recruitment whose phosphorylation then initiates IFN‐I production. High basal expression of IRF7 by pDC and its further enhancement by positive IFN‐I feedback signaling appear to be necessary for robust cytokine production. In contrast, we show here that in vivo during mouse cytomegalovirus (MCMV) infection pDC produce high amounts of IFN‐I downstream of the TLR9‐to‐MyD88‐to‐IRF7 signaling pathway without requiring IFN‐I positive feedback, high IRF7 expression, or AP3‐driven endosomal routing of TLRs. Hence, the current model of the molecular requirements for professional IFN‐I production by pDC, established by using synthetic TLR ligands, does not strictly apply to a physiological viral infection.

Abstract 614: Resiquimod, a Toll-like receptor agonist promotes melanoma regression by enhancing plasmacytoid dendritic cells and T cytotoxic activity as a vaccination adjuvant and by direct tumor application

Abstract Introduction: Cancer immunotherapy is a modern strategy aiming at restoring the capacity of the immune system to target tumors in cancer patients. Toll-like receptor (TLR) agonists may enhance vaccination or direct immune activation at the tumor microenvironment. This clinical trial evaluated the biologic effects of Resiquimod, a TLR agonist that can activate both myeloid (TLR 8) and plasmacytoid (TLR 7) dendritic cells, on advanced stage melanoma. Methods: Subjects with in-transit melanoma metastases or high risk for recurrence and appropriate HLA were treated with peptide vaccination (class 1 restricted peptide GP100(g209-2m) and, if HLA-DP4+, class 2 restricted peptide MAGE-3243-258). Half of the patients were randomized to receive Resiquimod as an adjuvant applied to the GP100 vaccination site. Subjects with in-transit disease were then treated with resiquimod topically on half of the target lesions. To evaluate the T cell function, fresh PBMC and single cell tumor suspension were analyzed by flow cytometry using gp100-specific dextramer staining. RNA from the vaccination site was also analyzed using real-time PCR. Results: All patients (n=47) underwent GP100(g209-2m) vaccination, a majority (39) also received the MAGE-3243-258 peptide. Type 1 interferon pathway protein profiles of vaccination sites showed activation of plasmacytoid dendritic cells in patients with Resiquimod, but not in its absence. Nineteen subjects had in-transit disease at entry into the trial. In response to peptide vaccination alone, tumor regression was more likely in patients who received Resiquimod (group A) compared to those who did not (group B). (4/9 vs 0/10). In group A, 5 patients continued treatment with Resiquimod topically on the tumors, and all had tumor response (4PR, 1CR). In group B, 5 continued to tumoral resiquimod and 3 had regression (3 PR). Type I interferon (as measured by MxA and IRF7) IFN-gamma and TNF-alpha increased at the vaccination site 24 hrs after vaccination only at the sites where Resiquimod was applied. In blood, Resiquimod increased gp100-specific CD8 T cells frequency at week 8 (p=0.03) only in patients who received Resiquimod at the vaccination site. Conclusions: Resiquimod activates plasmacytoid dendritic cells at a peptide vaccination site and augments peptide vaccination sufficiently to mediate regression of in-transit melanoma metastasis. Resiquimod on in-transit melanoma, in vaccinated hosts, drives regression of metastases, regardless of previous exposure at vaccination site. An increased amount of cytokines such type I interferon, IFN-gamma, TNF-alpha, and T specific cytotoxic frequency were increased at the vaccination site after patients received Resiquimod. Citation Format: Jorge A. Borin Scutti, Luis M. Vence, Richard E. Royal, Tara C. Wray, Janice N. Cormier, Jeffrey E. Lee, Anthony Lucci, Jeffrey E. Gershenwald, Merrick I. Ross, Jennifer Wargo, Karen A. Millerchip, Rodabe N. Amaria, Michael A. Davis, Adi Diab, Isabella C. Glitza, Wen Hwu, Sapna Patel, Scott E. Woodman, Willem W. Overwijk, Patrick Hwu. Resiquimod, a Toll-like receptor agonist promotes melanoma regression by enhancing plasmacytoid dendritic cells and T cytotoxic activity as a vaccination adjuvant and by direct tumor application [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 614.

TLR7 polymorphism, sex and chronic HBV infection influence plasmacytoid DC maturation by TLR7 ligands

TLR7 agonists are of high interest for the treatment of cancer, auto-immunity and chronic viral infections. They are known to activate plasmacytoid dendritic cells (pDCs) to produce high amounts of Type I Interferon (IFN) and to facilitate T and B cell responses, the latter with the help of maturation markers such as CD40, CD80 and CD86. The TLR7 single nucleotide polymorphism (SNP) rs179008 (GLn11Leu), sex and chronic viral infection have all been reported to influence pDC IFN production. It is unknown, however, whether these factors also influence pDC phenotypic maturation and thereby IFN-independent pDC functions. Furthermore, it is unclear whether SNP rs179008 influences HBV susceptibility and/or clearance.Here we investigated whether the SNP rs179008, sex and HBV infection affected phenotypic maturation of pDCs from 38 healthy individuals and 28 chronic HBV patients. In addition, we assessed SNP prevalence in a large cohort of healthy individuals (n = 231) and chronic HBV patients (n = 1054).Consistent with previous reports, the rs179008 variant allele was largely absent in Asians and more prevalent in Caucasians. Among Caucasians, the SNP was equally prevalent in healthy and chronically infected males. The SNP was, however, significantly more prevalent in healthy females than in those with chronic HBV infection (42 versus 28%), suggesting that in females it may offer protection from chronic infection. Ex vivo experiments demonstrated that induction of the co-stimulatory molecules CD40 and CD86 by TLR7 ligands, but not TLR9 ligands, was augmented in pDCs from healthy SNP-carrying females. Furthermore, CD80 and CD86 upregulation was more pronounced in females independent of the SNP. Lastly, our data suggested that chronic HBV infection impairs pDC maturation. These findings provide insight into factors determining TLR7 responses, which is important for further clinical development of TLR7-based therapies.

Plasmacytoid dendritic cells control dengue and Chikungunya virus infections via IRF7-regulated interferon responses.

Type I interferon (IFN-I) responses are critical for the control of RNA virus infections, however, many viruses, including Dengue (DENV) and Chikungunya (CHIKV) virus, do not directly activate plasmacytoid dendritic cells (pDCs), robust IFN-I producing cells. Herein, we demonstrated that DENV and CHIKV infected cells are sensed by pDCs, indirectly, resulting in selective IRF7 activation and IFN-I production, in the absence of other inflammatory cytokine responses. To elucidate pDC immunomodulatory functions, we developed a mouse model in which IRF7 signaling is restricted to pDC. Despite undetectable levels of IFN-I protein, pDC-restricted IRF7 signaling controlled both viruses and was sufficient to protect mice from lethal CHIKV infection. Early pDC IRF7-signaling resulted in amplification of downstream antiviral responses, including an accelerated natural killer (NK) cell-mediated type II IFN response. These studies revealed the dominant, yet indirect role of pDC IRF7-signaling in directing both type I and II IFN responses during arbovirus infections.

Neutrophil extracellular trap release is associated with antinuclear antibodies in systemic lupus erythematosus and anti-phospholipid syndrome.

Increased release of neutrophil extracellular traps (NETs) is implicated in the activation of plasmacytoid dendritic cells, vascular disease and thrombosis in SLE and APS. However, studies comparing NET release between patients with SLE and APS are lacking. Here we evaluated plasma-induced NET release in a large cohort of patients with SLE, SLE + APS and primary APS in relation to clinical and serological parameters. Neutrophils from healthy controls were exposed to plasma of heterologous healthy controls (n = 27) or SLE (n = 55), SLE + APS (n = 38) or primary APS (PAPS) (n = 28) patients and NET release was quantified by immunofluorescence. In a subset of SLE patients, NET release was assessed in longitudinal samples before and after a change in treatment. Plasma-induced NET release was increased in SLE and APS patients, with the highest NET release found in patients with SLE (±APS). Plasma of 60% of SLE, 61% of SLE + APS and 45% of PAPS patients induced NET release. NET release did not correlate with disease activity in SLE or APS. However, increased levels of anti-nuclear and anti-dsDNA autoantibodies were associated with increased NET release in SLE and APS. Only in SLE patients, elevated NET release and an increased number of low-density granulocytes were associated with a high IFN signature. Increased NET release is associated with autoimmunity and inflammation in SLE and APS. Inhibition of NET release thus could be of potential benefit in a subset of patients with SLE and APS.

IgE in lupus pathogenesis: Friends or foes?

Systemic lupus erythematosus (SLE) is a complex autoimmune disease involving multiple immunological pathways. Recently, several studies have suggested an implication of Immunoglobulin E (IgE) in the pathophysiology of SLE. In the Lyn-/- and FcγIIB-/-.Yaa lupus mouse models, autoreactive IgE activate basophils, and promote a Th2 environment with, subsequently, production of autoantibodies by plasma cells. Autoreactive IgE has been also shown to play a role in the activation of human plasmacytoid dendritic cells (pDCs), in synergy with IgG, which results in an increase of interferon-alpha (IFN-α) production. In contrast, a protective effect of total non-autoreactive IgE has also been suggested, through a decreased ability of FcεRI-triggered pDCs to secrete IFN-α. This review summarizes in a comprehensive manner the emerging recent literature in the field, and propose new concepts to reconcile the observations.

GS-9620 inhibits enterovirus 71 replication mainly through the NF-κB and PI3K-AKT signaling pathways

Human enterovirus 71 (EV71) is the second most common cause of hand, foot, and mouth disease (HFMD), which can occur as a severe epidemic especially among children under 5-years old. New and improved treatment strategies to control EV71 infection are therefore urgently required. The heterocyclic compound GS-9620, a potent and selective agonist of Toll-like receptor 7 (TLR7), has been reported to activate plasmacytoid dendritic cells (pDCs), and suppress HBV as well as HIV replication. In this study, we indicated that GS-9620 also could inhibit EV71 replication in the mouse model of EV71 infection. With three-days treatment after EV71 infection, the levels of proinflammatory cytokines/chemokines, like IFN-α, IFN-γ and MCP-1, were sharply reduced in serum compared to those without treatment. Furthermore, GS-9620 activated TLR7 in the limb muscle cells, which stimulated the NF-κB and PI3K/AKT signaling pathways. When NF-κB or PI3K/AKT inhibitors were used, the antiviral effect of the GS-9620 was impacted. Overall, our data implied GS-9620 probably activates NF-κB and PI3K/AKT signaling pathways to clear the virus.

Systemic administration of a TLR7 agonist attenuates regulatory T cells by dendritic cell modification and overcomes resistance to PD-L1 blockade therapy.

Research on immune checkpoint blockade therapy has made great progress in cancer immunotherapy, but the number of patients who benefit from this therapy remains limited. In this study, we examined the effects of monotherapy with systemic low-dose resiquimod, a synthesized TLR7 agonist, and examined its combined effects with PD-L1 blockade in two PD-L1 blockade-resistant tumor models (SCCVII and Colon 26). Resiquimod monotherapy in SCCVII tumors, representing impaired CD8+ T cell function and accelerated regulatory T cells (Tregs) within the tumors, efficiently reduced tumor growth with more recruitment of CD8+ T cells and a reduction of Treg. The results of resiquimod monotherapy in Colon 26, representing impaired Treg recruitment, were inferior to that in SCCVII. Combined resiquimod treatment with PD-L1 blockade exerted clear additional effects, as it was associated with reduced tumor size, attenuation of Tregs, and an increased ratio of CD8+ T cells/Tregs in both tumors. Systemic administration of low-dose resiquimod induced a transient and rapid activation of plasmacytoid and conventional dendritic cells, resulting in enhanced priming of T cells in regional lymph nodes. Experiments with more limited doses of resiquimod that did not yield beneficial effects after single treatment, showed additional effects to PD-L1 blockade and comparable antitumor effects when the frequency of anti-PD-L1 therapy was decreased. Our results suggest that systemic administration of low-dose resiquimod is useful as a companion drug to PD-1/PD-L1 blockade therapy.

Safety Evaluation of Excessive Intake of &amp;lt;i&amp;gt;Lactococcus lactis&amp;lt;/i&amp;gt; Subsp. &amp;lt;i&amp;gt;lactis&amp;lt;/i&amp;gt; JCM 5805: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Trial

Background/Aims: Administration of a lactic acid bacterial strain, Lactococcus lactis subsp. lactis JCM 5805 (LC-Plasma), is reported to prevent viral infection via activation of plasmacytoid dendritic cells in mouse and human studies. As it is assumed that LC-Plasma is taken in excess when it is commercially provided as a supplement, we conducted a trial using capsules to give 250 mg LC-Plasma (5 times the effective anti-viral dose) every day for four weeks to healthy volunteers to investigate the safety of excessive intake of LC-Plasma. Trial Design: A randomized, double-blind, placebo-controlled, parallel-group trial was conducted. Methods: Forty healthy subjects were randomly assigned to the LC-Plasma group (daily intake of five capsules containing 50 mg heat-killed LC-Plasma cells per capsule) or the placebo group (daily intake of five placebo capsules with no LC-Plasma). Physical, hematological, biochemical and urinary examinations and medical interviews were used to evaluate safety. Results: No abnormal differences were observed after excessive intake of LC-Plasma capsules when compared to the intake of placebo capsules. Conclusions: There are no safety concerns associated with the excessive intake of heat-killed LC-Plasma capsules.

Building and Crossing the Translational Bridge: 2016Alopecia Areata Research Summit Highlights.

Alopecia areata (AA) is a common autoimmune skin disease that results in the loss of hair on the scalp and elsewhere on the body and affects over 146 million people worldwide at some point in their lives. Founded in 1981, the National Alopecia Areata Foundation is a nonprofit organization that supports research to find a cure or acceptable treatment for AA, supports those with the disease, and educates the public about AA. The National Alopecia Areata Foundation conducts research summits every 2 years to review progress and create new directions in its funded and promoted research. The Foundation brings together scientists from all disciplines to get a broad and varied perspective. These AA research summits are part of the Foundation's main strategic initiative, the AA Treatment Development Program, to enhance the understanding of AA and accelerate progress toward a viable treatment.

Antifungal Activity of Plasmacytoid Dendritic Cells and the Impact of Chronic HIV Infection.

Due to the effectiveness of combined antiretroviral therapy, people living with HIV can control viral replication and live longer lifespans than ever. However, HIV-positive individuals still face challenges to their health and well-being, including dysregulation of the immune system resulting from years of chronic immune activation, as well as opportunistic infections from pathogenic fungi. This review focuses on one of the key players in HIV immunology, the plasmacytoid dendritic cell (pDC), which links the innate and adaptive immune response and is notable for being the body’s most potent producer of type-I interferons (IFNs). During chronic HIV infection, the pDC compartment is greatly dysregulated, experiencing a substantial depletion in number and compromise in function. This immune dysregulation may leave patients further susceptible to opportunistic infections. This is especially important when considering a new role for pDCs currently emerging in the literature: in addition to their role in antiviral immunity, recent studies suggest that pDCs also play an important role in antifungal immunity. Supporting this new role, pDCs express C-type lectin receptors including dectin-1, dectin-2, dectin-3, and mannose receptor, and toll-like receptors-4 and -9 that are involved in recognition, signaling, and response to a wide variety of fungal pathogens, including Aspergillus fumigatus, Cryptococcus neoformans, Candida albicans, and Pneumocystis jirovecii. Accordingly, pDCs have been demonstrated to recognize and respond to certain pathogenic fungi, measured via activation, cytokine production, and fungistatic activity in vitro, while in vivo mouse models indicated a strikingly vital role for pDCs in survival against pulmonary Aspergillus challenge. Here, we discuss the role of the pDC compartment and the dysregulation it undergoes during chronic HIV infection, as well as what is known so far about the role and mechanisms of pDC antifungal activity.

Activation of plasmacytoid dendritic cells by apoptotic particles-mechanism for the loss of immunological tolerance in Sjögren's syndrome.

Sjögren's syndrome (SS) is a common autoimmune disease targeting salivary and lacrimal glands. It is strongly female-dominant, characterized by low oestrogen levels combined with a local intracrine dihydrotestosterone defect. We hypothesized that these hormonal deficits lead to increased apoptosis of the epithelial cells and plasmacytoid dendritic cell (pDC)-mediated proinflammatory host responses. Expression of Toll-like receptors (TLRs)-7 and -9 and cytokine profiles was studied in pDCs treated with apoptotic particles collected in consecutive centrifugation steps of media from apoptotic cells. Expression and localization of SS autoantigens in these particles was also analysed. Furthermore, the effects of sex steroids were studied in pDCs cultured with several concentrations of dihydrotestosterone and 17-β-oestradiol, and in saliva of patient treated with dehydroepiandrosterone. Apoptosis of the epithelial cells led to cleavage and translocation of SS-autoantigens, α-fodrin and SS-A, into apoptotic particles. The apoptosis-induced apoptotic particles also contained another SS-autoantigen, hy1-RNA. These particles were internalized by pDCs in a size-dependent manner and affected TLR-7 and -9 expression and the production of proinflammatory cytokines. The analysed androgens protected cells from apoptosis, influenced redistribution of autoantigens and diminished the apoptotic particle-stimulated increase of the TLRs in pDCs. Our findings suggest that the formation of apoptotic particles may play a role in loss of immune tolerance, manifested by production of autoantibodies and the onset of autoinflammation in SS.

Therapeutic Modulation of Plasmacytoid Dendritic Cells in Experimental Arthritis.

The role of plasmacytoid dendritic cells (PDCs) and type I interferons (IFNs) in rheumatoid arthritis (RA) remains a subject of controversy. This study was undertaken to explore the contribution of PDCs and type I IFNs to RA pathogenesis using various animal models of PDC depletion and to monitor the effect of localized PDC recruitment and activation on joint inflammation and bone damage. Mice with K/BxN serum-induced arthritis, collagen-induced arthritis, and human tumor necrosis factor transgene insertion were studied. Symptoms were evaluated by visual scoring, quantification of paw swelling, determination of cytokine levels by enzyme-linked immunosorbent assay, and histologic analysis. Imiquimod-dependent therapeutic effects were monitored by transcriptome analysis (using quantitative reverse transcriptase-polymerase chain reaction) and flow cytometric analysis of the periarticular tissue. PDC-deficient mice showed exacerbation of inflammatory and arthritis symptoms after arthritogenic serum transfer. In contrast, enhancing PDC recruitment and activation to arthritic joints by topical application of the Toll-like receptor 7 (TLR-7) agonist imiquimod significantly ameliorated arthritis in various mouse models. Imiquimod induced an IFN signature and led to reduced infiltration of inflammatory cells. The therapeutic effects of imiquimod on joint inflammation and bone destruction are dependent on TLR-7 sensing by PDCs and type I IFN signaling. Our findings indicate that local recruitment and activation of PDCs represents an attractive therapeutic opportunity for RA patients.

The Quest for Psoriasis Autoantigens: Genetics Meets Immunology in the Melanocyte

The Quest for Psoriasis Autoantigens: Genetics Meets Immunology in the Melanocyte

Association of MicroRNA-618 Expression With Altered Frequency and Activation of Plasmacytoid Dendritic Cells in Patients With Systemic Sclerosis.

Plasmacytoid dendritic cells (PDCs) are a critical source of type I interferons (IFNs) that can contribute to the onset and maintenance of autoimmunity. Molecular mechanisms leading to PDC dysregulation and a persistent type I IFN signature are largely unexplored, especially in patients with systemic sclerosis (SSc), a disease in which PDCs infiltrate fibrotic skin lesions and produce higher levels of IFNα than those in healthy controls. This study was undertaken to investigate potential microRNA (miRNA)-mediated epigenetic mechanisms underlying PDC dysregulation and type I IFN production in SSc. We performed miRNA expression profiling and validation in highly purified PDCs obtained from the peripheral blood of 3 independent cohorts of healthy controls and SSc patients. Possible functions of miRNA-618 (miR-618) on PDC biology were identified by overexpression in healthy PDCs. Expression of miR-618 was up-regulated in PDCs from SSc patients, including those with early disease who did not present with skin fibrosis. IFN regulatory factor 8, a crucial transcription factor for PDC development and activation, was identified as a target of miR-618. Overexpression of miR-618 reduced the development of PDCs from CD34+ cells in vitro and enhanced their ability to secrete IFNα, mimicking the PDC phenotype observed in SSc patients. Up-regulation of miR-618 suppresses the development of PDCs and increases their ability to secrete IFNα, potentially contributing to the type I IFN signature observed in SSc patients. Considering the importance of PDCs in the pathogenesis of SSc and other diseases characterized by a type I IFN signature, miR-618 potentially represents an important epigenetic target to regulate immune system homeostasis in these conditions.

Neutrophil extracellular traps induced by cigarette smoke activate plasmacytoid dendritic cells

BackgroundNeutrophil extracellular traps (NETs) represent a distinct strategy by which neutrophils trap, confine and eliminate invading microorganisms. Emerging evidence suggests that NETs exert a deleterious effect to the host in...