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Abstract Background Plasmacytoid and myeloid dendritic cells play a vital role in the protection against viral infections. In COVID-19, there is an impairment of dendritic cell (DC) function and interferon secretion which has been correlated with disease severity. Results In this study, we described the frequency of DC subsets and the plasma levels of Type I (IFNα, IFNβ) and Type III Interferons (IFNλ1), IFNλ2) and IFNλ3) in seven groups of COVID-19 individuals, classified based on days since RT-PCR confirmation of SARS-CoV2 infection. Our data shows that the frequencies of pDC and mDC increase from Days 15–30 to Days 61–90 and plateau thereafter. Similarly, the levels of IFNα, IFNβ, IFNλ1, IFNλ2 and IFNλ3 increase from Days 15–30 to Days 61–90 and plateau thereafter. COVID-19 patients with severe disease exhibit diminished frequencies of pDC and mDC and decreased levels of IFNα, IFNβ, IFNλ1, IFNλ2 and IFNλ3. Finally, the percentages of DC subsets positively correlated with the levels of Type I and Type III IFNs. Conclusion Thus, our study provides evidence of restoration of homeostatic levels in DC subset frequencies and circulating levels of Type I and Type III IFNs in convalescent COVID-19 individuals.

Background: Plasmacytoid and myeloid dendritic cells play a vital role in the protection against viral infections. In COVID-19, there is an impairment of dendritic cell (DC) function and interferon secretion which has been correlated with disease severity. Results: In this study, we described the frequency of DC subsets and the plasma levels of Type I (IFNα, IFNβ) and Type III Interferons (IFNλ1), IFNλ2) and IFNλ3) in seven groups of COVID-19 individuals, classified based on days since RT-PCR confirmation of SARS-CoV2 infection. Our data shows that the frequencies of pDC and mDC increase from Days 15–30 to Days 61–90 and plateau thereafter. Similarly, the levels of IFNα, IFNβ, IFNλ1, IFNλ2 and IFNλ3 increase from Days 15–30 to Days 61–90 and plateau thereafter. COVID-19 patients with severe disease exhibit diminished frequencies of pDC and mDC and decreased levels of IFNα, IFNβ, IFNλ1, IFNλ2 and IFNλ3. Finally, the percentages of DC subsets positively correlated with the levels of Type I and Type III IFNs. Conclusion: Thus, our study provides evidence of restoration of homeostatic levels in DC subset frequencies and circulating levels of Type I and Type III IFNs in convalescent COVID-19 individuals. [ABSTRACT FROM AUTHOR]

Representing the first line of host defense against virus infections and an essential link between innate and adaptive immune response, the role of dendritic cells (DCs) in peripheral blood of juvenile-onset recurrent respiratory papillomatosis (JORRP) patients and association with disease activity were still not established. In our present study, 28 JORRP patients and 28 age and sex matched healthy controls were enrolled. The percentage, phenotype and cytokine secretion of DC and was measured by flow cytometry. Plasma cytokine were detected by the enzyme-linked immunosorbent assay (ELISA). We found that the percentage of myeloid DC (mDC) was significantly lower in JORRP patients compared to healthy controls and was negatively correlated with interval times, but not surgical times or disease onset. Moreover, the activation marker, CD40 and CD86 was significantly up-regulated on the surfaces of mDC in JORRP patients compared with healthy controls. Neither the percentage nor activation of plasmacytoid DC (pDC) showed statistical difference between JORRP patients and healthy controls. HLA-DR expression on both mDC and pDC was down-regulated in JORRP group and negatively correlated with surgical times. Antigen presenting ability of DC was greatly impaired in JORRP patients of higher number of operations and shorter interval time. Plasma IL-10 as well as IL-10 secreted by mDC was higher in JORRP patients compared with healthy control. Finally, we detected an up-regulated TLR2 and TLR4 expression on mDCs and TLR4 expression was positively correlated with HLA-DR expression on mDC of JORRP patients. Our results demonstrate an abnormal TLR2 and TLR4 expression in mDCs may contribute to suppressive immune response to HPV6 or HPV11 infection and associated with disease activity in JORRP patients. [ABSTRACT FROM AUTHOR]

Because of the potent graft-versus-tumor (GVT) effect, allogeneic stem cell transplantation (alloSCT) can be a curative therapy for hematological malignancies. However, relapse remains the most frequent cause of treatment failure, illustrating the necessity for development of adjuvant post-transplant therapies to boost GVT immunity. Dendritic cell (DC) vaccination is a promising strategy in this respect, in particular, where distinct biologic functions of naturally occurring DC subsets, i.e. myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), are harnessed. However, it is challenging to obtain high enough numbers of primary DC subsets from blood for immunotherapy due to their low frequencies. Therefore, we present here an ex vivo GMP-compliant cell culture protocol for generating different DC subsets from CD34+ hematopoietic stem and progenitor cells (HSPCs) of alloSCT donor origin. High numbers of BDCA1+ mDCs and pDCs could be generated, sufficient for multiple vaccination cycles. These HSPC-derived DC subsets were highly potent in inducing antitumor immune responses in vitro. Notably, HSPC-derived BDCA1+ mDCs were superior in eliciting T cell responses. They efficiently primed naïve T cells and robustly expanded patient-derived minor histocompatibility antigen (MiHA)-specific T cells. Though the HSPC-pDCs also efficiently induced T cell responses, they exhibited superior capacity in activating NK cells. pDC-primed NK cells highly upregulated TRAIL and possessed strong cytolytic capacity against tumor cells. Collectively, these findings indicate that HSPC-derived DC vaccines, comprising both mDCs and pDCs, may possess superior potential to boost antitumor immunity post alloSCT, due to their exceptional T cell and NK cell stimulatory capacity.

The testis has been described in animal models as a site of immune privilege, which protects spermatids against tissue damage during inflammation. Myeloid cells, including macrophages and dendritic cells (DC), are defined as key players in the testicular immune privilege in animal models. However, their distribution and frequency in human testis remain poorly described. To overcome the challenges related to tissue sampling, we obtained testicular tissue from men under hormonal therapy who elected to have sex reassignment surgery (SRS). We examined the distribution of myeloid cell populations in tissue sections using immunohistofluorescence and evaluated their relative frequencies in fresh testicular cell suspensions compared with matched blood using multi-parametric flow cytometry. We identified 4.9% of CD45 + leucocytes in testicular cell suspensions, of which 0.4% were B cells, demonstrating a low level of blood contamination. Myeloid cells (Lin − HLA-DR + ) were located in the testicular interstitium and represented a median of 23.4% of testicular leucocytes, displaying higher HLA-DR expression compared to their counterparts in blood (p = 0.001). The frequency of testicular myeloid cells was not linked with the duration of hormonal therapy. Resident macrophages (CD14 + CD163 + ) constituted the most frequent myeloid cell subset and expressed high levels of CD163. Elevated proportion of myeloid DC (CD14 − CD11c + ) contrasted with the paucity of plasmacytoïd DC (CD14 − CD123 + ) in testis. Myeloid-derived suppressor cells (Lin − HLA-DR − CD33 hi CD11b hi ) were not detected in the testis while constituting 0.5% of blood leucocytes. For the first time, we characterized myeloid cell subsets in human testes collected after SRS, providing a basis to assess their contribution to immune privilege. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) are key in connecting innate and adaptive immunity. Their potential in inducing specific immune responses has made them interesting targets for immunotherapeutic approaches. Our research group was the first to exploit the naturally occurring myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) in therapeutic vaccination trials against melanoma. To develop primary DC subsets as an optimal vaccine, the identification of a clinically applicable adjuvant activating both subsets is required. Although the expression of pathogen recognition receptors differs distinctly between the DC subsets, both pDCs and mDCs can respond to single-stranded RNA (ssRNA) via Toll-like receptors 7 and 8, respectively. Since ssRNA is easily degraded by RNases, we stabilized anionic RNA by complexing it with the positively charged protein protamine. This leads to the formation of protamine-RNA complexes with varying features depending on ionic content. We subsequently investigated the immunostimulatory effect of complexes that formed various salt concentrations on purified DC subsets. Both mDCs and pDCs upregulated maturation markers and produced pro-inflammatory cytokines in a dose-dependent way to the protamine-RNA complexes. This was dependent on endosomal acidification and correlated partly with the uptake of protamine-RNA complexes. Furthermore, both DC subsets induced T cell proliferation and IFN gamma secretion in a beneficial ratio to IL-10. These results indicate that protamine-RNA complexes can be used to stimulate human mDC and pDC ex vivo for use in immunotherapeutic settings. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) comprise two functionally distinct subsets: plasmacytoid DCs (pDCs) and myeloid DCs (mDCs). pDCs are specialized in rapid and massive secretion of type I interferon (IFN-I) in response to nucleic acids through Toll like receptor (TLR)-7 or TLR-9. In this report, we characterized a CD56 DC population that express typical pDC markers including CD123 and BDCA2 but produce much less IFN-I comparing with pDCs. In addition, CD56 DCs cluster together with mDCs but not pDCs by genome-wide transcriptional profiling. Accordingly, CD56 DCs functionally resemble mDCs by producing IL-12 upon TLR4 stimulation and priming naïve T cells without prior activation. These data suggest that the CD56 DCs represent a novel mDC subset mixed with some pDC features. A CD4CD56 hematological malignancy was classified as blastic plasmacytoid dendritic cell neoplasm (BPDCN) due to its expression of characteristic molecules of pDCs. However, we demonstrated that BPDCN is closer to CD56 DCs than pDCs by global gene-expression profiling. Thus, we propose that the CD4CD56 neoplasm may be a tumor counterpart of CD56 mDCs but not pDCs. [ABSTRACT FROM AUTHOR]

Morphea is one of diseases characterised by fibrosis of the skin and subcutaneous tissue. It is a chronic disease that does not shorten the life of the patient, yet significantly affects its quality. The group of factors responsible for its pathogenesis is thought to include disturbed functioning of endothelial cells as well as immune disturbances leading to chronic inflammatory conditions, accompanied by increased production of collagen and of other extracellular matrix components. Dendritic cells (DC) are a type of professional antigen-presenting cells and can be found in almost all body tissues. Individual investigations have demonstrated high numbers of plasmacytoid DC (pDC) in morphoeic skin lesions, within deeper dermal layers, around blood vessels, and around collagen fibres in subcutaneous tissue. It appears that DC has a more pronounced role in the development of inflammation and T cell activation in morphea, as compared to systemic sclerosis (SSc). Regulatory T (Treg) cells represent a subpopulation of T cells with immunosuppressive properties. Recent studies have drawn attention to the important role played by Treg in the process of autoimmunisation. Just a few studies have demonstrated a decrease in the number and activity of Treg in patients with SSc, and only such studies involve morphea. This article reviews recent studies on the role of DC and regulatory T cells in the pathogenesis of morphea. Moreover, mechanisms of phototherapy and potential therapeutic targets in the treatment of morphea are discussed in this context. [ABSTRACT FROM AUTHOR]

Abstract: Aging is associated with a progressive decline in T cell function, chronic inflammation, hyperimmunoglobulinemia, autoimmunity, poor response to vaccines, and increased susceptibility to infection as well as diseases associated with chronic inflammation. DCs in aging appear to be functionally impaired with regard to response to uptake of antigens, phagocytosis of apoptotic cells, migration, priming of CD4+ and CD8+ T cells, and production of IFN-I and IFN-III. In this review I have discussed various mechanisms, which may be responsible for impaired functions of DCs. [Copyright &y& Elsevier]

Dendritic cells (DC) in HIV-1-infected individuals are decreased and their dysfunction has been implicated in HIV-1 immunopathogenesis. The mechanism of their dysfunction remains unclear, thus we analysed the expression of membrane molecules associated with immune regulation and DC activation in myeloid (mDC) and plasmacytoid DC (pDC) in therapy-naive and highly active anti-retroviral therapy (HAART)-treated HIV-1+ patients. DC from healthy controls, untreated HIV-1+ and HAART-treated patients were assessed by flow cytometry for expression of: anergy and apoptosis inducing molecules [programmed death (PD)-1 and its ligands PD-L1 and PD-L2], inhibitory and regulatory T cell-inducing molecules [immunoglobulin-like transcript (ILT)-3 and ILT-4], interferon (IFN)-α inhibitory receptor (ILT-7) and co-stimulatory molecules (CD80, CD83, and CD86). pDC from untreated HIV-1+ patients expressed significantly lower levels of ILT-7 compared to healthy controls, while HAART-treated patients showed normal expression. pDC were also found to express moderately higher levels of PD-L1 and ILT-3 and lower levels of PD-L2 receptors in untreated patients compared to controls and HAART-treated patients. No significant changes were observed in mDC. There were no associations between the percentages and levels of expression of these molecules by pDC and viral load or CD4 T cell count. In conclusion, pDC but not mDC from HIV-1+ patients with active viraemia display higher levels of apoptosis and T regulatory-inducing molecules and may be predisposed to chronically produce IFN-α through down-regulation of ILT-7. HAART restored normal expression levels of these receptors. [ABSTRACT FROM AUTHOR]

Abstract: Background: Dendritic cells (DCs) play a pivotal role in linking the innate and adaptive immune response and have been implicated in a variety of pulmonary diseases. Currently, studies on the role of DCs are limited by difficulties in isolating DCs from the lung. Surgical lung specimens are not readily available and purification of DCs from digested lung tissue is likely to induce phenotypical and functional changes. DCs obtained from the alveolar spaces are thought to represent the local microenvironment and can be obtained using minimally invasive techniques. We developed a novel method of isolating DCs from bronchoalveolar lavage (BAL) fluid. Methods: After removal of macrophages, the remaining BAL cells were stained with a lineage mix (CD3-, CD14-, CD16-, CD19-, CD56-FITC), CD11c and HLA-DR and sorted with a FACS ARIA. DAPI was used as a dead-live marker. mDCs were low autofluorescent, lineage mix negative, CD11c+ and HLA-DR+ cells. pDCs were CD11c− but CD123+. Morphological assessment of sorted mDCs and pDCs was performed. Sorted mDCs were tested in a mixed leukocyte reaction (MLR) with naive CD4+ T cells and evaluated for T cell differentiation and cytokine production. With confocal microscopy DC–T cell interaction was assessed. Results: Using our sorting strategy, mDCs and pDCs, with a high purity upon FACS analysis of the sorted fraction, were obtained. These cells showed the morphological characteristics of DCs. Most importantly, mDCs were able to induce T cell proliferation and differentiation in a MLR, and interact with T cells as assessed by confocal microscopy. These results indicate the presence of functional DCs. Freezing and thawing of the BAL cells did not affect phenotype or T cell stimulatory capacity of the isolated DCs. Conclusion: Using a novel sorting strategy, functional mDCs can be isolated from BAL fluid, enabling a detailed study in pulmonary disease. [Copyright &y& Elsevier]

Background: Dendritic cells (DC) represent an important and integral part of the immune system and are potent initiators of inflammation. Two distinct subsets of DC have been identified: myeloid DC (MDC) and plasmacytoid DC (PDC), which differ widely in many respects. Despite the importance of the DC in the inflammatory response that occurs after severe multiple injury, there is a profound lack of information regarding the distribution and regulation of DC subtypes following multiple trauma. The main goal of this study was to assess whether the normal distribution of circulating DC subpopulations is altered during the first 5 d after multiple trauma. Patients and methods: Sixty-three patients with multiple trauma (ISS 31 ± 15 points) and 11 healthy volunteers (control group) were enrolled. Blood samples were taken on admission (D0) and daily for the following 5 d. The percentages of MDC and PDC were determined by flow cytometry. Results: A significant decline of the MDC concentration was observable on days 3 to 5 after admission in comparison to the values obtained on the day of admission. The ratio of MDC to PDC decreased significantly (3-fold, P < 0.05). This reduction correlated significantly with changes observed in the plasma concentrations of IL-10 (r = 0.5; P < 0.05). Discussion: Our data demonstrate that multiple trauma is followed by a marked change in the subpopulation composition of the DC compartment, and that these changes are inversely associated with enhanced IL-10 plasma concentrations. This imbalance in the DC compartment favoring PDC concentrations may contribute to the immunological alterations that are observed following multiple trauma. [Copyright &y& Elsevier]

Abstract: Hepatitis C virus (HCV) infection is a leading cause of chronic liver disease with over 200 million individuals infected worldwide. The vast majority of acutely infected humans develop chronic infection, which is characterized by attenuated antiviral T-cell responses. The mechanisms leading to such attenuation/suppression are poorly understood. It has been proposed that dysfunction of antigen-presenting cells (APC) may underlie the downregulation of antiviral immune responses. However, studies using bulk or in vitro-derived APC populations have resulted in conflicting reports. In this study, we evaluated the functional and immunophenotypic features of ex vivo-purified dendritic cell (DC) subsets during chronic HCV infection. We found that plasmacytoid DC (PDC) from HCV-infected patients (HCV-PDC) showed a striking deficit in IFN-α production in response to CpG stimulation. In addition, we found that myeloid DC (MDC) from these patients showed a diminished capacity to induce a mixed lymphocyte response (MLR), correlating with lower levels of HLA-DR and CD86 expression and higher IL-10 production in response to poly-IC stimulation. In contrast, HCV-PDC showed increased ability to stimulate an MLR. Of note, within the HCV-PDC preparation, we noted a distinctly expanded DC subset that expressed some markers of MDC, but showed significantly lower HLA-DR and CD86 expression, suggesting an expansion of DC at an immature/intermediate stage of differentiation. Our studies demonstrate distinct and contrasting dysfunctional features in DC subsets and underscore the importance of evaluating APC subpopulations separately. [Copyright &y& Elsevier]

Dendritic cells (DCs) are professional antigen-presenting cells that enhance and regulate both innate and acquired immune reactions. It has been reported that several viruses actively down regulate DC function to escape from host immune system. To clarify the involvement of DC in anti-hepatitis C virus (HCV) immune reactions, we compared DC function between chronic hepatitis C patients and healthy donors. Monocyte-derived DCs generated from patients were relatively immature and were impaired in allostimulatory capacity and IL-12 p70 production when compared to that from donors. In addition, MDC and PDC in HCV-infected patients were reduced in number and impaired in their ability to promote Th1 polarization. These results demonstrate that DCs are numerically and functionally impaired in HCV-infected patients, which is critically involved in the pathogenesis and persistence of HCV infection. [ABSTRACT FROM AUTHOR]

Because of the potent graft-versus-tumor (GVT) effect, allogeneic stem cell transplantation (alloSCT) can be a curative therapy for hematological malignancies. However, relapse remains the most frequent cause of treatment failure, illustrating the necessity for development of adjuvant post-transplant therapies to boost GVT immunity. Dendritic cell (DC) vaccination is a promising strategy in this respect, in particular, where distinct biologic functions of naturally occurring DC subsets, i.e. myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), are harnessed. However, it is challenging to obtain high enough numbers of primary DC subsets from blood for immunotherapy due to their low frequencies. Therefore, we present here anex vivoGMP-compliant cell culture protocol for generating different DC subsets from CD34+hematopoietic stem and progenitor cells (HSPCs) of alloSCT donor origin. High numbers of BDCA1+mDCs and pDCs could be generated, sufficient for multiple vaccination cycles. These HSPC-derived DC subsets were highly potent in inducing antitumor immune responsesin vitro. Notably, HSPC-derived BDCA1+mDCs were superior in eliciting T cell responses. They efficiently primed naïve T cells and robustly expanded patient-derived minor histocompatibility antigen (MiHA)-specific T cells. Though the HSPC-pDCs also efficiently induced T cell responses, they exhibited superior capacity in activating NK cells. pDC-primed NK cells highly upregulated TRAIL and possessed strong cytolytic capacity against tumor cells. Collectively, these findings indicate that HSPC-derived DC vaccines, comprising both mDCs and pDCs, may possess superior potential to boost antitumor immunity post alloSCT, due to their exceptional T cell and NK cell stimulatory capacity. [ABSTRACT FROM AUTHOR]