Early antitumor activity of oral Langerhans cells is compromised by a carcinogen

Early diagnosis of oral squamous cell carcinoma (OSCC) remains an unmet clinical need. Therefore, elucidating the initial events of OSCC preceding tumor development could benefit OSCC prognosis. Here, we define the Langerhans cells (LCs) of the tongue and demonstrate that LCs protect the epithelium from carcinogen-induced OSCC by rapidly priming αβT cells capable of eliminating γH2AX+ epithelial cells, whereas γδT and natural killer cells are dispensable. The carcinogen, however, dysregulates the epithelial resident mononuclear phagocytes, reducing LC frequencies, while dendritic cells (DCs), macrophages, and plasmacytoid DCs (pDCs) populate the epithelium. Single-cell RNA-sequencing analysis indicates that these newly differentiated cells display an immunosuppressive phenotype accompanied by an expansion of T regulatory (Treg) cells. Accumulation of the Treg cells was regulated, in part, by pDCs and precedes the formation of visible tumors. This suggests LCs play an early protective role during OSCC, yet the capacity of the carcinogen to dysregulate the differentiation of mononuclear phagocytes facilitates oral carcinogenesis.

Transition from cMyc to L-Myc during dendritic cell development coordinated by rising levels of IRF8

During dendritic cell (DC) development, Myc expression in progenitors is replaced by Mycl in mature DCs, but when and how this transition occurs is unknown. We evaluated DC development using reporters for MYC, MYCL, and cell cycle proteins Geminin and CDT1 in wild-type and various mutant mice. For classical type 1 dendritic cells (cDC1s) and plasmacytoid DCs (pDCs), the transition occurred upon their initial specification from common dendritic cell progenitors (CDPs) or common lymphoid progenitors (CLPs), respectively. This transition required high levels of IRF8 and interaction with PU.1, suggesting the use of EICEs within Mycl enhancers. In pDCs, maximal MYCL induction also required the +41kb Irf8 enhancer that controls pDC IRF8 expression. IRF8 also contributed to repression of MYC. While MYC is expressed only in rapidly dividing DC progenitors, MYCL is most highly expressed in DCs that have exited the cell cycle. Thus, IRF8 levels coordinate the Myc-Mycl transition during DC development.

Quantification of dendritic cell subsets in human thymus tissues of various ages

Background Dendritic cells (DCs) in the thymus are involved in central tolerance formation, but they also have other functions in the thymus, such as pathogen recognition. The density changes of human thymic DCs have been hardly investigated. In this study, human thymus samples of various ages were collected for tissue sectioning and staining. The thymic cortex and medulla area as well as the densities of various subsets of thymic DCs were calculated. Results All common DC subsets were found in the human thymus of various ages. Most DCs had accumulated in the human thymic epithelial space, especially the medulla. We also found that the human thymic cortex had atrophied relatively faster than the medulla, which led to a gradual increase of the area ratio of the medulla to cortex with the increase of age. The densities of DC subsets in the human thymus showed various changes with increasing age, which contributed to the composition changes of DC subsets. The density of plasmacytoid DCs (pDCs) in the human thymus had increased gradually with aging, which suggested that pDCs plays another essential role in the thymus in addition to central tolerance. Conclusions Inconsistent with the shrinking of the epithelial space in the thymus, the densities of DC subsets in the epithelial space of the thymus are maintained at a constant level with aging to preserve highly efficient autoreactive thymocyte screening. An increasing density of the thymic pDCs with aging implies an extra function of DCs in the thymus beyond central tolerance.

EFFECT OF DNA CONSTRUCTIONS ELECTROPORATION ON DENDRITIC CELLS

Today transfection of mammalian cell with DNA or RNA construction is the only method for delivering programmed information into the cell nucleus. Electroporation is most commonly used method of transfection in experiments with dendritic cell. The aim of electroporation is to permeabilize the membrane by passing electric impulse through the cell. Due to the increase permeability of the membrane chance DNA or RNA construction getting inside into the cell is increased, wherein survival of the cells is decreased.In the study male mice C57Bl/6 line 2-4 months old were used. From femur bones was isolated 20 × 106 bone marrow cells, which were cultured in 20 mL of complete RPMI-1640 for 7 days. To generate dendritic cells from BM cells, 100 ng/mL of rmFlt3-L was added to culture media at day 0. After 7 days of cultivation, the cell cultures were electroporated with control noncoding plasmids p5 (EP P5) or pmaxCCR9 encoding mouse chemokine receptor CCR9 (EP CCR9). The controls were cell cultures electroporated without any plasmids (mock EP) and cell cultures without electroporation (none EP). 5 × 105 cells were electroporated and resting for 10 minutes. After 10 minutes, cells were harvested and seeded into 24-well plates in 1 mL of culture medium and conditioning medium (1:1). Then, 50 ng/mL of Flt3-L was added to each well. The next day, transfected cells were collected and used for flow cytometry, qRT-PCR analysis.It was found that after electroporation in the groups mock EP, EP P5, EP CCR9 relative amount of live CD11c+ dendritic cells was significantly less than in the non EP group. Moreover, in the EP P5 and EP CCR9 groups the frequency of live CD11c+ dendritic cells was significantly less than in the mock EP group. Expression of the CD86 marker in the EP P5 and EP CCR9 groups was significantly higher than in the non EP and mock EP groups. Expression of the I-AB(MHCII) in the EP CCR9 group on cDC2s was significantly higher than in the non EP group. On plasmacytoid DCs (pDCs) and conventional type 2 DCs (cDC2s) in the EP CCR9 group expression of CCR9 was significantly higher than in the non EP group. Therefore, in this study, we demonstrated the effectiveness of electroporation, accompanied by the decrease in the survival rate and maturation of DCs.

SARS-CoV-2 Impairs Dendritic Cells and Regulates DC-SIGN Gene Expression in Tissues

The current spreading coronavirus SARS-CoV-2 is highly infectious and pathogenic. In this study, we screened the gene expression of three host receptors (ACE2, DC-SIGN and L-SIGN) of SARS coronaviruses and dendritic cells (DCs) status in bulk and single cell transcriptomic datasets of upper airway, lung or blood of COVID-19 patients and healthy controls. In COVID-19 patients, DC-SIGN gene expression was interestingly decreased in lung DCs but increased in blood DCs. Within DCs, conventional DCs (cDCs) were depleted while plasmacytoid DCs (pDCs) were augmented in the lungs of mild COVID-19. In severe cases, we identified augmented types of immature DCs (CD22+ or ANXA1+ DCs) with MHCII downregulation. In this study, our observation indicates that DCs in severe cases stimulate innate immune responses but fail to specifically present SARS-CoV-2. It provides insights into the profound modulation of DC function in severe COVID-19.

Tocilizumab Induces IL-10-Mediated Immune Tolerance in Invasive Candidiasis

The existence of a hyperinflammatory state has been observed in patients with invasive fungal infections (IFI). It is being postulated whether morbidity from IFI may, in part, be a consequence of an unnecessarily prolonged or exaggerated proinflammatory immune response including interleukin 6 (IL-6) post-infection, in a host with dysregulated or compromised immunity. This, in turn, induces collateral host injury at the tissue and organ level, leading to adverse outcomes. Tocilizumab has become widely used as an immunomodulator in the treatment of inflammatory conditions. Here, we evaluated the use of tocilizumab to curb post-infective inflammatory flare in the setting of an in-vivo mouse model for invasive candidiasis. Following Candida infection, the tocilizumab-treated mice showed improved short-term survival compared with the saline-treated control mice. There was a reduced inflammatory response mounted by the host, coupled with reduced IL-6 but increased IL-10 levels. TNF-α and IFN-γ responses were not affected. Tocilizumab facilitated immune tolerance by selectively inducing IL-10, producing CD8α+ conventional dendritic cells (DCs) and peripheral T-regulatory cells, over CD11b+ conventional DCs and plasmacytoid DCs. We demonstrate here the sequelae from immunomodulatory manipulation and the basis whereby the use of monoclonal antibodies may be further explored in IFI.

Swine Dendritic Cell Response to Porcine Reproductive and Respiratory Syndrome Virus: An Update

Dendritic cells (DCs) are the most potent antigen-presenting cells, unique to initiate and coordinate the adaptive immune response. In pigs, conventional DCs (cDCs), plasmacytoid DCs (pDCs), and monocyte-derived DCs (moDCs) have been described in blood and tissues. Different pathogens, such as viruses, could infect these cells, and in some cases, compromise their response. The understanding of the interaction between DCs and viruses is critical to comprehend viral immunopathological responses. Porcine reproductive and respiratory syndrome virus (PRRSV) is the most important respiratory pathogen in the global pig population. Different reports support the notion that PRRSV modulates pig immune response in addition to their genetic and antigenic variability. The interaction of PRRSV with DCs is a mostly unexplored area with conflicting results and lots of uncertainties. Among the scarce certainties, cDCs and pDCs are refractory to PRRSV infection in contrast to moDCs. Additionally, response of DCs to PRRSV can be different depending on the type of DCs and maybe is related to the virulence of the viral isolate. The precise impact of this virus-DC interaction upon the development of the specific immune response is not fully elucidated. The present review briefly summarizes and discusses the previous studies on the interaction of in vitro derived bone marrow (bm)- and moDCs, and in vivo isolated cDCs, pDCs, and moDCs with PRRSV1 and 2.

Regulatory Dendritic Cells Induced by Bendamustine Are Associated With Enhanced Flt3 Expression and Alloreactive T-Cell Death

The growth factor Flt3 ligand (Flt3L) is central to dendritic cell (DC) homeostasis and development, controlling survival and expansion by binding to Flt3 receptor tyrosine kinase on the surface of DCs. In the context of hematopoietic cell transplantation, Flt3L has been found to suppress graft-versus-host disease (GvHD), specifically via host DCs. We previously reported that the pre-transplant conditioning regimen consisting of bendamustine (BEN) and total body irradiation (TBI) results in significantly reduced GvHD compared to cyclophosphamide (CY)+TBI. Pre-transplant BEN+TBI conditioning was also associated with greater Flt3 expression among host DCs and an accumulation of pre-cDC1s. Here, we demonstrate that exposure to BEN increases Flt3 expression on both murine bone marrow-derived DCs (BMDCs) and human monocyte-derived DCs (moDCs). BEN favors development of murine plasmacytoid DCs, pre-cDC1s, and cDC2s. While humans do not have an identifiable equivalent to murine pre-cDC1s, exposure to BEN resulted in decreased plasmacytoid DCs and increased cDC2s. BEN exposure and heightened Flt3 signaling are associated with a distinct regulatory phenotype, with increased PD-L1 expression and decreased ICOS-L expression. BMDCs exposed to BEN exhibit diminished pro-inflammatory cytokine response to LPS and induce robust proliferation of alloreactive T-cells. These proliferative alloreactive T-cells expressed greater levels of PD-1 and underwent increased programmed cell death as the concentration of BEN exposure increased. Alloreactive CD4+ T-cell death may be attributable to pre-cDC1s and provides a potential mechanism by which BEN+TBI conditioning limits GvHD and yields T-cells tolerant to host antigen.

Quantify each Dendritic Cell Subsets along with Normal Thymus Tissues in Different Ages

BackgroundDendritic cells (DCs) in the thymus are involved in central tolerance formation, but they also play other roles in the thymus. In this study, thymuses of different ages were collected for observation after tissue sectioning and staining. The area of cortex and medulla parts of the thymus in the sections and the density of different subsets of DCs in the thymus were also calculated. ResultsWe found that, along with the increasing age, the thymic cortex atrophies faster, leading to a gradual rise in the medullary's surface area ratio to that of the cortex with an increase in age. The medullary's surface area ratio to cortex can be used as an indirect reference to reflect the thymus hyperplasia. The density of DCs in the thymus showed different changes with the increasing age, and the density of plasmacytoid DCs (pDCs) in the thymus gradually increased with aging, suggesting that pDCs may play an essential role in the thymus in addition to central tolerance.ConclusionsThese findings complement our knowledge about the DCs’ subsets in the thymus along with physical ageing and help us understand the full function of DCs in the thymus beyond central tolerance.

AB0023 DENDRITIC CELLS AS A PROMINENT MARKERS OF AUTOIMMUNE DISEASES

Background:Dendritic cells (DCs) are known to contribute to the pathogenesis of different autoimmune diseases. It is clear nowadays the role of DCs in rheumatoid arthritis (RA) but not well investigated in Axial spondylitis (AxSpA). DCs are a heterogeneous population and can be divided into groups: myeloid (mDCs) and plasmacytoid (pDCs). DCs can induce both immune response and tolerance.Objectives:To investigate the subpopulations of peripheral blood myeloid and plasmacytoid DCs in patients with early stage of RA (duration of illness up to 12 months) and AS.Methods:The study include sixty five patients with early forms of diseases including 55 patients with RA and 10 patients with AxSpA. Diagnosis RA was established according ACR/EULAR criteria (2010). Diagnosis AxSpA was established according ASAS criteria. All patients received conventional synthetic DMARDs. Thirty patients with osteoarthritis (OA) used as a control group. Analysis of the content of the B-lymphocytes, myeloid and plasmacytoid DCs was carried out by flow cytometry. B-lymphocytes, subtypes of peripheral blood DCs were characterized by the following phenotypes: myeloid DCs (CD3-CD14-CD19-HLA-DR + CD11c + CD123-), plasmacytoid DCs (CD3-CD14-CD19-HLA-DR + CD11c-CD123 +), B-lymphocytes (CD19 +). Analyses were performed before treatment and after 3 and 6 months.Results:Patients with early RA are characterized by significant evaluation of the population of myeloid DCs in comparison of patients with osteoarthritis (25.3% vs 21.5, p=0.005). Furthermore, the difference was found in the number of cells with the phenotype B-lymphocytes: 5.7% vs 3.1%, p = 0.0007). No significant differences were observed in the number of plasmocytoid DCs. After 3 and 6 month of observation we detected reducing amount of myeloid DCs 26.7% vs 20.1% vs 16.4% respectively. Disease activity according to DAS28 droped to low (4.32 to3.06, p=0.03). Patients with AxSpA are characterized a lower mDCs levels in compared with RA (19.3% vs 26.7, p=0.07). After 6 month of investigation we detected decreasing mDCs (19.3% to 14.2%, p=0.05). The percent of pDCs were constant and did not differ from the level of healthy donors.Conclusion:The data obtained indicate that early form of rheumatic diseases namely rheumatoid arthritis and axial spondylitis have the common features such as the dominance of mDCs and their decreasing in reduction of activity of disease.Disclosure of Interests:None declared