Avoiding horror autotoxicus: the importance of dendritic cells in peripheral T cell tolerance

Striking a balance: new perspectives on homeostatic dendritic cell maturation

Dendritic cells (DCs) are crucial gatekeepers of the balance between immunity and tolerance. They exist in two functional states, immature or mature, that refer to an information-sensing versus an information-transmitting state, respectively. Historically, the term DC maturation was used to describe the acquisition of immunostimulatory capacity by DCs following their triggering by pathogens or tissue damage signals. As such, immature DCs were proposed to mediate tolerance, whereas mature DCs were associated with the induction of protective T cell immunity. Later studies have challenged this view and unequivocally demonstrated that two distinct modes of DC maturation exist, homeostatic and immunogenic DC maturation, each with a distinct functional outcome. Therefore, the mere expression of maturation markers cannot be used to predict immunogenicity. How DCs become activated in homeostatic conditions and maintain tolerance remains an area of intense debate. Several recent studies have shed light on the signals driving the homeostatic maturation programme, especially in the conventional type 1 DC (cDC1) compartment. Here, we highlight our growing understanding of homeostatic DC maturation and the relevance of this process for immune tolerance.

Allograft tolerance after adult living donor liver transplantation: a case-control study

BACKGROUND

To investigate the incidence and potential predictors of immune tolerance among adult living donor liver transplant (LDLT) recipients.

METHODS

This case-control study included adult recipients who underwent LDLT between May 2004 and January 2018, with at least a 5-year follow-up after LDLT. We divided the study recipients into two groups: Group 1 (Tolerance Group) included recipients who achieved operational or prope tolerance for at least one year; Group 2 (Control Group) included recipients who did not achieve tolerance. We used logistic regression analysis to study the potential predictors of tolerance after LDLT.

RESULTS

We included 368 recipients, 275 (74.7%) in Group 1 and 93 (25.3%) in Group 2. Operational tolerance occurred in 13/275 (4.7%) recipients and prope tolerance in 262/275 (95.3%) recipients. Age was significantly higher in Group 1. The median time for tolerance among the study recipients was 60 months (36-168). During follow-up, Group 1 showed lower serum levels of bilirubin, liver enzymes, alkaline phosphatase, and gamma-glutamyl transferase. Group 1 had a lower incidence of acute cellular rejection (ACR), recurrent viral hepatitis, and biliary complications. Logistic regression identified preoperative MELD, indication for LDLT, ACR, recurrent viral hepatitis, and biliary complications as significant predictors for allograft tolerance after LDLT.

CONCLUSION

Allograft tolerance occurred in 74.7% of this cohort. We suggest that the MELD score, indication for LT, ACR, recurrent viral hepatitis, and biliary complications are predictors of allograft tolerance after LDLT.

The effect of microbial metabolites from colonic protein fermentation on bacteria-induced cytokine production in dendritic cells

Compared to the well-defined immune-modulating effect of butyrate, the understanding of the effect of other protein fermentation metabolites is limited. This study aimed to investigate the impact of protein-derived metabolites (valerate, branched-chain fatty acids, ammonium, phenol, p-Cresol, indole, and hydrogen sulfide) on cytokine production in murine bone marrow-derived dendritic cells (BMDCs) stimulated with lipopolysaccharides (LPS), Lactobacillus acidophilus NCFM, or Staphylococcus aureus USA300. Some of the metabolites, but not the short-chain fatty acids (SCFAs), strongly affected cell viability. After short-term treatment and depending on the microbial stimulus, SCFAs affected the cytokine profile similarly but weaker than butyrate, as reflected by inhibition of IL-12p70 and IL-10 but enhanced IL-23 (LPS and S. aureus USA300) and IL-1β production. Compared to butyrate, valerate exhibited a weaker and slower effect on cytokine expression. Two-day treatment with valerate and butyrate resulted in similar effects, that is, LPS-induced IL-12 abrogation and IL-10 enhancement, increased aryl hydrocarbon receptor (Ahr) expression, and after LPS stimulation, increased expression of dual specificity phosphatase 1 (Dusp1). In conclusion, SCFAs exhibited low toxicity and modulated microbially stimulated BMDCs. Valerate and butyrate showed the strongest effect, which was dependent on the specific microbial stimulation and the course of the SCFA treatment. Our work adds knowledge regarding the role of protein-derived metabolites from gut bacterial fermentation on the immune system.

Dysfunction of dendritic cells in tumor microenvironment and immunotherapy

Dendritic cells (DCs) comprise diverse cell populations that play critical roles in antigen presentation and triggering immune responses in the body. However, several factors impair the immune function of DCs and may promote immune evasion in cancer. Understanding the mechanism of DC dysfunction and the diverse functions of heterogeneous DCs in the tumor microenvironment (TME) is critical for designing effective strategies for cancer immunotherapy. Clinical applications targeting DCs summarized in this report aim to improve immune infiltration and enhance the biological function of DCs to modulate the TME to prevent cancer cells from evading the immune system. Herein, factors in the TME that induce DC dysfunction, such as cytokines, hypoxic environment, tumor exosomes and metabolites, and co-inhibitory molecules, have been described. Furthermore, several key signaling pathways involved in DC dysfunction and signal-relevant drugs evaluated in clinical trials were identified. Finally, this review provides an overview of current clinical immunotherapies targeting DCs, especially therapies with proven clinical outcomes, and explores future developments in DC immunotherapies.

Optimization of Interleukin-10 incorporation for dendritic cells embedded in Poly(ethylene glycol) hydrogels

Translational research in biomaterials and immunoengineering is leading to the development of novel advanced therapeutics to treat diseases such as cancer, autoimmunity, and viral infections. Dendritic cells (DCs) are at the center of these therapeutics given that they bridge innate and adaptive immunity. The biomaterial system developed herein uses a hydrogel carrier to deliver immunomodulatory DCs for amelioration of autoimmunity. This biomaterial vehicle is comprised of a poly (ethylene glycol)-4 arm maleimide (PEG-4MAL) hydrogels, conjugated with the immunosuppressive cytokine, interleukin-10, IL-10, and cross-linked with a collagenase-degradable peptide sequence for the injectable delivery of immunosuppressive DCs to an anatomical disease-relevant site of the cervical lymph nodes, for intended application to treat multiple sclerosis. The amount of IL-10 incorporated in the hydrogel was optimized to be 500 ng in vitro, based on immunological endpoints. At this concentration, DCs exhibited the best viability, most immunosuppressive phenotype, and protection against proinflammatory insult as compared with hydrogel-incorporated DCs with lower IL-10 loading amounts. Additionally, the effect of the degradability of the PEG-4MAL hydrogel on the release rate of incorporated IL-10 was assessed by varying the ratio of degradable peptides: VPM (degradable) and DTT (nondegradable) and measuring the IL-10 release rates. This IL-10-conjugated hydrogel delivery system for immunosuppressive DCs is set to be assessed for in vivo functionality as the immunosuppressive cytokine provides a tolerogenic environment that keeps DCs in their immature phenotype, which consequently enhances cell viability and optimizes the system's immunomodulatory functionality.

Activation of Wnt/β-catenin signal induces DCs to differentiate into immune tolerant regDCs in septic mice

BACKGROUND

Sepsis is a common complication among patients in intensive care units, and has a high mortality rate, with no effective therapies to date. As immunosuppression has become the research focus of sepsis, the regulatory role of dendritic cells (DCs) in the immune response to sepsis has received attention.

OBJECTIVE

To investigate the role of the Wnt/β-catenin signaling pathway in inducing the differentiation of splenic DCs in mice with sepsis caused by cecal ligation and puncture (CLP).

METHODS

C57bl/6 mice were randomly divided into three groups, namely the sham, 24 h post-CLP, and 72 h post-CLP groups. Levels of regulatory T cells (Tregs) among splenic mononuclear cells, suppressor T cells (TSs), and surface markers, such as major histocompatibility complex class II (MHC-II), co-stimulatory molecules (CD80 and CD86), negative co-stimulatory molecule death-ligand 1 (PD-L1), CC chemokine receptor-5 (CCR5), and CC chemokine receptor-7 (CCR7), were analyzed via flow cytometry for each group of mice post-surgery. CD11c+ DCs were purified from the splenic mononuclear cells of each group, and the expression of β-catenin, Wnt5a, and Wnt3a was detected using RT-PCR and western blotting.Each group of DCs was incubated with LPS-containing culture solution, and the supernatant of the culture solution was collected after 24 hours to detect the level of Tumor necrosis factor-α(TNF-α), interleukin (IL)-6, IL-12, and IL-10.

RESULTS

Compared with that in the sham group, the expression of β-catenin, Wnt5a, and Wnt3a in splenic DCs of the other two groups of mice increased with prolonged CLP exposure (P<0.05). Meanwhile, the proportion of Tregs and TSs increased in the mouse spleens after CLP, and levels of DC surface molecules, such as CCR5, CCR7, CD80, CD86, and MHC-II, decreased to different degrees, whereas those of PD-L1 increased. These results suggested that DCs differentiate towards regulatory DCs (regDCs) after CLP in mice. The results of ELISA showed that the longer the exposure time after CLP, the lower the ability of DCs to secrete TNF-α and IL-12, but the higher the level of IL-10 and IL-6.

CONCLUSION

The Wnt/β-catenin signaling pathway activates and induces regDCs differentiation in the splenic DCs of mice with sepsis and participates in the regulation of immune tolerance in the organism.

Unbiasedly decoding the tumor microenvironment with single-cell multiomics analysis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a poor prognosis and limited therapeutic options. Research on the tumor microenvironment (TME) of PDAC has propelled the development of immunotherapeutic and targeted therapeutic strategies with a promising future. The emergence of single-cell sequencing and mass spectrometry technologies, coupled with spatial omics, has collectively revealed the heterogeneity of the TME from a multiomics perspective, outlined the development trajectories of cell lineages, and revealed important functions of previously underrated myeloid cells and tumor stroma cells. Concurrently, these findings necessitated more refined annotations of biological functions at the cell cluster or single-cell level. Precise identification of all cell clusters is urgently needed to determine whether they have been investigated adequately and to identify target cell clusters with antitumor potential, design compatible treatment strategies, and determine treatment resistance. Here, we summarize recent research on the PDAC TME at the single-cell multiomics level, with an unbiased focus on the functions and potential classification bases of every cellular component within the TME, and look forward to the prospects of integrating single-cell multiomics data and retrospectively reusing bulk sequencing data, hoping to provide new insights into the PDAC TME.

Immunogenic cell death in cancer: targeting necroptosis to induce antitumour immunity

Most metastatic cancers remain incurable due to the emergence of apoptosis-resistant clones, fuelled by intratumour heterogeneity and tumour evolution. To improve treatment, therapies should not only kill cancer cells but also activate the immune system against the tumour to eliminate any residual cancer cells that survive treatment. While current cancer therapies rely heavily on apoptosis - a largely immunologically silent form of cell death - there is growing interest in harnessing immunogenic forms of cell death such as necroptosis. Unlike apoptosis, necroptosis generates second messengers that act on immune cells in the tumour microenvironment, alerting them of danger. This lytic form of cell death optimizes the provision of antigens and adjuvanticity for immune cells, potentially boosting anticancer treatment approaches by combining cellular suicide and immune response approaches. In this Review, we discuss the mechanisms of necroptosis and how it activates antigen-presenting cells, drives cross-priming of CD8+ T cells and induces antitumour immune responses. We also examine the opportunities and potential drawbacks of such strategies for exposing cancer cells to immunological attacks.

Engineering Antigen-Specific Tolerance to an Artificial Protein Hydrogel

Artificial protein hydrogels are an emerging class of biomaterials with numerous prospective applications in tissue engineering and regenerative medicine. These materials are likely to be immunogenic due to their frequent incorporation of novel amino acid sequence domains, which often serve a functional role within the material itself. We engineered injectable "self" and "nonself" artificial protein hydrogels, which were predicted to have divergent immune outcomes in vivo on the basis of their primary amino acid sequence. Following implantation in mouse, the nonself gels raised significantly higher antigel antibody titers than the corresponding self gels. Prophylactic administration of a fusion antibody targeting the nonself hydrogel epitopes to DEC-205, an endocytic receptor involved in Treg induction, fully suppressed the elevated antibody titer against the nonself gels. These results suggest that the clinical immune response to artificial protein biomaterials, including those that contain highly antigenic sequence domains, can be tuned through the induction of antigen-specific tolerance.

T-cell immunity against senescence: potential role and perspectives

The development of age-associated diseases is related to the accumulation of senescent cells in the body. These are old non-functional cells with impaired metabolism, which are unable to divide. Such cells are also resistant to programmed cell death and prone to spontaneous production of some inflammatory factors. The accumulation of senescent cells is related to the age-associated dysfunction of organs and tissues as well as chronic inflammation that enhances with age. In the young organism, senescent cells are removed with the innate immunity system. However, the efficiency of this process decreases with age. Nowadays, more and more evidences are accumulating to support the involvement of specific immunity and T-lymphocytes in the fight against senescent cells. It has great physiological importance since the efficient elimination of senescent cells requires a high diversity of antigen-recognizing receptors to cover the entire spectrum of senescent-associated antigens with high precision and specificity. Developing the approaches of T-cell immunity stimulation to generate or amplify a physiological immune response against senescent cells can provide new perspectives to extend active longevity. In this mini-review, the authors summarize the current understanding of the role of T-cell immunity in the fight against senescent cells and discuss the prospects of stimulating adaptive immunity for combating the accumulation of senescent cells that occurs with age.

Reduced interleukin-18 secretion by human monocytic cells in response to infections with hyper-virulent Streptococcus pyogenes

BACKGROUND

Streptococcus pyogenes (group A streptococcus, GAS) causes a variety of diseases ranging from mild superficial infections of the throat and skin to severe invasive infections, such as necrotizing soft tissue infections (NSTIs). Tissue passage of GAS often results in mutations within the genes encoding for control of virulence (Cov)R/S two component system leading to a hyper-virulent phenotype. Dendritic cells (DCs) are innate immune sentinels specialized in antigen uptake and subsequent T cell priming. This study aimed to analyze cytokine release by DCs and other cells of monocytic origin in response to wild-type and natural covR/S mutant infections.

METHODS

Human primary monocyte-derived (mo)DCs were used. DC maturation and release of pro-inflammatory cytokines in response to infections with wild-type and covR/S mutants were assessed via flow cytometry. Global proteome changes were assessed via mass spectrometry. As a proof-of-principle, cytokine release by human primary monocytes and macrophages was determined.

RESULTS

In vitro infections of moDCs and other monocytic cells with natural GAS covR/S mutants resulted in reduced secretion of IL-8 and IL-18 as compared to wild-type infections. In contrast, moDC maturation remained unaffected. Inhibition of caspase-8 restored secretion of both molecules. Knock-out of streptolysin O in GAS strain with unaffected CovR/S even further elevated the IL-18 secretion by moDCs. Of 67 fully sequenced NSTI GAS isolates, 28 harbored mutations resulting in dysfunctional CovR/S. However, analyses of plasma IL-8 and IL-18 levels did not correlate with presence or absence of such mutations.

CONCLUSIONS

Our data demonstrate that strains, which harbor covR/S mutations, interfere with IL-18 and IL-8 responses in monocytic cells by utilizing the caspase-8 axis. Future experiments aim to identify the underlying mechanism and consequences for NSTI patients.

Decoding immunogenic cell death from a dendritic cell perspective

Dendritic cells (DCs) are myeloid cells bridging the innate and adaptive immune system. By cross-presenting tumor-associated antigens (TAAs) liberated upon spontaneous or therapy-induced tumor cell death to T cells, DCs occupy a pivotal position in the cancer immunity cycle. Over the last decades, the mechanisms linking cancer cell death to DC maturation, have been the focus of intense research. Growing evidence supports the concept that the mere transfer of TAAs during the process of cell death is insufficient to drive immunogenic DC maturation unless this process is coupled with the release of immunomodulatory signals by dying cancer cells. Malignant cells succumbing to a regulated cell death variant called immunogenic cell death (ICD), foster a proficient interface with DCs, enabling their immunogenic maturation and engagement of adaptive immunity against cancer. This property relies on the ability of ICD to exhibit pathogen-mimicry hallmarks and orchestrate the emission of a spectrum of constitutively present or de novo-induced danger signals, collectively known as damage-associated molecular patterns (DAMPs). In this review, we discuss how DCs perceive and decode danger signals emanating from malignant cells undergoing ICD and provide an outlook of the major signaling and functional consequences of this interaction for DCs and antitumor immunity.

FLT3L-dependent dendritic cells control tumor immunity by modulating Treg and NK cell homeostasis

FLT3-L-dependent classical dendritic cells (cDCs) recruit anti-tumor and tumor-protecting lymphocytes. We evaluate cancer growth in mice with low, normal, or high levels of cDCs. Paradoxically, both low or high numbers of cDCs improve survival in mice with melanoma. In low cDC context, tumors are restrained by the adaptive immune system through influx of effector T cells and depletion of Tregs and NK cells. High cDC numbers favor the innate anti-tumor response, with massive recruitment of activated NK cells, despite high Treg infiltration. Anti CTLA-4 but not anti PD-1 therapy synergizes with FLT3-L therapy in the cDCHi but not in the cDCLo context. A combination of cDC boost and Treg depletion dramatically improves survival of tumor-bearing mice. Transcriptomic data confirm the paradoxical effect of cDC levels on survival in several human tumor types. cDCHi-TregLo state in such patients predicts best survival. Modulating cDC numbers via FLT3 signaling may have therapeutic potential in human cancer.

Introducing Molecular Chaperones into the Causality and Prospective Management of Autoimmune Hepatitis

Molecular chaperones influence the immunogenicity of peptides and the activation of effector T cells, and their pathogenic roles in autoimmune hepatitis are unclear. Heat shock proteins are pivotal in the processing and presentation of peptides that activate CD8+ T cells. They can also induce regulatory B and T cells and promote immune tolerance. Tapasin and the transporter associated with antigen processing-binding protein influence the editing and loading of high-affinity peptides for presentation by class I molecules of the major histocompatibility complex. Their over-expression could enhance the autoimmune response, and their deficiency could weaken it. The lysosome-associated membrane protein-2a isoform in conjunction with heat shock cognate 70 supports the importation of cytosolic proteins into lysosomes. Chaperone-mediated autophagy can then process the peptides for activation of CD4+ T cells. Over-expression of autophagy in T cells may also eliminate negative regulators of their activity. The human leukocyte antigen B-associated transcript three facilitates the expression of class II peptide receptors, inhibits T cell apoptosis, prevents T cell exhaustion, and sustains the immune response. Immunization with heat shock proteins has induced immune tolerance in experimental models and humans with autoimmune disease by inducing regulatory T cells. Therapeutic manipulation of other molecular chaperones may promote T cell exhaustion and induce tolerogenic dendritic cells. In conclusion, molecular chaperones constitute an under-evaluated family of ancillary proteins that could affect the occurrence, severity, and outcome of autoimmune hepatitis. Clarification of their contributions to the immune mechanisms and clinical activity of autoimmune hepatitis could have therapeutic implications.

Transcriptional regulation of dendritic cell development and function

Dendritic cells (DCs) are sentinel immune cells that form a critical bridge linking the innate and adaptive immune systems. Extensive research addressing the cellular origin and heterogeneity of the DC network has revealed the essential role played by the spatiotemporal activity of key transcription factors. In response to environmental signals DC mature but it is only following the sensing of environmental signals that DC can induce an antigen specific T cell response. Thus, whilst the coordinate action of transcription factors governs DC differentiation, sensing of environmental signals by DC is instrumental in shaping their functional properties. In this review, we provide an overview that focuses on recent advances in understanding the transcriptional networks that regulate the development of the reported DC subsets, shedding light on the function of different DC subsets. Specifically, we discuss the emerging knowledge on the heterogeneity of cDC2s, the ontogeny of pDCs, and the newly described DC subset, DC3. Additionally, we examine critical transcription factors such as IRF8, PU.1, and E2-2 and their regulatory mechanisms and downstream targets. We highlight the complex interplay between these transcription factors, which shape the DC transcriptome and influence their function in response to environmental stimuli. The information presented in this review provides essential insights into the regulation of DC development and function, which might have implications for developing novel therapeutic strategies for immune-related diseases.

Signaling pathways involved in the biological functions of dendritic cells and their implications for disease treatment

The ability of dendritic cells (DCs) to initiate and regulate adaptive immune responses is fundamental for maintaining immune homeostasis upon exposure to self or foreign antigens. The immune regulatory function of DCs is strictly controlled by their distribution as well as by cytokines, chemokines, and transcriptional programming. These factors work in conjunction to determine whether DCs exert an immunosuppressive or immune-activating function. Therefore, understanding the molecular signals involved in DC-dependent immunoregulation is crucial in providing insight into the generation of organismal immunity and revealing potential clinical applications of DCs. Considering the many breakthroughs in DC research in recent years, in this review we focused on three basic lines of research directly related to the biological functions of DCs and summarized new immunotherapeutic strategies involving DCs. First, we reviewed recent findings on DC subsets and identified lineage-restricted transcription factors that guide the development of different DC subsets. Second, we discussed the recognition and processing of antigens by DCs through pattern recognition receptors, endogenous/exogenous pathways, and the presentation of antigens through peptide/major histocompatibility complexes. Third, we reviewed how interactions between DCs and T cells coordinate immune homeostasis in vivo via multiple pathways. Finally, we summarized the application of DC-based immunotherapy for autoimmune diseases and tumors and highlighted potential research prospects for immunotherapy that targets DCs. This review provides a useful resource to better understand the immunomodulatory signals involved in different subsets of DCs and the manipulation of these immune signals can facilitate DC-based immunotherapy.

Immunomodulatory Mechanism and Potential Application of Dental Pulp-Derived Stem Cells in Immune-Mediated Diseases

Dental pulp stem cells (DPSCs) are mesenchymal stem cells (MSCs) derived from dental pulp tissue, which have high self-renewal ability and multi-lineage differentiation potential. With the discovery of the immunoregulatory ability of stem cells, DPSCs have attracted much attention because they have similar or even better immunomodulatory effects than MSCs from other sources. DPSCs and their exosomes can exert an immunomodulatory ability by acting on target immune cells to regulate cytokines. DPSCs can also migrate to the lesion site to differentiate into target cells to repair the injured tissue, and play an important role in tissue regeneration. The aim of this review is to summarize the molecular mechanism and target cells of the immunomodulatory effects of DPSCs, and the latest advances in preclinical research in the treatment of various immune-mediated diseases, providing new reflections for their clinical application. DPSCs may be a promising source of stem cells for the treatment of immune-mediated diseases.

Investigation of the Effects of Monomeric and Dimeric Stilbenoids on Bacteria-Induced Cytokines and LPS-Induced ROS Formation in Bone Marrow-Derived Dendritic Cells

Stilbenoids are anti-inflammatory and antioxidant compounds, with resveratrol being the most investigated molecule in this class. However, the actions of most other stilbenoids are much less studied. This study compares five monomeric (resveratrol, piceatannol, pterostilbene, pinostilbene, and trimethoxy-resveratrol) and two dimeric (dehydro-δ-viniferin and trans-δ-viniferin) stilbenoids for their capability to modulate the production of bacteria-induced cytokines (IL-12, IL-10, and TNF-α), as well as lipopolysaccharide (LPS)-induced reactive oxygen species (ROS), in murine bone marrow-derived dendritic cells. All monomeric species showed dose-dependent inhibition of E. coli-induced IL-12 and TNF-α, whereas only resveratrol and piceatannol inhibited IL-10 production. All monomers, except trimethoxy-resveratrol, inhibited L. acidophilus-induced IL-12, IL-10, and TNF-α production. The dimer dehydro-δ-viniferin remarkably enhanced L. acidophilus-induced IL-12 production. The contrasting effect of resveratrol and dehydro-δ-viniferin on IL-12 production was due, at least in part, to a divergent inactivation of the mitogen-activated protein kinases by the two stilbenoids. Despite having moderate to high total antioxidant activity, dehydro-δ-viniferin was a weak inhibitor of LPS-induced ROS formation. Conversely, resveratrol and piceatannol potently inhibited LPS-induced ROS formation. Methylated monomers showed a decreased antioxidant capacity compared to resveratrol, also depending on the methylation site. In summary, the immune-modulating effect of the stilbenoids depends on both specific structural features of tested compounds and the stimulating bacteria.

Role of lymphocyte immunization therapy (LIT) in repeated miscarriages - A review

Recurrent Miscarriages are seen in 2%-5% of women and 50% of these are labelled as unexplained as no underlying cause is found in them. Various studies have explained possible alloimmune basis in these couples. Lymphocyte Immunization Therapy (LIT) was the earliest immunomodulatory method suggested in these cases. The efficacy of LIT was questioned by REMIS study in 1999 and subsequent Cochrane reviews. However, recent meta-analyses have shown that LIT is not only effective in the treatment of repeated miscarriages but it is also safe. Review of the odds ratio for live birth of various meta-analyses of studies in recurrent miscarriages has also shown that newer meta-analyses have shown higher odds ratios. The purpose of this paper is to put forward the current perspective of LIT in reproductive failure and bring forth the recent evidence. In addition, we share our experience with the use of LIT in women with recurrent pregnancy losses. However, large multicentric RCTs are required to further prove efficacy of LIT.

Secretomes derived from osteogenically differentiated jaw periosteal cells inhibit phenotypic and functional maturation of CD14+ monocyte-derived dendritic cells

The jaw periosteal tissue is generally recognized as a suitable source for the isolation of mesenchymal stem cells (MSCs). In previous studies we showed evidence that two- and three-dimensionally cultured jaw periosteum-derived MSCs (JPCs) are able to induce a more immature phenotype of dendritic cells (DCs). To further expand our knowledge of JPCs' immunoregulative function, we investigated the effects of JPC secretomes derived from undifferentiated (CO) or osteogenically differentiated cells (treated with or without dexamethasone: OB+/-D) on CD14⁺ monocyte-derived DCs (MoDCs). We detected a remarkably reduced formation of MoDC homotypic clusters under the influence of secretomes from osteogenically induced JPCs. Further, significantly decreased numbers of CD83⁺ cells, up-regulated CD209 and down-regulated CD80, CD86 and CD197 expression levels were detected on the surface of MoDCs. Whereas secretomes from JPCs osteogenically stimulated with dexamethasone significantly enhanced FITC-dextran uptake capacity of MoDCs, the increase by secretomes of JPCs treated without dexamethasone did not reach significance. The analysis of mixed lymphocyte reactions revealed that OB+/-D secretomes were able to significantly reduce the numbers of proliferating CD14^- peripheral blood mononuclear cells (PBMCs) and of proliferating CD4⁺ T cells. The OB-D secretome significantly promoted the expansion of regulatory CD25⁺ T cells. Regarding gene expression of MoDCs, remarkably up-regulated mRNA expression of CD209, HLA-DRA, CSF3, IL10 and IL8 was detected when DCs were cultured in the presence of OB+/-D secretomes. At the same time, secretomes seemed to have an impact in the down-regulation of IFNγ and IL12B gene expression. At protein level, OB+/-D secretomes significantly up-regulated IL-10 and IDO (indoleamine-pyrrole 2,3-dioxygenase) levels whereas IL-12/IL-23p40 levels were down-regulated in supernatants of MoDCs when cultured under the presence of OB+/-D secretomes. Taken together, while secretomes from untreated JPCs had only little effects on the process of maturation of MoDCs, secretomes derived from osteogenically induced JPCs were able to inhibit the phenotypic and functional maturation of MoDCs.

Endotoxin-Tolerance Mimicking to Study TLR in Promotion of Tolerogenic DCs and Tr1 Cells

Dendritic cells (DCs) are key regulators of immunogenic and tolerogenic immune responses. Both these immune responses require DCs respectively to activate effector T cells or to induce their anergy and T regulatory activity. Modifications of DCs in the laboratory and several pharmacological agents can enhance and stabilize their tolerogenic properties. Recent evidences demonstrate that activation of specific toll-like receptors (TLRs) can be involved in induction of DCs with tolerogenic properties able to initiate T regulatory cell responses.In the present chapter, we show a detail protocol to obtain in vitro regulatory conventional DCs (cDCs) in response to repeated exposure to lipopolysaccharide (LPS), a ligand of TLR4, by mimicking the mechanism of endotoxin tolerance. Subsequently, the protective effect of cDCs' conditionate with LPS will be describe in in vivo inflammatory model of endotoxemia. Finally, we illustrate the method to study the ability of LPS-conditionate cDCs to promote T regulatory cells in ex vivo system.

Targeted Cancer Immunotherapy: Nanoformulation Engineering and Clinical Translation

With the rapid growth of advanced nanoengineering strategies, there are great implications for therapeutic immunostimulators formulated in nanomaterials to combat cancer. It is crucial to direct immunostimulators to the right tissue and specific immune cells at the right time, thereby orchestrating the desired, potent, and durable immune response against cancer. The flexibility of nanoformulations in size, topology, softness, and multifunctionality allows precise regulation of nano-immunological activities for enhanced therapeutic effect. To grasp the modulation of immune response, research efforts are needed to understand the interactions of immune cells at lymph organs and tumor tissues, where the nanoformulations guide the immunostimulators to function on tissue specific subsets of immune cells. In this review, recent advanced nanoformulations targeting specific subset of immune cells, such as dendritic cells (DCs), T cells, monocytes, macrophages, and natural killer (NK) cells are summarized and discussed, and clinical development of nano-paradigms for targeted cancer immunotherapy is highlighted. Here the focus is on the targeting nanoformulations that can passively or actively target certain immune cells by overcoming the physiobiological barriers, instead of directly injecting into tissues. The opportunities and remaining obstacles for the clinical translation of immune cell targeting nanoformulations in cancer therapy are also discussed.

The Dendritic Cell Dilemma in the Skin: Between Tolerance and Immunity

Dendritic cells (DC) are uniquely capable of initiating and directing immune responses. The range of their activities grounds in the heterogeneity of DC subsets and their functional plasticity. Numerical and functional DC changes influence the development and progression of disease, and correction of such dysregulations has the potential to treat disease causally. In this review, we discuss the major advances in our understanding of the regulation of DC lineage formation, differentiation, and function in the skin. We describe the alteration of DC in disease as well as possibilities for therapeutic reprogramming with a focus on tolerogenic DC. Because regulatory T cells (Treg) are indispensable partners of DC in the induction and control of tolerance, we pay special attention to the interactions with these cells. Above all, we would like to arouse fascination for this cell type and its therapeutic potential in skin diseases.

Loricrin at the Boundary between Inside and Outside

Cornification is a specialized mode of the cell-death program exclusively allowed for terrestrial amniotes. Recent investigations suggest that loricrin (LOR) is an important cornification effector. As the connotation of its name (“lorica” meaning an armor in Latin) suggests, the keratin-associated protein LOR promotes the maturation of the epidermal structure through organizing covalent cross-linkages, endowing the epidermis with the protection against oxidative injuries. By reviewing cornification mechanisms, we seek to classify ichthyosiform dermatoses based on their function, rather than clinical manifestations. We also reviewed recent mechanistic insights into the Kelch-like erythroid cell-derived protein with the cap “n” collar homology-associated protein 1/nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway in skin health and diseases, as LOR and NRF2 coordinate the epidermis-intrinsic xenobiotic metabolism. Finally, we refine the theoretical framework of cross-talking between keratinocytes and epidermal resident leukocytes, dissecting an LOR immunomodulatory function.

JAK1 signaling in dendritic cells promotes peripheral tolerance in autoimmunity through PD-L1-mediated regulatory T cell induction

Dendritic cells (DCs) induce peripheral T cell tolerance, but cell-intrinsic signaling cascades governing their stable tolerogenesis remain poorly defined. Janus Kinase 1 (JAK1) transduces cytokine-receptor signaling, and JAK inhibitors (Jakinibs), including JAK1-specific filgotinib, break inflammatory cycles in autoimmunity. Here, we report in heterogeneous DC populations of multiple secondary lymphoid organs that JAK1 promotes peripheral T cell tolerance during experimental autoimmune encephalomyelitis (EAE). Mice harboring DC-specific JAK1 deletion exhibit elevated peripheral CD4+ T cell expansion, less regulatory T cells (Tregs), and worse EAE outcomes, whereas adoptive DC transfer ameliorates EAE pathogenesis by inducing peripheral Tregs, programmed cell death ligand 1 (PD-L1) dependently. This tolerogenic program is substantially reduced upon the transfer of JAK1-deficient DCs. DC-intrinsic IFN-γ-JAK1-STAT1 signaling induces PD-L1, which is required for DCs to convert CD4+ T cells into Tregs in vitro and attenuated upon JAK1 deficiency and filgotinib treatment. Thus, DC-intrinsic JAK1 promotes peripheral tolerance, suggesting potential unwarranted DC-mediated effects of Jakinibs in autoimmune diseases.

Spatiotemporal Adaptations of Macrophage and Dendritic Cell Development and Function

Macrophages and conventional dendritic cells (cDCs) are distributed throughout the body, maintaining tissue homeostasis and tolerance to self and orchestrating innate and adaptive immunity against infection and cancer. As they complement each other, it is important to understand how they cooperate and the mechanisms that integrate their functions. Both are exposed to commensal microbes, pathogens, and other environmental challenges that differ widely among anatomical locations and over time. To adjust to these varying conditions, macrophages and cDCs acquire spatiotemporal adaptations (STAs) at different stages of their life cycle that determine how they respond to infection. The STAs acquired in response to previous infections can result in increased responsiveness to infection, termed training, or in reduced responses, termed paralysis, which in extreme cases can cause immunosuppression. Understanding the developmental stage and location where macrophages and cDCs acquire their STAs, and the molecular and cellular players involved in their induction, may afford opportunities to harness their beneficial outcomes and avoid or reverse their deleterious effects. Here we review our current understanding of macrophage and cDC development, life cycle, function, and STA acquisition before, during, and after infection. We propose a unified framework to explain how these two cell types adjust their activities to changing conditions over space and time to coordinate their immunosurveillance functions. Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Comprehensive analysis of DOK family genes expression, immune characteristics, and drug sensitivity in human tumors

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The expression of DOK family genes is related to overall survival (OS), clinical stage, tumor mutation, methylation, CNV, and SNV.

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DOK family genes are significantly associated with poor prognosis of UVM.

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DOK1-DOK3 has obvious correlation with tumor immunity and tumor microenvironment.

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DOK family gene is significantly related to tumor stemness and drug sensitivity.

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The expression of DOK family genes is related to the activation of EMT and hormone ER pathways, and is related to the inhibition of DNA damage response, cell cycle, and hormone AR pathways.

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DOK1 and DOK3, DOK2 and DOK3 have the significant correlation.

Introduction

Objectives

Methods

Results

Conclusions

Fascinating Dendritic Cells—Sentinel Cells of the Immune System a Review

Dendritic cells (DC) are specialized antigen presenting cells which have the unique ability to activate naive T-lymphocytes. Their role in the immune system is much more sophisticated than it seems, as they do not kill the pathogens directly, but provide a long-lasting antigen specific immune response thanks to that sufficiently bridging the innate and the adaptive immunity. In recent years, there has been a growing interest in studies of their role in immune regulation, autoimmune reactions, as well as in immune responses against pathogens and tumours. Processing and presentation capabilities of a highly specific and unique tumour antigen makes them an interesting tool for stimulating effective anti-tumour immunity. In vitro generations of DC represent a preferred model for more detailed studies of DC biology in other fields. The aim of this review was to discuss the main role of dendritic cells in the body as well as their current use as experimental models for further scientific studies.

Impact of intrarectal chromofungin treatment on dendritic cells-related markers in different immune compartments in colonic inflammatory conditions

BACKGROUND

Chromofungin (CHR: chromogranin-A 47-66) is a chromogranin-A derived peptide with anti-inflammatory and anti-microbial properties. Ulcerative colitis (UC) is characterized by a colonic decrease of CHR and a dysregulation of dendritic CD11c⁺ cells.

AIM

To investigate the association between CHR treatment and dendritic cells (DCs)-related markers in different immune compartments in colitis.

METHODS

A model of acute UC-like colitis using dextran sulphate sodium (DSS) was used in addition to biopsies collected from UC patients.

RESULTS

Intrarectal CHR treatment reduced the severity of DSS-induced colitis and was associated with a significant decrease in the expression of CD11c, CD40, CD80, CD86 and interleukin (IL)-12p40 in the inflamed colonic mucosa and CD11c, CD80, CD86 IL-6 and IL-12p40 within the mesenteric lymph nodes and the spleen. Furthermore, CHR treatment decreased CD80 and CD86 expression markers of splenic CD11c⁺ cells and decreased NF-κB expression in the colon and of splenic CD11c⁺ cells. In vitro, CHR decreased CD40, CD80, CD86 IL-6 and IL-12p40 expression in naïve bone marrow-derived CD11c⁺ DCs stimulated with lipopolysaccharide. Pharmacological studies demonstrated an impact of CHR on the NF-κB pathway. In patients with active UC, CHR level was reduced and showed a negative linear relationship with CD11c and CD86.

CONCLUSION

CHR has protective properties against intestinal inflammation via the regulation of DC-related markers and CD11c⁺ cells. CHR could be a potential therapy of UC.

Peripheral immune tolerance by prolactin-induced protein originated from human invariant natural killer T cells

invariant natural killer T (iNKT) cells have been reported to regulate a diverse set of immunological responses. iNKT cell dysfunction in cytokine secretion is linked to the development of autoimmunity, an immune response against its own tissue. Interestingly, CD4+ iNKT cells preferentially secrete regulatory cytokines. Here we investigated what kind of secreting factors of it are involved in dendritic cell (DC) maturation to regulate immune responses. We found one of them, prolactin induced protein (PIP), from the supernatants of cultured CD4+ iNKT cells. It was validated using RT-quantitative real-time polymerase chain reaction (RT-qPCR) and western blot analysis. Subsequent analysis upon PIP treatment was performed using fluorescence-activated cell sorting (FACS) analysis. We identified PIP as one of strong candidates for inducing DC maturation, to similar level to lipopolysaccharide, an already known candidate molecule. Recombinant PIP recapitulated natural function, and induction of DC differentiation by both recombinant and purified PIP was blocked by anti-Toll-like receptor (TLR)2 antibody (Ab), but not by anti-TLR4/5 or anti-receptor Ab for advanced glycation end product Ab. Interestingly, PIP induced the differentiation of naïve T cells into CD4+ CD25+ Foxp3+ regulatory T cells and reduced the number of helper T (Th)1 and Th17 cells produced by Pam3CysSerLys4. Take in together, these results suggest that PIP is an important factor that mediates immunoregulation by iNKT cells through TLR2-mediated signaling.

Mannose-modified liposome designed for epitope peptide drug delivery in cancer immunotherapy

BACKGROUND

Based on the interaction between cytotoxic T lymphocyte (CTL) dominant epitopes and dendritic cells (DCs), CD8⁺T cells are specifically activated into CTL cells. Targeted killing is a type of tumor vaccine for immunotherapy with great development potential. However, because of the disadvantages of poor stability in vivo and low uptake rate of DCs caused by single use of dominant epitope peptide drugs, its use is limited. Here, we investigated the antitumor potential of M-YL/LA-Lipo, a novel liposome drug delivery system.

METHODS

We assembled mannose on the surface of liposome, which has a highly targeted effect on the mannose receptor on the surface of DCs. The dominant epitope peptide drugs were encapsulated into the liposome using membrane hydration method, and the encapsulation rate, release rate, in vitro stability, and microstructure were characterized using ultrafiltration method, dialysis method, and negative staining transmission electron microscopy. In addition, its targeting ability was verified by in vitro interaction with DCs, and its anticancer effect was verified by animal experiments.

RESULTS

We have successfully prepared a liposome drug delivery system with stable physical and chemical properties. Moreover, we demonstrated that it was highly uptaken by DCs and promoted DC maturation in vitro. Furthermore, in vivo animal experiments indicated that M-YL/LA-Lipo specific CTL significantly inhibited the hematogenous spread of lung metastasis of triple negative breast cancer.

CONCLUSIONS

we successfully constructed a new polypeptide liposome drug delivery system by avoiding the disadvantages of single use of dominant epitope peptide drugs and accurate targeted therapy for tumors.

Ubiquitin Ligases CBL and CBL-B Maintain the Homeostasis and Immune Quiescence of Dendritic Cells

Dendritic cells (DCs) are composed of multiple lineages of hematopoietic cells and orchestrate immune responses upon detecting the danger and inflammatory signals associated with pathogen and damaged tissues. Under steady-state, DCs are maintained at limited numbers and the functionally quiescent status. While it is known that a fine balance in the DC homeostasis and activation status is also important to prevent autoimmune diseases and hyperinflammation, mechanisms that control DC development and activation under stead-state remain not fully understood. Here we show that DC-specific ablation of CBL and CBL-B (CBL^-/-CBL-B^-/-) leads to spontaneous liver inflammation and fibrosis and early death of the mice. The mutant mice have a marked expansion of classic CD8α⁺/CD103⁺ DCs (cDC1s) in peripheral lymphoid organs and the liver. These DCs exhibit atypical activation phenotypes characterized by an increased production of inflammatory cytokines and chemokines but not the cell surface MHC-II and costimulatory ligands. While the mutant mice also have massive T cell activation, lymphocytes are not required for the disease development. The CBL^-/-CBL-B^-/- mutation enhances FLT3-mTOR signaling, due to defective FLT3 ubiquitination and degradation. Blockade of FLT3-mTOR signaling normalizes the homeostasis of cDC1s and attenuates liver inflammation. Our result thus reveals a critical role of CBLs in the maintenance of DC homeostasis and immune quiescence. This regulation could be relevant to liver inflammatory diseases and fibrosis in humans.

Review: Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform

Vaccination is the most effective way to prevent coronavirus disease 2019 (COVID-19). Vaccine development approaches consist of viral vector vaccines, DNA vaccine, RNA vaccine, live attenuated virus, and recombinant proteins, which elicit a specific immune response. The use of nanoparticles displaying antigen is one of the alternative approaches to conventional vaccines. This is due to the fact that nano-based vaccines are stable, able to target, form images, and offer an opportunity to enhance the immune responses. The diameters of ultrafine nanoparticles are in the range of 1-100 nm. The application of nanotechnology on vaccine design provides precise fabrication of nanomaterials with desirable properties and ability to eliminate undesirable features. To be successful, nanomaterials must be uptaken into the cell, especially into the target and able to modulate cellular functions at the subcellular levels. The advantages of nano-based vaccines are the ability to protect a cargo such as RNA, DNA, protein, or synthesis substance and have enhanced stability in a broad range of pH, ambient temperatures, and humidity for long-term storage. Moreover, nano-based vaccines can be engineered to overcome biological barriers such as nonspecific distribution in order to elicit functions in antigen presenting cells. In this review, we will summarize on the developing COVID-19 vaccine strategies and how the nanotechnology can enhance antigen presentation and strong immunogenicity using advanced technology in nanocarrier to deliver antigens. The discussion about their safe, effective, and affordable vaccines to immunize against COVID-19 will be highlighted.

Revisiting Current Concepts on the Tolerogenicity of Steady-State Dendritic Cell Subsets and Their Maturation Stages

The original concept stated that immature dendritic cells (DC) act tolerogenically whereas mature DC behave strictly immunogenically. Meanwhile, it is also accepted that phenotypically mature stages of all conventional DC subsets can promote tolerance as steady-state migratory DC by transporting self-antigens to lymph nodes to exert unique functions on regulatory T cells. We propose that in vivo 1) there is little evidence for a tolerogenic function of immature DC during steady state such as CD4 T cell anergy induction, 2) all tolerance as steady-state migratory DC undergo common as well as subset-specific molecular changes, and 3) these changes differ by quantitative and qualitative markers from immunogenic DC, which allows one to clearly distinguish tolerogenic from immunogenic migratory DC.

Dendrimeric HIV-peptide delivery nanosystem affects lipid membranes structure

The aim of this study was to evaluate the nature and mechanisms of interaction between HIV peptide/dendrimer complexes (dendriplex) and artificial lipid membranes, such as large unilayered vesicles (LUV) and lipid monolayers in the air-water interface. Dendriplexes were combined as one of three HIV-derived peptides (Gp160, P24 and Nef) and one of two cationic phosphorus dendrimers (CPD-G3 and CPD-G4). LUVs were formed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) or of a mixture of DMPC and dipalmitoyl-phosphatidylglycerol (DPPG). Interactions between dendriplexes and vesicles were characterized by dynamic light scattering (DLS), fluorescence anisotropy, differential scanning calorimetry (DSC) and Langmuir-Blodgett methods. The morphology of formed systems was examined by transmission electron microscopy (TEM). The results suggest that dendriplexes interact with both hydrophobic and hydrophilic regions of lipid bilayers. The interactions between dendriplexes and negatively charged lipids (DMPC-DPPG) were stronger than those between dendriplexes and liposomes composed of zwitterionic lipids (DMPC). The former were primarily of electrostatic nature due to the positive charge of dendriplexes and the negative charge of the membrane, whereas the latter can be attributed to disturbances in the hydrophobic domain of the membrane. Obtained results provide new information about mechanisms of interaction between lipid membranes and nanocomplexes formed with HIV-derived peptides and phosphorus dendrimers. These data could be important for the choosing the appropriate antigen delivery vehicle in the new vaccines against HIV infection.

Intestinal cDC1 drive cross-tolerance to epithelial-derived antigen via induction of FoxP3+CD8+ Tregs

Although CD8⁺ T cell tolerance to tissue-specific antigen (TSA) is essential for host homeostasis, the mechanisms underlying peripheral cross-tolerance and whether they may differ between tissue sites remain to be fully elucidated. Here, we demonstrate that peripheral cross-tolerance to intestinal epithelial cell (IEC)-derived antigen involves the generation and suppressive function of FoxP3⁺CD8⁺ T cells. FoxP3⁺CD8⁺ T_reg generation was dependent on intestinal cDC1, whose absence led to a break of tolerance and epithelial destruction. Mechanistically, intestinal cDC1-derived PD-L1, TGFβ, and retinoic acid contributed to the generation of gut-tropic CCR9⁺CD103⁺FoxP3⁺CD8⁺ T_regs Last, CD103-deficient CD8⁺ T cells lacked tolerogenic activity in vivo, indicating a role for CD103 in FoxP3⁺CD8⁺ T_reg function. Our results describe a role for FoxP3⁺CD8⁺ T_regs in cross-tolerance in the intestine for which development requires intestinal cDC1.

Characterization and Manipulation of the Crosstalk Between Dendritic and Natural Killer Cells Within the Tumor Microenvironment

Cellular therapy has entered the daily clinical life with the approval of CAR T cell therapeutics and dendritic cell (DCs) vaccines in the US and the EU. In addition, numerous other adoptive cellular products, including natural killer (NK) cells, are currently evaluated in early phase I/ II clinical trials for the treatment of cancer patients. Despite these promising accomplishments, various challenges remain to be mastered in order to ensure sustained therapeutic success. These include the identification of strategies by which tumor cells escape the immune system or establish an immunosuppressive tumor microenvironment (TME). As part of the innate immune system, DCs and NK cells are both present within the TME of various tumor entities. While NK cells are well known for their intrinsic anti-tumor activity by their cytotoxicity capacities and the secretion of pro-inflammatory cytokines, the role of DCs within the TME is a double-edged sword as different DC subsets have been described with either tumor-promoting or -inhibiting characteristics. In this review, we will discuss recent findings on the interaction of DCs and NK cells under physiological conditions and within the TME. One focus is the crosstalk of various DC subsets with NK cells and their impact on the progression or inhibition of tumor growth. In addition, we will provide suggestions to overcome the immunosuppressive outcome of the interaction of DCs and NK cells within the TME.

Inflammasomes in dendritic cells: Friend or foe?

Inflammasomes are cytosolic multiprotein complexes that crucially contribute to host defense against pathogens but are also involved in the pathogenesis of autoinflammatory diseases. Inflammasome formation leads to activation of effector caspases (caspase-1, 4, 5, or 11), the proteolytic maturation of IL-1β and IL-18 as well as cleavage of the pore-forming protein Gasdermin D. Dendritic cells are major regulators of immune responses as they bridge innate and adaptive immunity. We here summarize the current knowledge on inflammasome expression and formation in murine bone marrow-, human monocyte-derived as well as murine and human primary dendritic cells. Further, we discuss both, the beneficial and detrimental, involvement of inflammasome activation in dendritic cells in cancer, infections, and autoimmune diseases. As inflammasome activation is typically accompanied by Gasdermin d-mediated pyroptosis, which is an inflammatory form of programmed cell death, inflammasome formation in dendritic cells seems ill-advised. Therefore, we propose that hyperactivation, which is inflammasome activation without the induction of pyroptosis, may be a general model of inflammasome activation in dendritic cells to enhance Th1, Th17 as well as cytotoxic T cell responses.

CD137 Signaling Regulates Acute Colitis via RALDH2-Expressing CD11b-CD103+ DCs

CD137, a potent costimulatory receptor for CD8⁺ T cells, is expressed in various non-T cells, but little is known about its regulatory functions in these cells. In this study, we show that CD137 signaling, specifically in intestinal CD11b^-CD103⁺ dendritic cells (DCs), restricts acute colitis progression. Mechanistically, CD137 engagement activates TAK1 and subsequently stimulates the AMPK-PGC-1α axis to enhance expression of the Aldh1a2 gene encoding the retinoic acid (RA) metabolizing enzyme RALDH2. RA can act on CD11b⁺CD103^- DCs and induce SOCS3 expression, which, in turn, suppresses p38MAPK activation and interleukin-23 (IL-23) production. Administration of RA in DC-specific CD137^-/- mice represses IL-23-producing CD11b⁺CD103^- DCs and T_H17 cells, indicating that RA is a major inhibitory effector molecule against intestinal CD11b⁺CD103^- DCs. Additionally, the therapeutic effect of the anti-CD137 antibody is abrogated in DC-specific CD137^-/- mice. Taken together, our results define a mechanism of paracrine immunoregulation operating between adjacent DC subsets in the intestine.

Hepatic Dendritic Cells in the Development and Progression of Metabolic Steatohepatitis

Metabolic Associated Fatty liver disease (MAFLD) is a global health problem and represents the most common cause of chronic liver disease in the world. MAFLD spectrum goes from simple steatosis to cirrhosis, in between metabolic steatohepatitis with progressive fibrosis, which pathogenesis is not completely understood. Hence, the role of the immune system has become an important fact in the trigger of inflammatory cascades in metabolic steatohepatitis and in the activation of hepatic stellate cells (HSCs). Among, the more studied immune cells in the pathogenesis of MAFLD are macrophages, T cells, natural killer and dendritic cells. In particular, hepatic dendritic cells had recently attracted a special attention, with a dual role in the pathogenesis of MAFLD. These cells have the capacity to switch from a tolerant state to active state inducing an inflammatory cascade. Furthermore, these cells play a role in the lipid storage within the liver, having, thus providing a crucial nexus between inflammation and lipid metabolism. In this review, we will discuss the current knowledge on the dual role of dendritic cells in lipid accumulation, as wells as in the triggering of hepatic inflammation and hepatocytes cell death in metabolic steatohepatitis.

Bivalent therapeutic vaccine against HPV16/18 genotypes consisting of a fusion protein between the extra domain A from human fibronectin and HPV16/18 E7 viral antigens

Background

In vivo targeting of human papillomavirus (HPV) derived antigens to dendritic cells might constitute an efficient immunotherapeutic strategy against cervical cancer. In previous works, we have shown that the extra domain A from murine fibronectin (mEDA) can be used to target antigens to toll-like receptor 4 (TLR4) expressing dendritic cells and induce strong antigen-specific immune responses. In the present study, we have produced a bivalent therapeutic vaccine candidate consisting of the human EDA (hEDA) fused to E7 proteins from HPV16 and HPV18 (hEDA-HPVE7-16/18) and evaluate its potential as a therapeutic vaccine against cervical cancer.

Materials and methods

Recombinant fusion proteins containing HPV E7 proteins from HPV16 and HPV18 virus subtypes fused to hEDA were produced and tested in vitro on their capacity to bind TLR4 and induce the production of tumor necrosis factor-α or interleukin (IL)-12 by human monocytes and dendritic cells. The immunogenicity and potential therapeutic activity of the vaccine in combination with cisplatin or with the TLR3 agonist molecules polyinosinic‐polycytidylic acid (Poly IC) or Poly ICLC was evaluated in mice bearing subcutaneous or genital orthotopic HPV16 TC-1 tumors.

Results

hEDA-HPVE7-16/18 prototype vaccine binds human TLR4 and stimulate TLR4-dependent signaling pathways and IL-12 production by human monocyte-derived dendritic cell. Vaccination with hEDA-HPVE7-16/18 induced strong HPVE7-specific Cytotoxic T lymphocyte (CTL) responses and eliminated established tumors in the TC-1-based tumor model. The antitumor efficacy was significantly improved by combining the fusion protein with cisplatin or with the TLR-3 ligand Poly IC and especially with the stabilized analog Poly ICLC. Moreover, hEDA-HPVE7-16/18+Poly ICLC induced full tumor regression in 100% of mice bearing orthotopic genital HPV tumors.

Conclusion

Our results suggest that this therapeutic vaccine formulation may be an effective treatment for cervical tumors that do not respond to current therapies.

Manganese-Doped Silica-Based Nanoparticles Promote the Efficacy of Antigen-Specific Immunotherapy

Prophylactic human papillomavirus (HPV) vaccines are commercially available for prevention of infection with cancerogenic HPV genotypes but are not able to combat pre-existing HPV-associated disease. In this study, we designed a nanomaterial-based therapeutic HPV vaccine, comprising manganese (Mn⁴⁺)-doped silica nanoparticles (Mn⁴⁺-SNPs) and the viral neoantigen peptide GF001 derived from the HPV16 E7 oncoprotein. We show in mice that Mn⁴⁺-SNPs act as self-adjuvants by activating the inflammatory signaling pathway via generation of reactive oxygen species, resulting in immune cell recruitment to the immunization site and dendritic cell maturation. Mn⁴⁺-SNPs further serve as Ag carriers by facilitating endo/lysosomal escape via depletion of protons in acidic endocytic compartments and subsequent Ag delivery to the cytosol for cross-presentation. The Mn⁴⁺-SNPs+GF001 nanovaccine induced strong E7-specific CD8⁺ T cell responses, leading to remission of established murine HPV16 E7-expressing solid TC-1 tumors and E7-expressing transgenic skin grafts. This vaccine construct offers a simple and general strategy for therapeutic HPV and potentially other cancer vaccines.

Modularly Programmable Nanoparticle Vaccine Based on Polyethyleneimine for Personalized Cancer Immunotherapy

Nanoparticles (NPs) can serve as a promising vaccine delivery platform for improving pharmacological property and codelivery of antigens and adjuvants. However, NP-based vaccines are generally associated with complex synthesis and postmodification procedures, which pose technical and manufacturing challenges for tailor-made vaccine production. Here, modularly programmed, polyethyleneimine (PEI)-based NP vaccines are reported for simple production of personalized cancer vaccines. Briefly, PEI is conjugated with neoantigens by facile coupling chemistry, followed by electrostatic assembly with CpG adjuvants, leading to the self-assembly of nontoxic, sub-50 nm PEI NPs. Importantly, PEI NPs promote activation and antigen cross-presentation of antigen-presenting cells and cross-priming of neoantigen-specific CD8+ T cells. Surprisingly, after only a single intratumoral injection, PEI NPs with optimal PEGylation elicit as high as ≈30% neoantigen-specific CD8+ T cell response in the systemic circulation and sustain elevated CD8+ T cell response over 3 weeks. PEI-based nanovaccines exert potent antitumor efficacy against pre-established local tumors as well as highly aggressive metastatic tumors. PEI engineering for modular incorporation of neoantigens and adjuvants offers a promising strategy for rapid and facile production of personalized cancer vaccines.

Overcoming immune dysfunction in the elderly: trained immunity as a novel approach

People with advanced age have a higher susceptibility to infections and exhibit increased mortality and morbidity as the ability of the immune system to combat infections decreases with age. While innate immune cells display functional defects such as decreased phagocytosis, chemotaxis and cytokine production, adaptive immune cells exhibit reduced receptor diversity, defective antibody production and a sharp decline in naive cell populations. Successful responses to vaccination in the elderly are critical to prevent common infections such as influenza and pneumonia, but vaccine efficacy decreases in older individuals compared with young adults. Trained immunity is a newly emerging concept that showed that innate immune cells possess non-specific immunological memory established through epigenetic and metabolic reprogramming upon encountering certain pathogenic stimuli. Clinical studies suggest that trained immunity can be utilized to enhance immune responses against infections and improve the efficiency of vaccinations in adults; however, how trained immunity responses are shaped with advanced age is still an open question. In this review, we provide an overview of the age-related changes in the immune system with a focus on innate immunity, discuss current vaccination strategies for the elderly, present the concept of trained immunity and propose it as a novel approach to enhance responses against infections and vaccinations in the elderly population.

Cell Therapy for Liver Disease: From Promise to Reality

Over the last decade, there has been a considerable progress in the development of cell therapy products for the treatment of liver diseases. The quest to generate well-defined homogenous cell populations with defined mechanism(s) of action has enabled the progression from use of autologous bone marrow stem cells comprising of heterogeneous cell populations to allogeneic cell types such as monocyte-derived macrophages, regulatory T cells, mesenchymal stromal cells, macrophages, etc. There is growing evidence regarding the multiple molecular mechanisms pivotal to various therapeutic effects and hence, careful selection of cell therapy product for the desired putative effects is crucial. In this review, we have presented an overview of the cell therapies that have been developed thus far, with preclinical and clinical evidence for their use in liver disease. Limitations associated with these therapies have also been discussed. Despite the advances made, there remain multiple challenges to overcome before cell therapies can be considered as viable treatment options, and these include larger scale clinical trials, scalable production of cells according to good manufacturing practice standards, pathways for delivery of cell therapy within hospital environments, and costs associated with the production.

Peripherally-sourced myeloid antigen presenting cells increase with advanced aging

Aging is associated with dysfunction of the gut microbiota-immune-brain axis, a major regulatory axis in both brain health and in central nervous system (CNS) diseases. Antigen presenting cells (APCs) play a major role in sensing changes in the gut microbiota and regulation of innate and adaptive immune responses. APCs have also been implicated in various chronic inflammatory conditions, including age-related neurodegenerative diseases. The increase in chronic low-level inflammation seen with aging has also been linked to behavioral decline. Despite their acknowledged importance along the gut microbiota-immune-brain axis, there is limited evidence on how APCs change with aging. In this study, we examined age-related changes in myeloid APCs in the gut, spleen, and brain as well as changes in the gut microbiota and behavioral phenotype in mice ranging in age from 2 months up to 32 months of both sexes. Our data show that the number of peripherally-sourced myeloid APCs significantly increases with advanced aging in the brain. In addition, our data showed that age-related changes in APCs are subset-specific in the gut and sexually dimorphic in the spleen. Our work highlights the importance of studying myeloid APCs in an age-, tissue-, and sex-specific manner.

Manipulation of Regulatory Dendritic Cells for Induction Transplantation Tolerance

Current organ transplantation therapy is life-saving but accompanied by well-recognized side effects due to post-transplantation systematic immunosuppressive treatment. Dendritic cells (DCs) are central instigators and regulators of transplantation immunity and are responsible for balancing allograft rejection and tolerance. They are derived from monocyte-macrophage DC progenitors originating in the bone marrow and are classified into different subsets based on their developmental, phenotypical, and functional criteria. Functionally, DCs instigate allograft immunity by presenting donor antigens to alloreactive T cells via direct, indirect, and semidirect recognition pathways and provide essential signaling for alloreactive T cell activation via costimulatory molecules and pro-inflammatory cytokines. Regulatory DCs (DCregs) are characterized by a relatively low expression of major histocompatibility complex, costimulatory molecules, and altered cytokine production and exert their regulatory function through T cell anergy, T cell deletion, and regulatory T cell induction. In rodent transplantation studies, DCreg-based therapy, by in situ targeting or infusion of ex vivo generated DCregs, exhibits promising potential as a natural, well-tolerated, organ-specific therapeutic strategy for promoting lasting organ-specific transplantation tolerance. Recent early-phase studies of DCregs have begun to examine the safety and efficacy of DCreg-induced allograft tolerance in living-donor renal or liver transplantations. The present review summarizes the basic characteristics, function, and translation of DCregs in transplantation tolerance induction.

Mir-27a-3p attenuates bronchiolitis obliterans in vivo via the regulation of dendritic cells' maturation and the suppression of myofibroblasts' differentiation

Bronchiolitis obliterans (BO), is a chronic rejection phenotype characterized by chronic small airway fibrous obliteration, hinders the patients who suffer from lung transplanting for surviving longer. Cell-based therapies using dendritic cells (DCs) and T regulatory cells (Tregs) have been developed to regulate allograft rejection, and to induce and maintain immune tolerance. In the present study, the effects of mir-27a-3p on regulating DCs as well as resulting effects on BO attenuation have been investigated. According to our reporter assays, the potential targets of mir-27a-3p were Smad2, sprouty2, and Smad4, respectively. Furthermore, sprouty2 inhibition by mir-27-3p indirectly activated extracellular regulated protein kinases (ERK) and increased IL-10 production in DCs. This led to a positive feedback loop that maintained the immature state of DCs via IL-10/JAK/STAT3 pathway, and caused an increase in Foxp3⁺ CD4⁺ T cells amount as well as TGF-β level. Furthermore, mir-27a-3p regulated TGF-β function, inhibited TGF-β/Smad pathway, and suppressed myofibroblast differentiation through influencing the function of Smad2 and Smad4. In short, the study indicated the effect of mir-27a-3p on suppressing DC maturation, which implicated the potential clinical application in treating postlung transplant BO.