Plasmacytoid Dendritic Cells: Development, Regulation, and Function

Altered X-chromosome inactivation of the TLR7/8 locus and heterogeneity of pDCs in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease that has a strong female predominance. Both the X-linked TLR7 and TLR8 can induce type I IFN (IFN-I) by plasmacytoid DCs (pDCs), which can promote fibrosis. We identified five subclusters of pDCs, including ISGhigh clusters that were over-represented in SSc patients. We observed that both TLR7 and TLR8 genes escape from X chromosome inactivation (XCI) at higher frequency in pDCs of SSc patients, which was associated with changes in TLR7 protein profile. Combined DNA/RNA FISH analysis revealed that the TLR7/8 locus is preferentially located outside of the inactive X (Xi) territory when TLR7 is expressed, suggesting that higher-order loop formation is linked to TLR7/8 expression from the Xi. Furthermore, the expression levels of XIST and the transcriptional repressor SPEN were reduced in SSc pDCs. Hence, our data revealed the heterogeneity of pDCs in SSc and suggested that altered XCI at the TLR7/8 locus may contribute to the chronic IFN-I activity of pDCs in female SSc patients.

Mechanosensing regulates pDC activation in the skin through NRF2 activation

Plasmacytoid DCs (pDCs) infiltrate the skin, chronically produce type I interferon (IFN-I), and promote skin lesions and fibrosis in autoimmune patients. However, what controls their activation in the skin is unknown. Here, we report that increased stiffness inhibits the production of IFN-I by pDCs. Mechanistically, mechanosensing activates stress pathways including NRF2, which induces the pentose phosphate pathway and reduces pyruvate levels, a product necessary for pDC responses. Modulating NRF2 activity in vivo controlled the pDC response, leading to resolution or chronic induction of IFN-I in the skin. In systemic sclerosis (SSc) patients, although NRF2 was induced in skin-infiltrating pDCs, as compared with blood pDCs, the IFN response was maintained. We observed that CXCL4, a profibrotic chemokine elevated in fibrotic skin, was able to overcome stiffness-mediated IFN-I inhibition, allowing chronic IFN-I responses by pDCs in the skin. Hence, these data identify a novel regulatory mechanism exerted by the skin microenvironment and identify points of dysregulation of this mechanism in patients with skin inflammation and fibrosis.

Chimeric antigen receptor-modified T-cell therapy: Recent updates and challenges in autoimmune diseases

Chimeric antigen receptor (CAR) T-cell therapy (CAR-T) has revolutionized the treatment of hematologic malignancies, demonstrating significant clinical efficacy and leading to US Food and Drug Administration approval of several CAR T-cell-based products. This success has prompted exploration of CAR-T in other disease areas, including autoimmune diseases (AIDs). CAR-T targeting B cells has been shown to provide clinical and biological improvements in patients with refractory AIDs. The aim of this review is to discuss promising strategies involving CAR-T in AIDs, such as those targeting B cells and T cells, and to explore new approaches targeting fibroblasts or plasmacytoid dendritic cells. Despite these advances, the application of CAR-T in AIDs faces several unique challenges. The quality and functionality of T cells in patients with AIDs may be compromised as a result of previous treatments and the underlying inflammatory state, affecting the generation and efficacy of CAR-T. In addition, achieving adequate tissue biodistribution and persistence of CAR T cells in affected tissues remains a major challenge. Finally, the high costs associated with T-cell production pose economic problems, particularly in the context of chronic diseases, which are far more numerous than the hematologic diseases for which CAR-Ts have been granted marketing authorization to date. If the indications for CAR-T increase significantly, production costs will have to drop drastically in order to obtain reliable economic models.

Complex regulation of cardiac fibrosis: insights from immune cells and signaling pathways

Cardiac fibrosis is a physiological process that involves the formation of scar tissue in the heart in response to injury or damage. This process is initially a protective measure characterized by enhanced fibroblasts, which are responsible for producing extracellular matrix proteins that provide structural support to the heart. However, when fibrosis becomes excessive, it can lead to adverse outcomes, including increasing tissue stiffness and impaired cardiac function, which can ultimately result in heart failure with a poor prognosis. While fibroblasts are the primary cells involved in cardiac fibrosis, immune cells have also been found to play a vital role in its progression. Recent research has shown that immune cells exert multifaceted effects besides regulation of inflammatory response. Advanced research techniques such as single-cell sequencing and multiomics have provided insights into the specific subsets of immune cells involved in fibrosis and the complex regulation of the process. Targeted immunotherapy against fibrosis is gaining traction as a potential treatment option, but it is still unclear how immune cells achieve this regulation and whether distinct subsets are involved in different roles. To better understand the role of immune cells in cardiac fibrosis, it is essential to examine the classical signaling pathways that are closely related to fibrosis formation. We have also focused on the unique properties of diverse immune cells in cardiac fibrosis and their specific intercommunications. Therefore, this review will delve into the plasticity and heterogeneity of immune cells and their specific roles in cardiac fibrosis, which propose insights to facilitate the development of anti-fibrosis therapeutic strategies.

Genetic insights into the relationship between immune cell traits and abnormal uterine bleeding: A Mendelian randomization study

Abnormal uterine bleeding (AUB) is an inflammatory response involving immune cells, but the relationship between immune cell traits and AUB is highly complex and still largely unclear. This study utilized genetic data from a genome-wide association study of European participants. Mendelian randomization (MR) analysis methods, including inverse variance weighted (IVW) as the primary approach, weighted median, MR Egger regression, and Mendelian randomization pleiotropy residual sum and outlier, were employed for forward and reverse analyses. Sensitivity analyses validated the stability and reliability of the results. The IVW method indicated a potential causal relationship between CD45 on granulocyte (odds ratio [OR] = 0.916, 95% CI: 0.880-0.954, P = 1.974 × 10-5) with a decreased risk of menorrhagia. Two immune cell traits with P values < .001 were worthy of attention, CD25 on naive-mature B cell (OR = 0.935, 95% CI: 0.901-0.970, P = 3.882 × 10-4) may be associated with a decreased risk of menorrhagia, while human leukocyte antigen DR on plasmacytoid dendritic cell (OR = 1.089, 95% CI: 1.038-1.143, P = 5.126 × 10-4) may be associated with an increased risk of amenorrhea. No reverse causation was observed. Sensitivity analysis suggested no heterogeneity or horizontal pleiotropy (P > .05). No immune cell traits associated with or potentially related to oligomenorrhea were found. This MR study highlights the complex relationship between immune cell traits and AUB, offering insights into AUB's pathogenesis and potential biomarkers. Further clinical and in vitro validation is needed to assess these findings, with future research exploring immune modulation therapies for early diagnosis and personalized treatment.

Ebola Virus Infection of Flt3-Dependent, Conventional Dendritic Cells and Antigen Cross-presentation Leads to High Levels of T-Cell Activation

BACKGROUND

Previous studies have described that Ebola virus (EBOV) infection of human monocyte-derived dendritic cells (moDCs) inhibits dendritic cell (DC) maturation, resulting in poor T-cell activation. However, it is unknown how other DC subsets distinct from moDCs respond to EBOV infection.

METHODS

To better understand how DCs initiate T-cell activation during EBOV infection, we assessed the response of conventional mouse DCs (cDCs) to EBOV infection utilizing a recombinant EBOV expressing the model antigen ovalbumin.

RESULTS

In contrast to moDCs, mouse cDC2s and cDC1s were poorly infected with EBOV but were highly activated. DCs were able to prime CD8 T cells via cross-presentation of antigens obtained from cell debris of EBOV-infected cells. EBOV infection further enhanced DC cross-presentation.

CONCLUSIONS

Our findings indicate that EBOV infection of cDCs results in activation rather than inhibition, leading to high levels of T-cell activation. With that we propose a mechanistic explanation for the excess T-cell activation observed in human Ebola virus disease.

Structural analysis of Spi-B DNA-binding Ets domain recognizing 5'-AGAA-3' and 5'-GGAA-3' sequences

Plasmacytoid dendritic cells produce large amounts of type-I interferon (IFN-I) upon sensing nucleic acid components of pathogens by Toll-like receptors (TLR7 and TLR9). The transcription factor Spi-B has the DNA-binding Ets domain, and transactivates the Ifna4 promoter co-operatively with IFN regulatory factor-7 (IRF-7) for TLR7/TLR9-induced IFN-I production. Spi-B associates with IRF-7, and activates transcription by binding to the 5'-AGAA-3' sequence, being different from 5'-GGAA-3', known as the Ets domain recognition sequence. To understand the molecular mechanism for the co-operative transactivation of the Ifna4 promoter by Spi-B and IRF-7, we performed X-ray structural determination of the Spi-B Ets domain in complex with target DNAs, including 5'-AGAA-3' and 5'-GGAA-3' sequences. Furthermore, we conducted a modeling study of the complex of the Spi-B and IRF-7 with Ifna4 promoter DNA. X-ray structures showed that the binding of the Spi-B Ets domain induces a kink in DNA at the recognition sequence, and a more kinked DNA structure was observed in 5'-AGAA-3' than 5'-GGAA-3'. A modeling study showed that the Spi-B-induced kinked DNA structure in 5'-AGAA-3' is favorable for Spi-B and IRF-7 to approach each other for association on DNA.

KLK7 Involvement in Thyroid Papillary Carcinoma Cell Migration and Invasion by EMT via MAPK/ERK Pathways

Purpose: KLK7, also known as Kallikrein 7, is a secreted enzyme classified as a serine protease. Earlier studies have indicated that KLK7, KLK10, and KLK11 are linked to the survival rates and immune reactions of individuals with papillary thyroid cancer (PTC). This research examines KLK7, investigating its role and expression, and evaluates its viability as a treatment target for PTC. Methods: Initially, we examined the expression and possible functions of KLK7 in PTC using bioinformatics techniques. Researchers examined the impact of KLK7 on the cancer characteristics of PTC and explored if KLK7 influences the Epithelial-mesenchymal transition (EMT) process via the MAPK/ERK pathway in PTC using methods like immunohistochemistry and growth curve analysis. Ultimately, a model using a nude mouse was conducted to confirm the impact of KLK7 on PTC. Results: Our research demonstrated that KLK7 exhibited variations in THCA tissues, and KLK7-related genes had the role of participating in protein synthesis, genetic variation, mRNA degradation and immune microenvironment of PTC. KLK7 was upregulated in PTC tissues and positively associated with clinical stage and lymph node metastasis. Furthermore, the inhibition of KLK7 significantly diminished the proliferation, migration, and invasiveness of PTC cells. Notably, silencing KLK7 reduced phosphorylation of ERK1/2 and suppression of EMT. In vivo experiments further supported these findings. KLK7 might serve as an efficacious therapeutic target and predictive biomarker for PTC patients. Conclusion: KLK7 could be essential in the cancerous advancement of PTC by influencing the EMT via the MAPK/ERK signaling pathway, thereby impacting the growth, migration, and invasiveness of PTC cells. KLK7 appears to be a promising candidate for targeting in PTC therapy.

The tumor microenvironment and dendritic cells: Developers of pioneering strategies in colorectal cancer immunotherapy?

Colorectal cancer (CRC) is the world's third most frequent cancer, and both its incidence and fatality rates are rising. Despite various therapeutic approaches, neither its mortality rate nor its recurrence frequency has decreased significantly. Additionally, conventional treatment approaches, such as chemotherapy and radiotherapy, have several side effects and risks for patients with CRC. Accordingly, the need for alternative and effective treatments for CRC patients is critical. Immunotherapy that utilizes dendritic cells (DCs) harnesses the patient's immune system to combat cancer cells effectively. DCs are the most potent antigen-presenting cells (APCs), which play a vital role in generating anti-cancer T cell responses. A significant barrier to the immune system's ability to eliminate CRC is the establishment of a potent immunosuppressive tumor milieu by malignant cells. Since DCs are frequently defective in this milieu, the tumor setting significantly reduces the effectiveness of DC-based therapy. Determining central mechanisms contributing to tumor growth by unraveling and comprehending the interaction between CRC tumor milieu and DCs may lead to new therapeutic approaches. This study aims to review DC biology and discuss its role in T-cell-mediated anti-tumor immunity, as well as to highlight the immunosuppressive effects of the CRC tumor milieu on the function of DCs. We will also highlight the tumor microenvironment (TME)-related factors that interfere with DC function as a possible therapeutic target to enhance DC-based cell therapy efficacy.

Metabolic deficiencies underlie reduced plasmacytoid dendritic cell IFN-I production following viral infection

Type I Interferons (IFN-I) are central to host protection against viral infections, with plasmacytoid dendritic cells (pDC) being the most significant source, yet pDCs lose their IFN-I production capacity following an initial burst of IFN-I, resulting in susceptibility to secondary infections. The underlying mechanisms of these dynamics are not well understood. Here we find that viral infection reduces the capacity of pDCs to engage both oxidative and glycolytic metabolism. Mechanistically, we identify lactate dehydrogenase B (LDHB) as a positive regulator of pDC IFN-I production in mice and humans; meanwhile, LDHB deficiency is associated with suppressed IFN-I production, pDC metabolic capacity, and viral control following infection. In addition, preservation of LDHB expression is sufficient to partially retain the function of otherwise exhausted pDCs, both in vitro and in vivo. Furthermore, restoring LDHB in vivo in pDCs from infected mice increases IFNAR-dependent, infection-associated pathology. Our work thus identifies a mechanism for balancing immunity and pathology during viral infections, while also providing insight into the highly preserved infection-driven pDC inhibition.

Sustained inhibition of CSF1R signaling augments antitumor immunity through inhibiting tumor-associated macrophages

Tumor-associated macrophages (TAMs) are one of the key immunosuppressive components in the tumor microenvironment (TME) and contribute to tumor development, progression, and resistance to cancer immunotherapy. Several reagents targeting TAMs have been tested in preclinical and clinical studies, but they have had limited success. Here, we show that a unique reagent, FF-10101, exhibited a sustained inhibitory effect against colony-stimulating factor 1 receptor by forming a covalent bond and reduced immunosuppressive TAMs in the TME, which led to strong antitumor immunity. In preclinical animal models, FF-10101 treatment significantly reduced immunosuppressive TAMs and increased antitumor TAMs in the TME. In addition, tumor antigen-specific CD8+ T cells were increased; consequently, tumor growth was significantly inhibited. Moreover, combination treatment with an anti-programmed cell death 1 (anti-PD-1) antibody and FF-10101 exhibited a far stronger antitumor effect than either treatment alone. In human cancer specimens, FF-10101 treatment reduced programmed cell death 1 ligand 1 (PD-L1) expression on TAMs, as observed in animal models. Thus, FF-10101 acts as an immunomodulatory agent that can reduce immunosuppressive TAMs and augment tumor antigen-specific T cell responses, thereby generating an immunostimulatory TME. We propose that FF-10101 is a potential candidate for successful combination cancer immunotherapy with immune checkpoint inhibitors, such as PD-1/PD-L1 blockade.

The Role of Chronic Inflammation in Pediatric Cancer

Inflammation plays a crucial role in wound healing and the host immune response following pathogenic invasion. However, unresolved chronic inflammation can result in tissue fibrosis and genetic alterations that contribute to the pathogenesis of human diseases such as cancer. Recent scientific advancements exploring the underlying mechanisms of malignant cellular transformations and cancer progression have exposed significant disparities between pediatric and adult-onset cancers. For instance, pediatric cancers tend to have lower mutational burdens and arise in actively developing tissues, where cell-cycle dysregulation leads to gene, chromosomal, and fusion gene development not seen in adult-onset counterparts. As such, scientific findings in adult cancers cannot be directly applied to pediatric cancers, where unique mutations and inherent etiologies remain poorly understood. Here, we review the role of chronic inflammation in processes of genetic and chromosomal instability, the tumor microenvironment, and immune response that result in pediatric tumorigenesis transformation and explore current and developing therapeutic interventions to maintain and/or restore inflammatory homeostasis.

Dendritic cell immunometabolism - a potential therapeutic target for allergic diseases

Allergic diseases are a group of chronic inflammatory disorders driven by abnormal immune responses. Dendritic cells (DCs) play a pivotal role in the initiation and progression of allergic diseases by modulating T cell responses. Extensive progress has been made in characterizing crucial roles of metabolic reprogramming in the regulation of immune cell functions. As the critical upstream regulators and effectors in allergic responses, the activation, migration, and function of DCs are reliant on metabolic reprogramming. In this review, we summarize the metabolic characteristics of DCs, and how the cellular microenvironment shapes DC function. We also elucidate the metabolic regulation of DC biology in the context of allergic diseases and targeted therapeutic strategies based on DC metabolism regulation. Understanding the functional alterations in DCs during allergic responses and the underlying mechanisms governing its metabolic regulation is crucial for the development of effective strategies for the prevention and treatment of allergic diseases.

Gastroesophageal reflux disease increases predisposition to severe COVID-19: Insights from integrated Mendelian randomization and genetic analysis

OBJECTIVE

This study aims to investigate the potential causal relationship, shared genomic loci, as well as potential molecular pathways and tissue-specific expression patterns between gastroesophageal reflux disease (GERD) and the risk of hospitalized/severe 2019 coronavirus disease (COVID-19).

METHODS

We employed linkage disequilibrium score regression and bidirectional Mendelian randomization (MR) analysis to explore potential genetic associations between GERD (N = 602,604) and hospitalized COVID-19 (N = 2095,324) as well as severe COVID-19 (N = 1086,211). Additionally, shared genomic loci were extracted from common pivotal regions, further confirmed through corresponding colocalization analyses. GERD-driven molecular pathway network was constructed using extensive literature data mining to understand the molecular-level impacts of GERD on COVID-19.

RESULTS

Our results revealed a significant positive genetic correlation between GERD and both hospitalized (rg  =  0.418) and severe COVID-19 (rg  =  0.314). Furthermore, the MR analysis demonstrated a unidirectional causal effect of genetic predisposition to GERD on COVID-19 outcomes, including hospitalized COVID-19 (odds ratio [OR]: 1.33, 95% confidence interval [CI]: 1.27-1.44, p = 9.17e - 12) and severe COVID-19 (OR: 1.27, 95% CI: 1.18-1.37, p = 1.20e - 05). Additionally, GERD and both COVID-19 conditions shared one genomic locus with lead-SNPs rs1011407 and rs1123573, corresponding to the transcription factor BCL11A. Colocalization analysis further demonstrated a significant positive correlation between genome-wide association study and expression quantitative trait locus (eQTL) abnormalities, including rs1011407 (eQTL_p = 2.35e - 07) and rs1123573 (eQTL_p = 2.74e - 05). Molecular pathway analysis indicated that GERD might promote the progression of COVID-19 by inducting immune-activated and inflammation-related pathways.

CONCLUSION

These findings confirm that genetically determined GERD may increase the susceptibility to hospitalized/severe COVID-19. The shared genetic loci and the potential molecular pathways offer valuable insights into causal connections between GERD and COVID-19.

Myeloid cells meet CD8+ T cell exhaustion in cancer: What, why and how

Exhausted T cell (Tex) is a specific state of T cell dysfunction, in which these T cells gradually lose their effector function and change their phenotype during chronic antigen stimulation. The enrichment of exhausted CD8+ T cell (CD8+ Tex) in the tumor microenvironment is one of the important reasons leading to the poor efficacy of immunotherapy. Recent studies have reported many reasons leading to the CD8+ T cell exhaustion. In addition to cancer cells, myeloid cells can also contribute to T cell exhaustion via many ways. In this review, we discuss the history of the concept of exhaustion, CD8+ T cell dysfunction states, the heterogeneity, origin, and characteristics of CD8+ Tex. We then focus on the effects of myeloid cells on CD8+ Tex, including tumor-associated macrophages (TAMs), dendritic cells (DCs) and neutrophils. Finally, we systematically summarize current strategies and recent advancements in therapies reversing and CD8+ T cell exhaustion.

Deletion of gE in Herpes Simplex Virus 1 Leads to Increased Extracellular Virus Production and Augmented Interferon Alpha Production by Peripheral Blood Mononuclear Cells

Herpes simplex virus (HSV) in humans and pseudorabies virus (PRV) in pigs are both alphaherpesviruses. Plasmacytoid dendritic cells (pDCs) make part of the peripheral blood mononuclear cells (PBMCs) and are specialized in producing large amounts of antiviral type I interferon (IFN-I). IFN-I production by PBMCs in response to both HSV-1 and PRV can be virtually exclusively attributed to pDCs. Recently, we discovered that cells infected with gEnull PRV trigger increased production of IFNalpha by porcine PBMCs/pDCs compared with cells infected with wild-type (WT) PRV. This increased IFNalpha response correlates with increased extracellular virus production triggered by gEnull PRV compared with WT PRV. The gE protein and some of its currently described functions are conserved in different alphaherpesviruses, including PRV and HSV-1. In the current study, we report that cells infected with gEnull HSV-1 trigger increased IFNalpha production by human PBMCs and increased extracellular virus production compared with WT HSV-1. Hence, these recently described functions of PRV gE are conserved in HSV-1 gE. Since the increased extracellular virus production and IFNalpha response have also been reported for successful (gEnull) PRV vaccines, the current findings may have important consequences for the rational design of HSV vaccines.

BPDCN MYB fusions regulate cell cycle genes, impair differentiation, and induce myeloid-dendritic cell leukemia

MYB fusions are recurrently found in select cancers, including blastic plasmacytoid DC neoplasm (BPDCN), an acute leukemia with poor prognosis. They are markedly enriched in BPDCN compared with other blood cancers and, in some patients, are the only obvious somatic mutation detected. This suggests that they may alone be sufficient to drive DC transformation. MYB fusions are hypothesized to alter the normal transcription factor activity of MYB, but, mechanistically, how they promote leukemogenesis is poorly understood. Using CUT&RUN chromatin profiling, we found that, in BPDCN leukemogenesis, MYB switches from being a regulator of DC lineage genes to aberrantly regulating G2/M cell cycle control genes. MYB fusions found in patients with BPDCN increased the magnitude of DNA binding at these locations, and this was linked to BPDCN-associated gene expression changes. Furthermore, expression of MYB fusions in vivo impaired DC differentiation and induced transformation to generate a mouse model of myeloid-dendritic acute leukemia. Therapeutically, we present evidence that all-trans retinoic acid (ATRA) may cause loss of MYB protein and cell death in BPDCN.

Circulating immune landscape in melanoma patients undergoing anti-PD1 therapy reveals key immune features according to clinical response to treatment

Introduction

Immune checkpoint blockers (ICB) bring unprecedented clinical success, yet many patients endure immune mediated adverse effects and/or fail to respond. Predictive signatures of response to ICB and mechanisms of clinical efficacy or failure remain understudied. DC subsets, in network with conventional αβ T (Tconv), NK, γδ T and iNKT cells, harbor pivotal roles in tumor control, yet their involvement in response to ICB remained underexplored.

Methods

We performed an extensive longitudinal monitoring of circulating immune cells from melanoma patients treated with first-line anti-PD1, before (T0) and during treatment. We assessed the phenotypic and functional features of DC and effector cells' subsets by multi-parametric flow cytometry and ProcartaPlex® dosages.

Results

We revealed differences according to response to treatment and modulations of patterns during treatment, highlighting a strong link between the immune landscape and the outcome of anti-PD1 therapy. Responders exhibited higher frequencies of circulating cDC1s, CD8+ T cells, and γδ2+ T cells in central memory (CM) stage. Notably, we observed a distinct remodeling of ICP expression profile, activation status and natural cytotoxicity receptor patterns of immune subsets during treatment. Anti-PD1 modulated DCs' functionality and triggered deep changes in the functional orientation of Tconv and γδT cells.

Discussion

Overall, our work provides new insights into the immunological landscape sustaining favorable clinical responses or resistance to first-line anti-PD1 therapy in melanoma patients. Such exploration participates in uncovering the mechanism of action of anti-PD1, discovering innovative predictive signatures of response, and paves the way to design pertinent combination strategies to improve patient clinical benefits in the future.

Repeated CXCR4 Blockade by Plerixafor Attenuates Transplant Vasculopathy in Murine Aortic Allografts

Plerixafor, a hematopoietic stem cell mobilization agent, increases the peripheral blood content of effector and regulatory T cells and may have beneficial effects on cardiac allograft vasculopathy. The aim of the current study was to evaluate its effects in a murine aortic allograft model using different application procedures. Allogeneic donor aorta grafts (n = 8/group) from C57BL/6 mice(H2b) were abdominally transplanted into CBA mice (H2k). Plerixafor application was performed either continuously for 14 d using abdominally implanted osmotic pumps (1 mg/kg/d) or i.p. with a single dose (1 and 5 mg/kg) on day 0 or pulsed injections of 1 mg/kg on days 0, 7, 14, and 21. Cell distribution was monitored by FACS. Aortic grafts were evaluated for neointima development by Elastica-van-Gieson on day 30. Immunofluorescence and intragraft gene expression analysis were performed. On day 14, significantly fewer hematopoietic stem cells were found in the bone marrow of all plerixafor-treated mice. In the pulsed application group, significantly more hematopoietic stem cells were found in the peripheral blood on day 14 (0.045 ± 0.002%; p < 0.01 [pulsed]; versus 0.0068 ± 0.002% [control]) and also more regulatory T cells. PCR revealed lower inflammatory cytokines. The luminal occlusion was significantly reduced in the pulsed treated group (33.65 ± 8.84 versus 53.13 ± 12.41) going along with decreased neointimal CD4+ T cell and plasmacytoid dendritic cell infiltration, as well as less smooth muscle cell proliferation. The application of plerixafor attenuates chronic rejection in aortic allografts via immunomodulatory effects. Injection of repeated low-dose plerixafor is the most effective application form in the aortic transplant model.

UDP-glucose ceramide glucosyltransferase specifically upregulated in plasmacytoid dendritic cells regulates type I interferon production upon CpG stimulation

Plasmacytoid dendritic cells (pDCs) are a distinct subset of DCs involved in immune regulation and antiviral immune responses. Recent studies have elucidated the metabolic profile of pDCs and reported that perturbations in amino acid metabolism can modulate their immune functions. Glycolipid metabolism is suggested to be highly active in pDCs; however, its significance remains unclear. In this study, bulk RNA-sequencing analysis confirmed the known pDC-marker expressions, including interleukin (IL)-3R (CD123), BDCA-2 (CD303), BDCA-4 (CD304), and toll-like receptor 9, compared with that of myeloid DCs (mDCs). Among the differentially expressed genes, UDP-glucose-ceramide glucosyltransferase (UGCG) expression was significantly upregulated in pDCs than in mDCs. Moreover, pDC-specific UGCG expression was observed at both the mRNA and protein levels in pDCs and pDC-like cell lines, including CAL-1 and PMDC05 cell lines. Pharmacological or clustered regularly interspaced palindromic repeat (CRISPR)/CRISPR-associated protein 9-mediated genetic inhibition of UGCG did not affect the pDC phenotype as evidenced by the persistent expression of IL-3R and BDCA-2 in pDC-like cell lines. However, UGCG knockout resulted in reduced type I interferon production in pDCs upon CpG activation. In addition, UGCG-knockout pDC-like cell lines exhibited reduced transduction by vesicular stomatitis virus-G pseudo-typed lentiviral vectors, suggesting that low UGCG expression hinders infectivity. Collectively, our findings suggest that pDC-specific UGCG expression is critical for cytokine production and antiviral immune responses in pDCs.

Human CD34+-derived plasmacytoid dendritic cells as surrogates for primary pDCs and potential cancer immunotherapy

Introduction

Plasmacytoid dendritic cells (pDCs) are capable of triggering broad immune responses, yet, their scarcity in blood coupled to their reduced functionality in cancer, makes their therapeutic use for in situ activation or vaccination challenging.

Methods

We designed an in vitro differentiation protocol tailored for human pDCs from cord blood (CB) hematopoietic stem cells (HSCs) with StemRegenin 1 (SR-1) and GM-CSF supplementation. Next, we evaluated the identity and function of CB-pDCs compared to human primary pDCs. Furthermore, we tested the potential of CB-pDCs to support anti-tumor immune responses in co-culture with tumor explants from CRC patients.

Results

Here, we report an in vitro differentiation protocol enabling the generation of 200 pDCs per HSC and highlight the role of GM-CSF and SR-1 in CB-pDC differentiation and function. CB-pDCs exhibited a robust resemblance to primary pDCs phenotypically and functionally. Transcriptomic analysis confirmed strong homology at both, baseline and upon TLR9 or TLR7 stimulation. Further, we could confirm the potential of CB-pDCs to promote inflammation in the tumor microenvironment by eliciting cytokines associated with NK and T cell recruitment and function upon TLR7 stimulation ex vivo in patient tumor explants.

Discussion

This study highlights CB-pDCs as surrogates for primary pDCs to investigate their biology and for their potential use as cell therapy in cancer.

Phenotype of bovine mononuclear phagocytes- An update

Studying mononuclear phagocytes by flow cytometry is challenging due to their phenotypic similarities and the high plasticity of monocytic cells. Despite these challenges, significant progress has been made in cattle research through multicolor flow cytometry, transcriptomics of sorted subsets, and single-cell RNA-sequencing. Here, we provide an overview of established and proposed phenotypic classifications in the bovine mononuclear phagocyte system and discuss the challenges of marker discovery.

Immune signature of patients with cardiovascular disease predicts increased risk for a severe course of COVID-19

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection can lead to life-threatening clinical manifestations. Patients with cardiovascular disease (CVD) are at higher risk for severe courses of COVID-19. So far, however, there are hardly any strategies for predicting the course of SARS-CoV-2 infection in CVD patients at hospital admission. Thus, we investigated whether this prediction is achievable by prospectively analysing the blood immunophenotype of 94 nonvaccinated participants, including uninfected and acutely SARS-CoV-2-infected CVD patients and healthy donors, using a 36-colour spectral flow cytometry panel. Unsupervised data analysis revealed little differences between healthy donors and CVD patients, whereas the distribution of the cell populations changed dramatically in SARS-CoV-2-infected CVD patients. The latter had more mature NK cells, activated monocyte subsets, central memory CD4+ T cells, and plasmablasts but fewer dendritic cells, CD16+ monocytes, innate lymphoid cells, and CD8+ T-cell subsets. Moreover, we identified an immune signature characterised by CD161+ T cells, intermediate effector CD8+ T cells, and natural killer T (NKT) cells that is predictive for CVD patients with a severe course of COVID-19. Thus, intensified immunophenotype analyses can help identify patients at risk of severe COVID-19 at hospital admission, improving clinical outcomes through specific treatment.

The role of DC subgroups in the pathogenesis of asthma

Dendritic cells (DCs), specialized antigen-presenting cells of the immune system, act as immunomodulators in diseases of the immune system, including asthma. The understanding of DC biology has evolved over the years to include multiple subsets of DCs with distinct functions in the initiation and maintenance of asthma. Moreover, most strategies for treating asthma with relevant therapeutic agents that target DCs have been initiated from the study of DC function. We discussed the pathogenesis of asthma (including T2-high and T2-low), the roles played by different DC subpopulations in the pathogenesis of asthma, and the therapeutic strategies centered around DCs. This study will provide a scientific theoretical basis for current asthma treatment, provide theoretical guidance and research ideas for developing and studying therapeutic drugs targeting DC, and provide more therapeutic options for the patient population with poorly controlled asthma symptoms.

Engineering dendritic cell biomimetic membrane as a delivery system for tumor targeted therapy

Targeted immunotherapies make substantial strides in clinical cancer care due to their ability to counteract the tumor's capacity to suppress immune responses. Advances in biomimetic technology with minimally immunogenic and highly targeted, are addressing issues of targeted drug delivery and disrupting the tumor's immunosuppressive environment to trigger immune activation. Specifically, the use of dendritic cell (DC) membranes to coat nanoparticles ensures targeted delivery due to DC's unique ability to activate naive T cells, spotlighting their role in immunotherapy aimed at disrupting the tumor microenvironment. The potential of DC's biomimetic membrane to mediate immune activation and target tumors is gaining momentum, enhancing the effectiveness of cancer treatments in conjunction with other immune responses. This review delves into the methodologies behind crafting DC membranes and the fusion of dendritic and tumor cell membranes for encapsulating therapeutic nanoparticles. It explores their applications and recent advancements in combating cancer, offering an all-encompassing perspective on DC biomimetic nanosystems, immunotherapy driven by antigen presentation, and the collaborative efforts of drug delivery in chemotherapy and photodynamic therapies. Current evidence shows promise in augmenting combined therapeutic approaches for cancer treatment and holds translational potential for various cancer treatments in a clinical setting.

The Absence of Thyroid-Stimulating Hormone Receptor Expression on Natural Killer T Cells: Implications for the Immune-Endocrine Interaction

The expression of thyroid-stimulating hormone receptor (TSHR) has been documented on various immune cells, including B lymphocytes, T lymphocytes, Natural Killer (NK) cells, monocytes, and dendritic cells (DCs). Natural Killer T (NKT) cells serve as a crucial link between innate and adaptive immunity, playing significant roles in immunological interactions and autoimmune diseases. The aim of the present study was to evaluate the presence of TSHR on NKT cells. Our research involved patients with thyroid disease, as well as healthy controls. Peripheral blood mononuclear cells (PBMCs) and, thereafter, NKT cells were isolated from 86 patients with benign nodular thyroid disease with and without autoimmune thyroid disease (AITD) (28 and 56 cases, respectively), and TSHR expression was analyzed using fluorescence-activated cell sorting (FACS). In order to confirm the results, the reverse-transcription polymerase chain reaction (RT-PCR) method was used in cells obtained from healthy individuals. Our findings obtained with application of the FACS method revealed that TSHR is not expressed on NKT cells in either AITD or non-AITD patients, though TSHR was detected in the total PBMC population (TSHR+ cells 2.77%). The absence of TSHR on NKT cells was further confirmed with RT-PCR in healthy individuals (p < 0.0001). These results questioned the previously suggested direct influence of NKT cells on AITD development.

Causal association of immune cells and endometritis: a Mendelian randomization study

Research exploring the link between immune cell profiles and the development of endometritis remains scant. This gap necessitates further study to decode the complex interrelations influencing this condition. In this analysis, we leveraged two-sample Mendelian randomization to examine the causal ties between the phenotypes of immune cells and the incidence of endometritis. Our evaluation hinged on data from 3757 participants hailing from Sardinia, focusing on a diverse array of 731 immune phenotypes, and cross-referenced with endometritis data sourced from the UK Biobank. To ensure rigor, we performed sensitivity analyses, utilized MR-Egger and MR-Presso to check for pleiotropy, and applied Cochran's Q test for assessing the heterogeneity of our findings. Our investigation identified numerous immune characteristics associated with endometritis. For certain immune traits, a lower risk of endometritis was observed, including: Absolute Counts of CD39 + CD4 + T cells, CD25 + CD39 + CD4 regulatory T cells, and CD25 + + CD8 + T cells; Absolute Counts of Switched Memory B cells; CD19 expression on IgD + CD38dim and Switched Memory B cells; CD20 expression on IgD + CD38- Unswitched Memory B cells; percentage of Switched Memory B cells among lymphocytes; CD16-CD56 expression on HLA DR + Natural Killer cells; percentage of CD11c + CD62L- monocytes; CD86 expression on monocytes; CCR2 expression on CD14 + CD16 + monocytes; and CD14 expression on Monocytic Myeloid-Derived Suppressor Cells, with Odds Ratios (ORs) between 0.413 and 0.703. On the contrary, increased risks of endometritis were linked with: the percentage of Effector Memory CD4 + T cells within the CD4 + T cell population; percentages of HLA DR + T cells and HLA DR + CD8 + T cells among T cells; CD4 expression on CD28 + CD4 + T cells; CD20 expression on CD20- CD38- B cells; percentage of IgD + CD24 + B cells within the B cell population; CD62L expression on CD62L + myeloid Dendritic Cells; and Absolute Counts of Plasmacytoid Dendritic Cells, with ORs from 1.473 to 2.677, indicating these traits potentially elevate the risk of developing endometritis. Our research delineates distinct causal links between specific immune cell phenotypes and endometritis, offering new perspectives that could contribute to the pinpointing of new therapeutic avenues for this condition.

The role of dendritic cells in tertiary lymphoid structures: implications in cancer and autoimmune diseases

Tertiary Lymphoid Structures (TLS) are organized aggregates of immune cells such as T cells, B cells, and Dendritic Cells (DCs), as well as fibroblasts, formed postnatally in response to signals from cytokines and chemokines. Central to the function of TLS are DCs, professional antigen-presenting cells (APCs) that coordinate the adaptive immune response, and which can be classified into different subsets, with specific functions, and markers. In this article, we review current data on the contribution of different DC subsets to TLS function in cancer and autoimmunity, two opposite sides of the immune response. Different DC subsets can be found in different tumor types, correlating with cancer prognosis. Moreover, DCs are also present in TLS found in autoimmune and inflammatory conditions, contributing to disease development. Broadly, the presence of DCs in TLS appears to be associated with favorable clinical outcomes in cancer while in autoimmune pathologies these cells are associated with unfavorable prognosis. Therefore, it is important to analyze the complex functions of DCs within TLS in order to enhance our fundamental understanding of immune regulation but also as a possible route to create innovative clinical interventions designed for the specific needs of patients with diverse pathological diseases.

The role of interferon signaling in neurodegeneration and neuropsychiatric disorders

Recent advances in transcriptomics research have uncovered heightened interferon (IFN) responses in neurodegenerative diseases including Alzheimer's disease, primary tauopathy, Parkinson's disease, TDP-43 proteinopathy, and related mouse models. Augmented IFN signaling is now relatively well established for microglia in these contexts, but emerging work has highlighted a novel role for IFN-responsive T cells in the brain and peripheral blood in some types of neurodegeneration. These findings complement a body of literature implicating dysregulated IFN signaling in neuropsychiatric disorders including major depression and post-traumatic stress disorder. In this review, we will characterize and integrate advances in our understanding of IFN responses in neurodegenerative and neuropsychiatric disease, discuss how sex and ancestry modulate the IFN response, and examine potential mechanistic explanations for the upregulation of antiviral-like IFN signaling pathways in these seemingly non-viral neurological and psychiatric disorders.

Analysis of the heterogeneity and complexity of murine extraorbital lacrimal gland via single-cell RNA sequencing

PURPOSE

The lacrimal gland is essential for maintaining ocular surface health and avoiding external damage by secreting an aqueous layer of the tear film. However, a healthy lacrimal gland's inventory of cell types and heterogeneity remains understudied.

METHODS

Here, 10X Genome-based single-cell RNA sequencing was used to generate an unbiased classification of cellular diversity in the extraorbital lacrimal gland (ELG) of C57BL/6J mice. From 43,850 high-quality cells, we produced an atlas of cell heterogeneity and defined cell types using classic marker genes. The possible functions of these cells were analyzed through bioinformatics analysis. Additionally, the CellChat was employed for a preliminary analysis of the cell-cell communication network in the ELG.

RESULTS

Over 37 subclasses of cells were identified, including seven types of glandular epithelial cells, three types of fibroblasts, ten types of myeloid-derived immune cells, at least eleven types of lymphoid-derived immune cells, and five types of vascular-associated cell subsets. The cell-cell communication network analysis revealed that fibroblasts and immune cells play a pivotal role in the dense intercellular communication network within the mouse ELG.

CONCLUSIONS

This study provides a comprehensive transcriptome atlas and related database of the mouse ELG.

A genome-wide association study identified PTPN2 as a population-specific susceptibility gene locus for primary biliary cholangitis

BACKGROUND AND AIMS

Previous genome-wide association studies (GWAS) have indicated the involvement of shared (population-nonspecific) and nonshared (population-specific) susceptibility genes in the pathogenesis of primary biliary cholangitis (PBC) among European and East-Asian populations. Although a meta-analysis of these distinct populations has recently identified more than 20 novel PBC susceptibility loci, analyses of population-specific genetic architecture are still needed for a more comprehensive search for genetic factors in PBC.

APPROACH AND RESULTS

Protein tyrosine phosphatase nonreceptor type 2 ( PTPN2) was identified as a novel PBC susceptibility gene locus through GWAS and subsequent genome-wide meta-analysis involving 2181 cases and 2699 controls from the Japanese population (GWAS-lead variant: rs8098858, p = 2.6 × 10 -8 ). In silico and in vitro functional analyses indicated that the risk allele of rs2292758, which is a primary functional variant, decreases PTPN2 expression by disrupting Sp1 binding to the PTPN2 promoter in T follicular helper cells and plasmacytoid dendritic cells. Infiltration of PTPN2-positive T-cells and plasmacytoid dendritic cells was confirmed in the portal area of the PBC liver by immunohistochemistry. Furthermore, transcriptomic analysis of PBC-liver samples indicated the presence of a compromised negative feedback loop in vivo between PTPN2 and IFNG in patients carrying the risk allele of rs2292758.

CONCLUSIONS

PTPN2 , a novel susceptibility gene for PBC in the Japanese population, may be involved in the pathogenesis of PBC through an insufficient negative feedback loop caused by the risk allele of rs2292758 in IFN-γ signaling. This suggests that PTPN2 could be a potential molecular target for PBC treatment.

The roles of the kynurenine pathway in COVID-19 neuropathogenesis

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the highly contagious respiratory disease Corona Virus Disease 2019 (COVID-19) that may lead to various neurological and psychological disorders that can be acute, lasting days to weeks or months and possibly longer. The latter is known as long-COVID or more recently post-acute sequelae of COVID (PASC). During acute COVID-19 infection, a strong inflammatory response, known as the cytokine storm, occurs in some patients. The levels of interferon-γ (IFN-γ), interferon-β (IFN-β), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) are particularly increased. These cytokines are known to activate the enzyme indoleamine 2,3-dioxygenase 1 (IDO-1), catalysing the first step of tryptophan (Trp) catabolism through the kynurenine pathway (KP) leading to the production of several neurotoxic and immunosuppressive metabolites. There is already data showing elevation in KP metabolites both acutely and in PASC, especially regarding cognitive impairment. Thus, it is likely that KP involvement is significant in SARS-CoV-2 pathogenesis especially neurologically.

Boosting immunotherapy efficacy: Empowering the Potency of Dendritic cells loaded with breast cancer lysates through CTLA-4 suppression

Anticancer immunotherapies with a dendritic Cell (DC) basis are becoming more popular. However, it has been suggested that the tumor's immunosuppressive mechanisms, such as inhibitory immunological checkpoint molecules, reduce the effectiveness of anticancer immunogenicity mediated by DC. Thus, overcoming immune checkpoints and inducing effective antigen-specific T-cell responses uniquely produced with malignant cells represent the key challenges. Among the inhibitory immune checkpoints, DCs' ability to mature and present antigens is decreased by CTLA-4 expression. Consequently, we hypothesized that by expressing CTLA-4 cells on DCs, the T cells' activation against tumor antigens would be suppressed when confronted with these antigens presented by DCs. In this research, by loading cell lysate of breast cancer (BC) on DCs and the other hand by inhibiting the induction of CTLA-4 using small interfering RNA (siRNA), we assessed the functional activities and phenotypes of DCs, and also the responses associated with T-cells following co-culture DC/T cell. Our research has shown that the suppression of CTLA-4 enhanced the stimulating capabilities of DCs. Additionally, CTLA-4-suppressed BC cell lysate-loaded DCs produced more IL-4 and IFN-ϒ and increased T cell induction in contrast to DCs without CTLA-4 suppression. Together, our data point to CTLA-4-suppressed DCs loaded with BC cell lysate as a potentially effective treatment method. However, further research is required before employing this method in therapeutic contexts.

Profound deficiencies in mature blood and bone marrow progenitor dendritic cells in Chronic Lymphocyticcytic Leukemia patients

Chronic lymphocytic leukemia (CLL) patients are immunocompromised and highly vulnerable to serious recurrent infections. Conventional dendritic cells (cDCs) and plasmacytoid DCs (pDCs) are principal sensors of infection and are essential in orchestrating innate and adaptive immune responses to resolve infection. This study identified significant deficiencies in six functionally distinct DC subsets in blood of untreated CLL (UT-CLL) patients and selective normalization of pDCs in response to acalabrutinib (a Bruton tyrosine kinase inhibitor) therapy. DCs are continuously replenished from hematopoiesis in bone marrow (BM). Four BM developmental intermediates that give rise to cDCs and pDCs were examined and significant reductions of these were identified in UT-CLL patients supporting a precursor/progeny relationship. The deficiencies in blood DCs and BM DC progenitors were significantly associated with alterations in the Flt3/FL signaling pathway critical to DC development and function. Regarding clinical parameter, cDC subset deficiencies are associated with adverse prognostic indicators of disease progression, including IGHV mutation, CD49d, CD38, and ZAP-70 status. Importantly, UT-CLL patients with shared DC subset deficiencies had shorter time-to-first treatment (TTFT), uncovering a profound alteration in innate immunity with the potential to instruct therapeutic decision-making.

Immunometabolic characteristics of Dendritic Cells and its significant modulation by mitochondria-associated signaling in the tumor microenvironment influence cancer progression

Dendritic cells (DCs) mediated T-cell responses is critical to anti-tumor immunity. This study explores immunometabolic attributes of DC, emphasizing on mitochondrial association, in Tumor Microenvironment (TME) that regulate cancer progression. Conventional DC subtypes cross-present tumor-associated antigens to activate lymphocytes. However, plasmacytoid DCs participate in both pro- and anti-tumor signaling where mitochondrial reactive oxygen species (mtROS) play crucial role. CTLA-4, CD-47 and other surface-receptors of DC negatively regulates T-cell. Increased glycolysis-mediated mitochondrial citrate buildup and translocation to cytosol with augmented NADPH, enhances mitochondrial fatty acid synthesis fueling DCs. Different DC subtypes and stages, exhibit variable mitochondrial content, membrane potential, structural dynamics and bioenergetic metabolism regulated by various cytokine stimulation, e.g., GM-CSF, IL-4, etc. CD8α+ cDC1s augmented oxidative phosphorylation (OXPHOS) which diminishes at advance effector stages. Glutaminolysis in mitochondria supplement energy in DCs but production of kynurenine and other oncometabolites leads to immunosuppression. Mitochondria-associated DAMPs cause activation of cGAS-STING pathway and inflammasome oligomerization stimulating DC and T cells. In this study, through a comprehensive survey and critical analysis of the latest literature, the potential of DC metabolism for more effective tumor therapy is highlighted. This underscores the need for future research to explore specific therapeutic targets and potential drug candidates.

Single-cell transcriptomic analysis identifies infiltrating plasmacytoid dendritic cells in psoriasis epidermis

Our study unveils the cellular and molecular dynamics in psoriasis epidermis, revealing diverse cell states and their interactions driving inflammation and altered developmental trajectories. Importantly, a previously overlooked plasmacytoid dendritic cell cluster with inflammatory properties was identified in the epidermis of chronic psoriasis lesions, suggesting a potential role for these cells in chronic psoriasis.

Causal pathways in lymphoid leukemia: the gut microbiota, immune cells, and serum metabolites

Background

We employed Mendelian randomization (MR) to investigate the causal relationship between the gut microbiota and lymphoid leukemia, further exploring the causal relationships among immune cells, lymphoid leukemia, and potential metabolic mediators.

Methods

We utilized data from the largest genome-wide association studies to date, encompassing 418 species of gut microbiota, 713 types of immune cells, and 1,400 serum metabolites as exposures. Summary statistics for lymphoid leukemia, acute lymphocytic leukemia (ALL), and chronic lymphocytic leukemia (CLL) were obtained from the FinnGen database. We performed bidirectional Mendelian analyses to explore the causal relationships among the gut microbiota, immune cells, serum metabolites, and lymphoid leukemia. Additionally, we conducted a two-step mediation analysis to identify potential intermediary metabolites between immune cells and lymphoid leukemia.

Results

Several gut microbiota were found to have causal relationships with lymphoid leukemia, ALL, and CLL, particularly within the Firmicutes and Bacteroidetes phyla. In the two-step MR analysis, various steroid hormone metabolites (such as DHEAS, pregnenolone sulfateprogestogen derivatives, and androstenediol-related compounds) were identified as potential intermediary metabolites between lymphoid leukemia and immune cells. In ALL, the causal relationship between 1-palmitoyl-2-docosahexaenoyl-GPE (16:0/22:6) and ALL was mediated by CD62L-plasmacytoid DC%DC (mediated proportion=-2.84%, P=0.020). In CLL, the causal relationship between N6,n6,n6-trimethyllysine and CLL was mediated by HLA DR+ CD8br AC (mediated proportion=4.07%, P=0.021).

Conclusion

This MR study provides evidence supporting specific causal relationships between the gut microbiota and lymphoid leukemia, as well as between certain immune cells and lymphoid leukemia with potential intermediary metabolites.

Research Progress on Dendritic Cells in Hepatocellular Carcinoma Immune Microenvironments

Dendritic cells (DCs) are antigen-presenting cells that play a crucial role in initiating immune responses by cross-presenting relevant antigens to initial T cells. The activation of DCs is a crucial step in inducing anti-tumor immunity. Upon recognition and uptake of tumor antigens, activated DCs present these antigens to naive T cells, thereby stimulating T cell-mediated immune responses and enhancing their ability to attack tumors. It is particularly noted that DCs are able to cross-present foreign antigens to major histocompatibility complex class I (MHC-I) molecules, prompting CD8+ T cells to proliferate and differentiate into cytotoxic T cells. In the malignant progression of hepatocellular carcinoma (HCC), the inactivation of DCs plays an important role, and the activation of DCs is particularly important in anti-HCC immunotherapy. In this review, we summarize the mechanisms of DCs activation in HCC, the involved regulatory factors and strategies to activate DCs in HCC immunotherapy. It provides a basis for the study of HCC immunotherapy through DCs activation.

Preexisting Skin-Resident CD8 and γδ T-cell Circuits Mediate Immune Response in Merkel Cell Carcinoma and Predict Immunotherapy Efficacy

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer with a ∼50% response rate to immune checkpoint blockade (ICB) therapy. To identify predictive biomarkers, we integrated bulk and single-cell RNA sequencing (RNA-seq) with spatial transcriptomics from a cohort of 186 samples from 116 patients, including bulk RNA-seq from 14 matched pairs pre- and post-ICB. In nonresponders, tumors show evidence of increased tumor proliferation, neuronal stem cell markers, and IL1. Responders have increased type I/II interferons and preexisting tissue resident (Trm) CD8 or Vδ1 γδ T cells that functionally converge with overlapping antigen-specific transcriptional programs and clonal expansion of public T-cell receptors. Spatial transcriptomics demonstrated colocalization of T cells with B and dendritic cells, which supply chemokines and costimulation. Lastly, ICB significantly increased clonal expansion or recruitment of Trm and Vδ1 cells in tumors specifically in responders, underscoring their therapeutic importance. These data identify potential clinically actionable biomarkers and therapeutic targets for MCC. Significance: MCC serves as a model of ICB response. We utilized the largest-to-date, multimodal MCC dataset (n = 116 patients) to uncover unique tumor-intrinsic properties and immune circuits that predict response. We identified CD8 Trm and Vδ1 T cells as clinically actionable mediators of ICB response in major histocompatibility complex-high and -low MCCs, respectively.

TICRR Overexpression Enhances Disease Aggressiveness and Immune Infiltration of Cutaneous Melanoma

Objective

To investigate the role of the TopBP1 interacting checkpoint and replication regulator (TICRR) in cutaneous melanoma (CM) as a prognostic biomarker and therapeutic target.

Methods

TICRR expression in tumour samples was explored using the TCGA and the GTEx database. The Kaplan-Meier survival curve, nomogram model and risk score curve were established to evaluate the prognostic role of TICRR in CM. Tissue samples of CM patients were obtained to validate the TICRR expression further. Several experiments in vitro were conducted to investigate the effect of TICRR upon CM aggressiveness and to explore underlying mechanisms.

Results

TICRR was overexpressed in CM tissue and was correlated with poor prognosis of CM patients. The knockdown of TICRR decreased the proliferation, migration, and invasion of CM cells, whereas overexpression produced the opposite effect. Furthermore, TICRR suppression substantially attenuated the activation of PI3K/AKT/mTOR signalling, while the PI3K/AKT inhibitor LY294002 could partially reverse the aggressiveness-enhancing effect induced by TICRR overexpression. It was further confirmed that TICRR was closely related to immune cell infiltration activities by using immune infiltration and immunofluorescence analysis.

Conclusion

TICRR overexpression may enhance CM aggressiveness by activating the PI3K/Akt/mTOR pathway and promoting immune infiltration. TICRR was verified as a potential prognostic biomarker and therapeutic target for CM.

The role of plasmacytoid dendritic cells (pDCs) in immunity during viral infections and beyond

Type I and III interferons (IFNs) are essential for antiviral immunity and act through two different but complimentary pathways. First, IFNs activate intracellular antimicrobial programs by triggering the upregulation of a broad repertoire of viral restriction factors. Second, IFNs activate innate and adaptive immunity. Dysregulation of IFN production can lead to severe immune system dysfunction. It is thus crucial to identify and characterize the cellular sources of IFNs, their effects, and their regulation to promote their beneficial effects and limit their detrimental effects, which can depend on the nature of the infected or diseased tissues, as we will discuss. Plasmacytoid dendritic cells (pDCs) can produce large amounts of all IFN subtypes during viral infection. pDCs are resistant to infection by many different viruses, thus inhibiting the immune evasion mechanisms of viruses that target IFN production or their downstream responses. Therefore, pDCs are considered essential for the control of viral infections and the establishment of protective immunity. A thorough bibliographical survey showed that, in most viral infections, despite being major IFN producers, pDCs are actually dispensable for host resistance, which is achieved by multiple IFN sources depending on the tissue. Moreover, primary innate and adaptive antiviral immune responses are only transiently affected in the absence of pDCs. More surprisingly, pDCs and their IFNs can be detrimental in some viral infections or autoimmune diseases. This makes the conservation of pDCs during vertebrate evolution an enigma and thus raises outstanding questions about their role not only in viral infections but also in other diseases and under physiological conditions.

BootCellNet, a resampling-based procedure, promotes unsupervised identification of cell populations via robust inference of gene regulatory networks

Recent advances in measurement technologies, particularly single-cell RNA sequencing (scRNA-seq), have revolutionized our ability to acquire large amounts of omics-level data on cellular states. As measurement techniques evolve, there has been an increasing need for data analysis methodologies, especially those focused on cell-type identification and inference of gene regulatory networks (GRNs). We have developed a new method named BootCellNet, which employs smoothing and resampling to infer GRNs. Using the inferred GRNs, BootCellNet further infers the minimum dominating set (MDS), a set of genes that determines the dynamics of the entire network. We have demonstrated that BootCellNet robustly infers GRNs and their MDSs from scRNA-seq data and facilitates unsupervised identification of cell clusters using scRNA-seq datasets of peripheral blood mononuclear cells and hematopoiesis. It has also identified COVID-19 patient-specific cells and their potential regulatory transcription factors. BootCellNet not only identifies cell types in an unsupervised and explainable way but also provides insights into the characteristics of identified cell types through the inference of GRNs and MDS.

Dendritic cells in food allergy, treatment, and tolerance

Food allergy is a growing problem with limited treatment options. It is important to understand the mechanisms of food tolerance and allergy to promote the development of directed therapies. Dendritic cells (DCs) are specialized antigen-presenting cells (APCs) that prime adaptive immune responses, such as those involved in the development of oral tolerance and food allergies. The DC subsets in the gut and skin are defined by their surface markers and function. The default response to an ingested innocuous antigen is oral tolerance, which requires either gut DCs or a subset of newly identified RORγt+ APCs to induce the development of gut peripheral regulatory T cells. However, DCs in the skin, gut, and lung can also promote allergic sensitization when they are activated under certain inflammatory conditions, such as with alarmin release or gut dysbiosis. DCs also play a role in the responses to the various modalities of food immunotherapy. Langerhans cells in the skin appear to be necessary for the response to epicutaneous immunotherapy. It will be important to determine which real-world stimuli activate the DCs that prime allergic sensitization and discover methods to selectively initiate a tolerogenic program in APCs.

Identification of diagnostic signature and immune microenvironment subtypes of venous thromboembolism

The close link between immune and pathogenesis of venous thromboembolism (VTE) has been recognized, but not fully elucidated. The current study was designed to identify immune microenvironment related signature and subtypes using explainable machine learning in VTE. We first observed an alteration of immune microenvironment in VTE patients and identified eight key immune cells involved in VTE. Then PTPN6, ITGB2, CR2, FPR2, MMP9 and ISG15 were determined as key immune microenvironment-related genes, which could divide VTE patients into two subtypes with different immune and metabolic characteristics. Also, we found that prunetin and torin-2 may be most promising to treat VTE patients in Cluster 1 and 2, respectively. By comparing six machine learning models in both training and external validation sets, XGboost was identified as the best one to predict the risk of VTE, followed by the interpretation of each immune microenvironment-related gene contributing to the model. Moreover, CR2 and FPR2 had high accuracy in distinguishing VTE and control, which may act as diagnostic biomarkers of VTE, and their expressions were validated by qPCR. Collectively, immune microenvironment related PTPN6, ITGB2, CR2, FPR2, MMP9 and ISG15 are key genes involved in the pathogenesis of VTE. The VTE risk prediction model and immune microenvironment subtypes based on those genes might benefit prevention, diagnosis, and the individualized treatment strategy in clinical practice of VTE.

Repression of SMAD3 by STAT3 and c-Ski induces conventional dendritic cell differentiation

A pleiotropic immunoregulatory cytokine, TGF-β, signals via the receptor-regulated SMADs: SMAD2 and SMAD3, which are constitutively expressed in normal cells. Here, we show that selective repression of SMAD3 induces cDC differentiation from the CD115+ common DC progenitor (CDP). SMAD3 was expressed in haematopoietic cells including the macrophage DC progenitor. However, SMAD3 was specifically down-regulated in CD115+ CDPs, SiglecH- pre-DCs, and cDCs, whereas SMAD2 remained constitutive. SMAD3-deficient mice showed a significant increase in cDCs, SiglecH- pre-DCs, and CD115+ CDPs compared with the littermate control. SMAD3 repressed the mRNA expression of FLT3 and the cDC-related genes: IRF4 and ID2. We found that one of the SMAD transcriptional corepressors, c-SKI, cooperated with phosphorylated STAT3 at Y705 and S727 to repress the transcription of SMAD3 to induce cDC differentiation. These data indicate that STAT3 and c-Ski induce cDC differentiation by repressing SMAD3: the repressor of the cDC-related genes during the developmental stage between the macrophage DC progenitor and CD115+ CDP.

Path analysis of COVID-19 cognition, social support, and mental health of pregnant women with interventional prenatal diagnosis during the COVID-19 pandemic based on structural equation modeling

This study aims to investigate the relationship between Corona Virus Disease 2019 (COVID-19) cognition, social support, and mental health among pregnant women proposed for undergoing interventional prenatal diagnosis in Sichuan Province during the COVID-19 pandemic. A total of 2270 pregnant women (2232 valid) who were proposed to undergo interventional prenatal diagnosis at a tertiary hospital prenatal diagnosis center in Sichuan Province from January to December 2022 were selected by Convenience sampling and surveyed using a self-administered general information questionnaire, social support rating scale, mental health questionnaire (including: Self-Rating Anxiety Scale, Self-Rating Depression Scale), and self-administered COVID-19 cognition questionnaire. Structural equation modeling showed that social support negatively predicted anxiety (β = -0.34, t = -14.98, P < .001) and negatively predicted depressive status (β = -0.21, t = -9.57, P < .001); COVID-19 cognition negatively predicted anxiety (β = -0.76, t = -5.34, P < .001) and depression (β = -0.40, t = -2.99, P < .01); anxiety positively predicted anxiety (β = 0.73, t = 37.34, P < .001). The overall knowledge rate of COVID-19 cognition among 2232 pregnant women who were to undergo interventional prenatal diagnosis was 76.40%. The fit indices of the model were: CMIN/DF = 3.071, GFI = 0.999, AGFI = 0.993, CFI = 0.999, RMSEA = 0.030, NFI = 0.998, and TLI = 0.992, indicating that the model had a good fit and the model was scientifically valid. Pregnant women in Sichuan province who are to undergo prenatal interventional diagnosis have a medium level of COVID-19 awareness, and their level of COVID-19 awareness and social support will directly affect their anxiety and depression level, and their anxiety level will also affect their depression level. We should give more attention to pregnant women, especially those in particular situations such as advanced age, poor maternal history, family history of genetic disease, etc, they should be given adequate care and social support, and multiple channels and types of health education should be provided for the COVID-19 to improve the pregnant women's knowledge of COVID-19, which is important for improving the mental health of pregnant women.

Transcriptional programming mediated by the histone demethylase KDM5C regulates dendritic cell population heterogeneity and function

Functional and phenotypic heterogeneity of dendritic cells (DCs) play crucial roles in facilitating the development of diverse immune responses essential for host protection. Here, we report that KDM5C, a histone lysine demethylase, regulates conventional or classical DC (cDC) and plasmacytoid DC (pDC) population heterogeneity and function. Mice deficient in KDM5C in DCs have increased proportions of cDC2Bs and cDC1s, which is partly dependent on type I interferon (IFN) and pDCs. Loss of KDM5C results in an increase in Ly6C- pDCs, which, compared to Ly6C+ pDCs, have limited ability to produce type I IFN and more efficiently stimulate antigen-specific CD8 T cells. KDM5C-deficient DCs have increased expression of inflammatory genes, altered expression of lineage-specific genes, and decreased function. In response to Listeria infection, KDM5C-deficient mice mount reduced CD8 T cell responses due to decreased antigen presentation by cDC1s. Thus, KDM5C is a key regulator of DC heterogeneity and critical driver of the functional properties of DCs.

The current role of dendritic cells in the progression and treatment of colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related deaths worldwide. Dendritic cells (DCs) constitute a heterogeneous group of antigen-presenting cells that are important for initiating and regulating both innate and adaptive immune responses. As a crucial component of the immune system, DCs have a pivotal role in the pathogenesis and clinical treatment of CRC. DCs cross-present tumor-related antigens to activate T cells and trigger an antitumor immune response. However, the antitumor immune function of DCs is impaired and immune tolerance is promoted due to the presence of the tumor microenvironment. This review systematically elucidates the specific characteristics and functions of different DC subsets, as well as the role that DCs play in the immune response and tolerance within the CRC microenvironment. Moreover, how DCs contribute to the progression of CRC and potential therapies to enhance antitumor immunity on the basis of existing data are also discussed, which will provide new perspectives and approaches for immunotherapy in patients with CRC.

Stiffness regulates dendritic cell and macrophage subtype development and increased stiffness induces a tumor-associated macrophage phenotype in cancer co-cultures

Mechanical properties of tissues including their stiffness change throughout our lives, during both healthy development but also during chronic diseases like cancer. How changes to stiffness, occurring during cancer progression, impact leukocytes is unknown. To address this, myeloid phenotypes resulting from mono- and cancer co-cultures of primary murine and human myeloid cells on 2D and 3D hydrogels with varying stiffnesses were analyzed. On soft hydrogels, conventional DCs (cDCs) developed, whereas on stiff hydrogels plasmacytoid DCs (pDCs) developed. Soft substrates promoted T cell proliferation and activation, while phagocytosis was increased on stiffer substrates. Cell populations expressing macrophage markers CD14, Ly6C, and CD16 also increased on stiff hydrogels. In cancer co-cultures, CD86+ populations decreased on higher stiffnesses across four different cancer types. High stiffness also led to increased vascular endothelial growth factor A (VEGFA), matrix metalloproteinases (MMP) and CD206 expression; 'M2' markers expressed by tumor-associated macrophages (TAMs). Indeed, the majority of CD11c+ cells expressed CD206 across human cancer models. Targeting the PI3K/Akt pathway led to a decrease in CD206+ cells in murine cultures only, while human CD86+ cells increased. Increased stiffness in cancer could, thus, lead to the dysregulation of infiltrating myeloid cells and shift their phenotypes towards a M2-like TAM phenotype, thereby actively enabling tumor progression. Additionally, stiffness-dependent intracellular signaling appears extremely cell context-dependent, potentially contributing to the high failure rate of clinical trials.