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Priming of CD8+ T cells by peripheral dendritic cells exacerbates tau-mediated neurodegeneration.

Alzheimer's disease and primary tauopathies are marked by changes in adaptive immunity, with increased brain CD8+ T cells correlating with tau pathology severity. However, how peripheral T cells get primed to enter the brain and contribute to tau-mediated neurodegeneration remains unclear. In different disease conditions, conventional type 1 dendritic cells (cDC1s) cross-present antigens to prime CD8+ T cells into effector cells. We show that tauopathy mice lacking cDC1s or antigen cross-presentation are protected from neurodegeneration, with reduced brain CD8+ T cell infiltration and glial activation. The remaining CD8+ T cells exhibit limited clonal expansion, consistent with impaired priming. We further demonstrate that brain-derived antigens are presented in secondary lymphoid tissues, suggesting a site of T cell activation. Together, these findings establish cDC1-dependent peripheral priming as a key driver of CD8+ T cell accumulation in the brain and tau-mediated neurodegeneration.

Journal Article

Collagenase production by rheumatoid synovial cells: morphological and immunohistochemical studies of the dendritic cell.

The dendritic cells of dissociated, adherent rheumatoid synovial cell cultures are recognised by their distinctive morphological features--compact cytoplasm around the nucleus and long, branched cytoplasmic extensions. Such cells usually composed approximately 10% of the total adherent cell population but could vary from as few as 2% to as many as 40% with different synovial specimens. Histological studies have shown the cells to contain many mitochondria and large, spherical cytoplasmic inclusions which often distort the dendritic extensions. Although lysosomes were observed, no evidence for phagocytic activity was obtained. Immunolocalisation studies by means of a monospecific antibody to human collagenase have shown that the dendritic cell attached to a collagenous substratum produces and releases this enzyme in vitro. In contrast collagenase was detected in only a few of the fibroblast- and macrophage-like cells, and it was always intracellular. It is proposed that the dendritic cell may have an important role in the pathophysiology of the rheumatoid joint, particularly with regard to collagenase-mediated cartilage destruction.

Arthritis, Rheumatoid

Spatial habitat radiomics predicts tertiary lymphoid structure status and identifies an IDO1+ migratory dendritic cell axis in breast cancer.

BACKGROUND: Tertiary lymphoid structures (TLS) are spatially organized immune niches associated with therapeutic response and favorable outcomes in breast cancer (BC). However, TLS assessment currently relies on invasive tissue-based analyses, and the biological mechanisms underlying imaging-based TLS prediction remain poorly understood. METHODS: We developed and validated a spatial heterogeneity-based radiomic TLS signature (shTLS) using dynamic contrast-enhanced MRI to non-invasively predict TLS status across multicenter BC cohorts. Spatial habitat radiomics were used to capture intratumoral and peritumoral immune-related heterogeneity. Integrated multi-omics analyses, including transcriptomics, pathomics, genomics, single-cell RNA sequencing, immunohistochemistry, and multiplex immunofluorescence, were performed to biologically interpret shTLS-defined subgroups. Functional drug-sensitivity assays were conducted to assess therapeutic implications. RESULTS: The shTLS model achieved robust predictive performance across independent cohorts and molecular subtypes. High shTLS scores were associated with immune-inflamed tumors characterized by spatially clustered activated T cells and dendritic cells (DCs). In contrast, shTLS-low tumors exhibited an immunosuppressive spatial niche with peripheral accumulation of CD4+ PD-1+ T cells and plasma cells, increased immune-tumor separation, and enhanced inflammatory and immunoregulatory signaling. An indoleamine 2,3-dioxygenase 1 (IDO1)-associated immunoregulatory program was observed in the shTLS-low tumors, which appeared to be preferentially expressed by LAMP3+CCR7+ migratory DCs. Pharmacologic inhibition of IDO1 enhanced chemotherapy and CDK4/6 inhibitor sensitivity in vitro. CONCLUSION: This study establishes spatial radiomics as a non-invasive approach to decode TLS-associated immune ecosystems and supports the presence of an IDO1-associated immunosuppressive phenotype, providing biological insight and translational rationale for patient stratification and future combination strategies.

Humans

Myeloid Dendritic Cell Counts and Coronary Heart Disease: a Bidirectional Mendelian Randomization Study.

BACKGROUND: Coronary heart disease (CHD) remains a leading cause of morbidity and mortality worldwide, with immune and inflammatory mechanisms playing important roles in its pathogenesis. Dendritic cells (DCs) are key regulators of immune responses; however, the relationship between specific DC subsets and CHD risk remains incompletely understood. METHODS: This study conducted a bidirectional two-sample Mendelian randomization (MR) analysis using publicly available genome-wide association study (GWAS) summary statistics to investigate the potential associations between circulating dendritic cell traits and CHD. Genetic instruments for myeloid dendritic cells (Myeloid DCs) and plasmacytoid dendritic cells (Plasmacytoid DCs), including both absolute counts and relative proportions, were obtained from immune cell GWAS datasets. Summary statistics for CHD were derived from a large European-ancestry population. Multiple MR methods were applied, and sensitivity analyses were performed to assess the robustness of the findings and potential pleiotropic effects. RESULTS: Nominal associations between genetically predicted Myeloid DC counts and CHD risk were observed in the MR-Egger and weighted median analyses, whereas the inverse variance weighted analysis demonstrated no significant association. These nominal associations did not remain statistically significant after correction for multiple testing. No significant associations were observed for Plasmacytoid DC counts or for the relative proportions of either DC subset. Reverse MR analyses were inconclusive due to wide confidence intervals, precluding meaningful inference regarding a causal effect of CHD on DC-related traits. Sensitivity analyses revealed no substantial heterogeneity or horizontal pleiotropy. CONCLUSIONS: This bidirectional MR study explored the potential relationships between circulating dendritic cell traits and CHD risk. Although nominal associations involving Myeloid DC counts were observed in secondary MR analyses, no robust evidence supporting an association remained after correction for multiple testing. Further studies using larger datasets and functional approaches are warranted to clarify the role of dendritic cells in CHD.

Humans

Genomic and Transcriptomic Landscape of Epstein-Barr Virus-Positive Inflammatory Follicular Dendritic Cell Sarcoma: A Multicenter Study.

Epstein-Barr virus (EBV)-positive inflammatory follicular dendritic cell sarcoma (EBV+ IFDCS) is a rare indolent malignant neoplasm, which occurs almost exclusively in the liver or spleen and may arise from a common EBV-infected mesenchymal cell that differentiates along the follicular or fibroblastic dendritic cell pathway. Despite its rarity, it presents a pressing need for an improved understanding of its genetic underpinnings and potential treatment strategies for recurrent or disseminated cases. To address this, we conducted comprehensive whole-exome sequencing and transcriptome sequencing (mRNA-seq) analyses on 31 and 6 cases of EBV+ IFDCS, respectively, collected from multiple centers in China. We also compared the genetic features of EBV+ IFDCS with those of other EBV-associated malignancies. Our analyses revealed a relatively high somatic mutation rate and widespread copy number variations affecting the major histocompatibility complex-I/II in EBV+ IFDCS. Integrated mutational profiling identified key signaling pathways involved in epigenetic regulation, NF-κB signaling, RTK/RAS/PI(3)K, and the Hippo pathway. Furthermore, we identified several frequently altered genes that could serve as potential therapeutic targets in EBV+ IFDCS. Transcriptomic analysis unveiled significant upregulation of pathways related to virus infection, immune responses, and multiple immune checkpoint genes in EBV+ IFDCS. Comparative analysis demonstrated clear genetic distinctions between EBV+ IFDCS and other EBV-associated tumors. In conclusion, our study provides comprehensive insights into the unique genomic and transcriptomic landscape of EBV+ IFDCS. We have identified multiple genetic alterations that likely contribute to the development and progression of this malignancy. Our results suggest that targeted therapy and immune checkpoint inhibitors may hold promise as potential therapeutic approaches for patients with recurrent or disseminated EBV+ IFDCS.

Humans

Embryology of the epidermis: ultrastructural aspects. III. Maturation and primary appearance of dendritic cells in the mouse with mammalian comparisons.

The epidermis of mice ranging in age from prenatal day 17 through postnatal day 4 and, in addition, postnatal day 18, was studied with the electron microscope. In the 17 day fetus, the periderm may or may not be present and a stratum corneum is developing in the latter case. The cells of the strata spinosum and granulosum contain much glycogen and many keratinosomes and homogeneous keratohyalin granules which appear to line up in a row near the distal cell membranes, fuse and form keratinized cells which contain material similar in density to that of the individual keratohyalin granules. In the 18 to 20 day fetuses, no periderm is present. The stratum corneum becomes well-developed. The quantity of glycogen decreases but the number of keratinosomes and keratohyalin granules increases. Some cells in the basal region contain necrotic phagocytosed cells. Few changes occur in the epidermis of the neonate, although the stratum corneum increases in thickness. In the early postnatal period, the mouse epidermis is mature in appearance and resembles that of man. By postnatal day 18, the whole epidermis is much thinner, although all classical strata can usually be identified. The primary appearance and subsequent maturation of epidermal dendritic cells was also studied in the mouse during the embryonic, fetal, early postnatal and 18 day postnatal periods. Melanocytes which lacked cell processes were first identified in the 15 day fetus. Melanocyte cell processes and an increasing number of melanosomes, as well as melanocytes, are present between prenatal day 18 and postnatal day 3. On postnatal day 4, fewer melanocytes are present and they contain vacuoles. Phagocytosed melanocytes are also present within basal keratinocytes. Undifferentiated dendritic cells or indeterminate cells are observed beginning on prenatal day 16. These cells do not appear to increase significantly in number subsequently. On postnatal day 18, Langerhans cells and indeterminate cells are present but no melanocytes can be identified. No Merkel cells were observed. Mitotic dendritic cells or dendritic cells traversing the basal lamina were not observed.

Age Factors

Dendritic cells in the rat spleen follicles. A combined immuno- and enzyme histochemical study.

Follicles of peripheral lymphoid organs (rat) contain a type of non-lymphoid cell which is capable of arresting antigen-antibody complexes at the cell surface. These so-called dendritic cells can be visualized in immunized rats by staining antigen-antibody complexes with immunohistoperoxidase techniques. The present study concerns a classification of these cells and comparison with known non-lymphoid cell types such as macrophages, marginal metallophils and tingible body macrophages in the rat spleen follicles. Immunoenzyme histochemical and (enzyme) histochemical techniques have been combined in the same tissue sections to correlate the functional capacity of binding immune complexes with morphological characteristics or phagocytic capacity. Dendritic cells show silver affinity but do not demonstrate a characteristic pattern of hydrolytic enzymes or phagocytosis.

Acid Phosphatase

Expression of MHC antigens by mouse thymic dendritic cells.

Thymic epithelial cells express MHC antigens in several different patterns. I-A is present throughout the thymic cortex on dendritic cells. The remainder of the I region and H-2K/D are expressed on dendritic cells apparently only variably in the cortex (at least in some haplotypes). All MHC antigens tested are present in the medulla on epithelial cells; expression on medullary lymphocytes cannot be evaluated. Monoclonal anti-MHC antibodies confirm these results. The significance of these findings to T cell maturation is discussed.

Animals

Discrimination and dendritic cell abundance among older adults in the health and retirement study.

We investigated whether peripheral blood dendritic cell (DC) abundance varies as a function of discrimination exposure in a national sample of older US adults (aged 50 + years) from the 2016 Venous Blood Study, a US Health and Retirement Study biomarker project. Density of myeloid DCs (mDC) and plasmacytoid DCs (pDC) were measured using multiparameter flow cytometry. Discrimination was assessed using the validated Everyday Discrimination Scale. Weighted linear regression models quantified associations between discrimination and natural-log transformed DC abundance, controlling for sociodemographic factors, chronic health conditions, and health behaviors. We tested whether these associations varied by race/ethnicity. For mDC, we found no significant overall association with discrimination. However, race/ethnicity significantly modified this relationship: among non-Hispanic White participants, a 1-SD increase in discrimination was associated with a non-significant 1.4 % increase in mDC count (p = 0.20), while non-Hispanic Black participants showed a significant 4.6 % decrease (interaction p = 0.021). For pDC, a 1-SD change in discrimination was significantly associated with a 2.4 % increase in abundance across all participants (95 % CI: 0.6 %, 4.3 %, p = 0.010), with no significant effect modification by race/ethnicity. In this nationally representative study of older Americans, discrimination exposure was associated with altered dendritic cell abundance, with distinct patterns by cell type and race/ethnicity. Increased pDC counts across all racial/ethnic groups suggest a common immunological response to discrimination, while divergent mDC responses between non-Hispanic Black and White participants indicate race-specific immune modulation. These findings reveal complex cellular pathways through which discrimination may differentially influence immune function and contribute to health inequities.

Aged

Dendritic cells control tertiary lymphoid structure development and maintenance in cancer.

Tertiary lymphoid structures (TLSs) are associated with immunotherapy response, yet the mechanisms controlling their formation and maintenance remain unclear. Using spatial transcriptomics and multiplex imaging across human tumors, we found that CCR7+ mature dendritic cells (DCs) accumulate in TLSs. In a mouse non-small cell lung cancer model that forms mature TLSs, we show that early TLS development requires interferon-γ (IFN-γ)-driven type 1 conventional dendritic cell (cDC1) maturation, migration to tumor-draining lymph nodes (tdLNs), and T cell recruitment. As tumors progress, TLSs persist independently of tdLN T cell egress, coinciding with cDC1 accumulation within intratumoral CCL19 stromal hubs. There, cDC1-major histocompatibility complex class 1 (MHC-I) and -MHC-II concomitant antigen presentation, along with CD40 signaling, sustain TLS, T follicular helper (TFH) cell pool, germinal centers, and tumor-specific immunoglobulin G (IgG). These findings highlight local mature cDC1s as key TLS orchestrators and potential targets to enhance antitumor TLS function.

Animals

Decreased TXNRD1 is associated with resistance to tagraxofusp in blastic plasmacytoid dendritic cell neoplasms, as seen in phase II.

Tagraxofusp is a CD123-targeted therapy comprised of a recombinant human interleukin-3 (IL-3) fused to a truncated diphtheria toxin payload. It is the first approved treatment specifically for patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN). To identify biomarkers of response, bone marrow samples from 12 BPDCN patients who were treated with tagraxofusp in the pivotal phase II trial (NCT02113982) were profiled longitudinally using a gene panel and single-cell RNA sequencing. Residual tumor cells following tagraxofusp expressed lower levels of TXNRD1 that would reduce the efficacy of tagraxofusp. In support of this, enzymatic inhibition of TXNRD1 resulted in higher viability of CAL-1 BPDCN cells following tagraxofusp. Responders had either wild-type or missense TET2 mutations, while transient and non-responders had at least one truncating TET2 mutation. Examples of these mutations within the catalytic domain of TET2 were constructed and transduced into cells. Missense and truncating mutants displayed reduced sensitivities to hypomethylating agents and prolonged S-phase stasis. These results suggest that the levels of TXNRD1 interact with intrinsic TET2 truncating mutations within the bone marrow to modulate patient response to tagraxofusp.

Female

Lymphoid dendritic cells are potent stimulators of the primary mixed leukocyte reaction in mice.

Dendrite cells (DCs) are a new cell type initially identified in mouse lymphoid organs. Recently, DCs have been purified from mouse spleen. This paper demonstrates a functional role of DCs: they are potent stimulators of the primary mixed leukocytes reaction (MLR). As few as 300-1000 DCs doubled the proliferative activity of 5 X 10(6) allogeneic responder spleen cells, while 0.3-1.0 X 10(5) DCs induced a maximal stimulation of 30- to 80-fold. Between these extremes, the log of the MLR response increased linearly with the log of DC numbers. This dose-response assay was then used to compare the potency of purified DCs with that of other heterogeneous lymphoid populations, many of which gave dose-response curves with similar slopes. The potency of purified DCs as MLR stimulators was 100-300 times greater than that of unfractionated spleen cells. When spleen cells were fractionated by simple physical techniques, MLR-stimulating capacity in the subpopulations correlated closely with DC numbers. Removal of splenic B or T lymphocytes, by anti-immunoglobulin or anti-brain serum plus complement, did not reduce MLR-stimulating capacity. Finally, several populations, enriched in mononuclear phagocytes but lacking in DCs, stimulated weakly if at all. We conclude that DCs are a potent stimulating cell and are at least 100 times more effective than other major cell subclasses--i.e., B and T lymphocytes and macrophages.

Animals

EP300-mediated lactylation leads to ulcerative colitis via CD86-positive plasmacytoid dendritic cells: A Mendelian randomization and mediation analysis.

This study explores the potential mechanism between lactylation and ulcerative colitis (UC) using two-sample Mendelian randomization and multi-omics analysis. This study employed expression quantitative trait loci and protein quantitative trait loci as exposures, with UC from the Finnish database as the outcome, to conduct Mendelian randomization analysis on lactylation-related target genes, aiming to investigate the causal relationships between these exposures and the outcome. Sensitivity and pleiotropy tests, combined with colocalization analysis, are performed to identify the best target genes and ensure the robustness of the results. Finally, immune cells are included for mediation analysis between lactylation and UC to explore potential mechanisms of action. Through Mendelian randomization analysis combined with sensitivity and pleiotropy tests, 2 lactylation target genes were found to have a significant causal relationship with UC. Subsequent colocalization analysis confirmed EP300 as a potential gene target. After including immune cells in the mediation analysis, it was discovered that there is a potential mechanism involving EP300, CD86+ plasmacytoid dendritic cells (pDCs), and UC. There is a significant causal relationship between lactylation and UC. Furthermore, the lactylation-modified gene EP300 may lead to UC occurrence by regulating CD86+ pDCs.

Humans

Ramification patterns of ganglion cell dendrites in the retina of the albino rat.

Ganglion cell morphology has been analyzed in the retina of the adult, albino rat by the Golgi technique and evidence has been obtained that the ganglion cells of this species show a far greater variety and complexity of organization than described previously. Both diffuse ganglion cells, whose dendrites ramify throughout the inner plexiform layer, and stratified ganglion cells, whose dendritic branching is restricted to one or two planes, have been identified. Evidence is also presented for distinct stratification of the inner plexiform layer in this species, based on radioautographic analysis following intravitreal injection of tritiated amino acids.

Animals

Intestinal plasmacytoid dendritic cells preferentially produce interferon lambda, contributing to localized innate immune responses.

The healthy intestine maintains homeostasis in part via immune responses to microbiota, which includes basal production of interferon cytokines. Previous work showed that Type III Interferon (IFN-λ) stimulates localized pockets of interferon-stimulated genes (ISGs) in the adult mouse intestinal epithelium at homeostasis that provide preemptive protection from viral pathogens. Here, we demonstrate that a major source of homeostatic IFN-λ production in the intestine is a population of epithelium-associated plasmacytoid dendritic cells (pDC). Expansion of the pDC population increases epithelial ISG expression at homeostasis, suggesting the abundance of these cells is a limiting factor in IFN-λ responses. On the other hand, depletion of pDC or bone marrow reconstitution with IFN-λ-deficient pDC results in reduced expression of homeostatic ISGs in the intestinal epithelium. Notably, intestinal pDC preferentially produce homeostatic IFN-λ, whereas splenic pDC produce Type I IFNs. Comparison of intestinal and splenic pDC reveal tissue-specific changes in gene expression and genomic accessibility, including evidence of responses to transforming growth factor beta (TGF-β) in the intestine. Isolated gut pDC produce more IFN-λ than splenic pDC upon stimulation, and pretreatment of a human pDC cell line with TGF-β results in enhanced transcription of IFN-λ upon stimulation. This study demonstrates that pDC are a substantial source of homeostatic IFN-λ in the intestine and implicates the barrier cytokine TGF-β in regulating IFN types produced by pDC upon stimulation. Reprogramming of recruited pDC by tissue cytokines may have important implications for balancing effective antimicrobial responses with damaging inflammation at barrier tissues.

Animals

Exercise during development induces an increase in Purkinje cell dendritic tree size.

Mice allowed to exercise during the late postnatal period had Purkinje cells with larger dendritic trees and greater numbers of spines than littermates whose physical activity was severly restricted. These changes in Purkinje cells were accompanied by a selective reduction in the thickness of the cerebellar molecular layer. The data provide evidence for cerebellar plasticity during late development and demonstrate that physical activity can modify the development of Purkinje cell dendrites.

Animals

The nature of dendritic cells of the epidermis of the white guinea pig.

The melanocytes, the intermediate cells of Billingham and Medawar and the Langerhans' cells of the epidermis of the white guinea pig were found to be positive to Bielschowsky's silver and Gomori's acetylcholinesterase reactions. The melanocytes were full of Nissl substance. On these evidences, supported by other morphological and histochemical characteristics, the dendritic cells of the epidermis were considered to be nervous structures.

Animals

Plasmacytoid dendritic cells in the intestine preferentially produce interferon lambda at homeostasis contributing to tonic localized innate immune responses.

The healthy intestine maintains homeostasis in part via immune responses to microbiota, which includes basal production of interferon cytokines. Previous work showed that Type III Interferon (IFN-λ) stimulates localized pockets of interferon-stimulated genes (ISGs) in the adult mouse intestinal epithelium at homeostasis that provide preemptive protection from viral pathogens. Here, we demonstrate that a major source of homeostatic IFN-λ production in the intestine is a population of epithelium-associated plasmacytoid dendritic cells (pDC). Depletion of bacterial microbiota in the intestine also reduces pDC abundance, and pDC depletion or bone marrow reconstitution with IFN-λ-deficient pDC results in reduced expression of homeostatic ISGs in the intestinal epithelium. Notably, intestinal pDC preferentially produce IFN-λ over Type I IFNs whereas splenic pDC produce more Type I IFNs. Comparison of intestinal and splenic pDC reveal tissue-specific changes in gene expression and genomic accessibility, including evidence of responses to transforming growth factor beta (TGF-β) in the intestine. Isolated gut pDC produce more IFN-λ than splenic pDC upon stimulation, and pre-treatment of a human pDC cell line with TGF-β results in enhanced production of IFN-λ upon stimulation. This study demonstrates that pDC are an important source of homeostatic IFN-λ in the intestine and defines the role of barrier cytokine TGF-β in regulating IFN types produced by pDC upon stimulation. Reprogramming of recruited pDC by tissue cytokines may have important implications for balancing effective antimicrobial responses with damaging inflammation at barrier tissues.

Journal Article