The Role of Plasmacytoid and Myeloid Dendritic Cells in Induction of Asthma in a Mouse Model and the Effect of a TLR9 Agonist on Dendritic Cells

Biology of Lung Dendritic Cells at the Origin of Asthma

The role of dendritic cells in asthma

Plasmacytoid DCs and cancer: a new role for an enigmatic cell

Dendritic Cells in Fundamental and Clinical Immunology

ABSTRACTThe authors have recently demonstrated that alveolar macrophages (AMs) are important in protecting against early phase reactions and airway hyperresponsiveness following allergen challenge. To further understand the mechanisms involved, the authors investigated the capacity of AMs to modulate airway inflammation and cytokine levels in bronchoalveolar lavage (BAL). AMs from allergy-susceptible Brown Norway (BN) rats or allergy-resistant Sprague-Dawley (SD) rats were transferred into AM-depleted BN rats 24 hours prior to allergen challenge. Methacholine-induced airway hyperresponsiveness was examined 24 hours following ovalbumin challenge. Total cells, cell types, and cytokine levels (tumor necrosis factor [TNF], interleukin [IL]-4, IL-10, IL-12 and IL-13) in BAL were measured 24 hours after allergen challenge. The transfer of AMs from SD rats into AM-depleted BN rats 24 hours before allergen challenge eliminated methacholine-induced airway hyperresponsiveness, but did not modify the number and the type of inflammatory cells in BAL. Levels of IL-13 and TNF were significantly higher in BAL of BN rats compared with SD rats. Interestingly, IL-13 and TNF levels were significantly increased and inhibited, respectively, in BN rats that received AMs from SD rats compared with BN rats. Our data suggest that AM modulation of cytokine milieu is involved in the reduction of airway hyperresponsiveness.

The role of plasmacytoid dendritic cells (PDC), the major producers of alpha interferon upon viral infection, in the nasal mucosa is largely unknown. Here we examined the presence of PDC together with myeloid dendritic cells (MDC) in the nasal epithelia of healthy individuals, of asymptomatic patients with chronic nasal allergy, of patients undergoing steroid therapy, and of patients with infectious rhinitis or rhinosinusitis. Considerable numbers of PDC and MDC could be detected in the nasal epithelium. Furthermore, we demonstrate the expression of SDF-1, the major chemoattractant for PDC, in the nasal epithelium. PDC levels were significantly lower for patients with allergies than for healthy individuals. Interestingly, PDC and MDC were almost absent from patients who received treatment with glucocorticoids, while very high numbers of PDC were found for patients with recent upper respiratory tract infections. Our results demonstrate for the first time a quantitative analysis of PDC and MDC in the healthy nasal epithelium and in nasal epithelia from patients with different pathological conditions. With the identification of PDC, the major target cell for CpG DNA or immunostimulatory RNA, in the nasal epithelium, this study forms the basis for a local nasal application of such oligonucleotides for the treatment of viral infection and allergy.

Critical role of plasmacytoid dendritic cells in induction of oral tolerance

Topical Application of Cream-emulsified CD86 siRNA Ameliorates Allergic Skin Disease by Targeting Cutaneous Dendritic Cells

Reestablishing immune tolerance and long-term suppression of disease represent major therapeutic goals in rheumatoid arthritis (RA). Dendritic cells (DCs) likely play a central role in such regulation via the expansion and/or induction of Treg cells. The present study was undertaken to explore the contribution of DCs to the development of Treg cells in a human autoimmune disease setting. DC subsets were characterized by flow cytometry in the peripheral blood and synovial fluid of patients with RA. Proliferation of and cytokine release by naive CD4+CD25- T cells were measured in cocultures of these cells with DCs from patients with RA and healthy controls. The suppressive capacity of DC-polarized T cells was explored in vitro by a standard suppression assay. Only very low numbers of both plasmacytoid DCs (CD303+) and myeloid DCs (CD1c+) were present in the peripheral blood of patients with active RA. In contrast, patients with therapy-induced remission of RA exhibited higher numbers of circulating plasmacytoid DCs. Mature plasmacytoid DCs from RA patients with low disease activity, but not those from healthy controls, expressed high levels of indoleamine 2,3-dioxygenase and promoted the differentiation of allogeneic naive CD4+CD25- T cells into interleukin-10-secreting Treg cells, or Tr1 cells, that showed poor proliferation in vitro. Importantly, these plasmacytoid DC-primed Treg cells potently suppressed the proliferation of autologous naive CD4+ T cells, in a dose-dependent manner. These results demonstrate, for the first time, that human plasmacytoid DCs may be educated within the rheumatoid microenvironment to acquire a tolerogenic phenotype. Modulation of the immune response by plasmacytoid DCs might provide novel immune-based therapies in autoimmunity and transplantation.

Background/Objectives: This study aimed to characterize dendritic cell (DC) heterogeneity, immune associations, and prognostic relevance across three TP53-mutated tumor entities-high-grade serous ovarian cancer (HGSOC), triple-negative breast cancer, and endometrial cancer-focusing on plasmacytoid DCs (pDCs) in HGSOC. Methods: RNA-sequencing and clinical data of 603 patients from The Cancer Genome Atlas were analyzed. DC subset abundance was assessed for cDC progenitor, conventional DC type 1 (cDC1), conventional DC type 2 (cDC2), plasmacytoid DC (pDC), and mature DC by marker gene signatures. Differences in DC scores across tumors were analyzed using Kruskal-Wallis. Survival analyses were performed using Kaplan-Meier and Cox regression. Spearman's correlation was used to determine associations between parameters. Results: HGSOC showed the lowest pDC abundance, yet high pDC scores were independently associated with shorter PFS (HR = 1.55, 95% CI: 1.05-2.27; p = 0.027), representing the only DC-subset-related prognostic signal observed across tumor types. pDCs correlated positively with neutrophils and negatively with monocytes, and pDCs, cDC2s, and cDC progenitors correlated inversely with TMB. No consistent link was found between pDC and TP53 mutation classes. However, tumors harboring specific TP53 mutations within established hotspot regions exhibited significantly lower pDC levels (p = 0.015). Conclusions: Our findings reveal distinct DC infiltration patterns and highlight the immunological vulnerability of TP53-mutated HGSOC. pDCs appear to exert a tumor-promoting, immune-evasive role, suggesting that DC function depends on their programming and tumor context. Selective targeting of DC subsets may offer novel therapeutic opportunities in TP53-mutated, low-TMB cancers.

T 26th International Symposium of the Sapporo Cancer Seminar was held at Hokkaido University, Sapporo, Japan, on July 21–23, 2006. More than 120 researchers from various countries participated in the meeting (Fig. 1). The weather was fine every day, and the participants enjoyed walks around the university campus and dining at Chara Restaurant and Kirin Beer Garden. The symposium consisted of seminars presented by leading researchers from Japan and overseas in the field of innate immunity. Oral presentations were given by 12 researchers and poster presentations were given by 21 researchers. The symposium was organized by Dr Tsukasa Seya (Hokkaido University, Japan), as the chairman, and committee members Drs Misako Matsumoto, Hirofumi Sawa, Tokiyoshi Ayabe, and Roberto Cattaneo. Ms Saoko Kume was particularly involved in the organization of this meeting.

Plasmacytoid Dendritic Cells Are Proportionally Expanded at Diagnosis of Type 1 Diabetes and Enhance Islet Autoantigen Presentation to T-Cells Through Immune Complex Capture

The aim of this thesis was to characterize the role of plasmacytoid dendritic cells (pDCs) and lymphatic endothelial cells (LECs) in the modulation of peripheral T cell responses, with a particular focus on MHC class II-restricted antigen presentation. Depending on the immunological context, pDC MHCII-mediated antigen-presenting functions can be either tolerogenic or immunogenic. For instance, pDCs are maintained in a tolerogenic state by the tumor microenvironment. In the first part of this thesis, we asked the question whether tumor-associated pDCs could undergo a tolerogenic-to-immunogenic reprogramming following the intratumoral administration of CpG-B, a TLR9 ligand, along with a model MHC-II-restricted tumor antigenic peptide. LECs from lymph nodes (LN-LECs) were shown to impact peripheral CD8+ T cell responses, as antigen-presenting cells (APCs). Emerging evidence is in favor of a role for LN-LECs in CD4+ T cell tolerance to MHC-II-restricted antigens, although this phenomenon is still a matter of debate. In the second part of this thesis, we sought to determine the contribution of LN-LECs as MHC-II-restricted APCs to autoreactive CD4+ T cell responses in experimental autoimmune encephalomyelitis, a mouse model for multiple sclerosis.

Immobilized Chemokine Fields and Soluble Chemokine Gradients Cooperatively Shape Migration Patterns of Dendritic Cells

Cytokine levels in bronchoalveolar lavage fluid from patients with eosinophilic pneumonia (n=7), allergic alveolitis (n=11), (cryptogenic) fibrosing alveolitis (n=8), sarcoidosis (n=10) were determined, as well as levels in control samples from healthy non‐smoking volunteers (n=11). Fibronectin levels were increased in all the patient categories, the highest absolute levels of fibronectin (100‐fold increase) being found in eosinophilic pneumonia and allergic alveolitis. TGF‐β (transforming growth factor‐β) was significantly elevated in allergic alveolitis only. There was a significant difference between allergic alveolitis on the one hand and both sarcoidosis and fibrosing alveolitis on the other. Tumour necrosis factor‐α (TNF‐α) was significantly increased in eosinophilic pneumonia and allergic alveolitis; allergic alveolitis and fibrosing alveolitis differed significantly in this respect. Platelet‐derived growth factor‐BB (PDGF‐BB) levels were significantly elevated in allergic alveolitis and fibrosing alveolitis. It was found that the level of PDGF‐BB was significantly decreased in the case of sarcoidosis, with no overlapping with allergic alveolitis or fibrosing alveolitis. Interferon‐γ (IFN‐γ) was decreased in all patient categories. A significant difference in extent of the decrease was found between allergic alveolitis and sarcoidosis. The interstitial lung diseases thus differed in the pattern of cytokines expressed, indicating that these cytokines could well be a part of the pathogenic process, and also that the measurement of cytokine levels could be diagnostically useful.