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Chauhan P, Dandapat J, Sarkar A, Saha B. March of Mycobacterium: miRNAs intercept host cell CD40 signalling. Clin Transl Immunology 2020; 9:e1179. [PMID: 33072321 PMCID: PMC7541823 DOI: 10.1002/cti2.1179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/22/2020] [Accepted: 08/22/2020] [Indexed: 12/12/2022] Open
Abstract
The disease tuberculosis is fatal if untreated. It is caused by the acid‐fast bacilli Mycobacterium tuberculosis. Mycobacterium resides and replicates within the alveolar macrophages, causing inflammation and granuloma, wherein macrophage‐T cell interactions enhance the inflammation‐causing pulmonary caseous lesions. The first interactions between Mycobacterium and the receptors on macrophages decide the fate of Mycobacterium because of phagolysosomal impairments and the expression of several miRNAs, which may regulate CD40 expression on macrophages. While the altered phagolysosomal functions impede antigen presentation to the T cell‐expressed antigen receptor, the interactions between the macrophage‐expressed CD40 and the T cell‐expressed CD40‐ligand (CD40L or CD154) provide signals to T cells and Mycobacterium‐infected macrophages. These two functions significantly influence the resolution or persistence of Mycobacterium infection. CD40 controls T‐cell polarisation and host‐protective immunity by eliciting interleukin‐12p40, nitric oxide, reactive oxygen species and IFN‐γ production. Indeed, CD40‐deficient mice succumb to low‐dose aerosol infection with Mycobacterium because of deficient interleukin (IL)‐12 production leading to impaired IFN‐γ‐secreting T‐cell response. In contrast, despite generating fewer granulomas, the CD40L‐deficient mice developed anti‐mycobacterial T‐cell responses to the levels observed in the wild‐type mice. These host‐protective responses are significantly subdued by the Mycobacterium‐infected macrophage produced TGF‐β and IL‐10, which promote pro‐mycobacterial T‐cell responses. The CD40‐CD40L‐induced counteractive immune responses against Mycobacterium thus present a conundrum that we explain here with a reconciliatory hypothesis. Experimental validation of the hypothesis will provide a rationale for designing anti‐tubercular immunotherapy.
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Affiliation(s)
| | | | - Arup Sarkar
- Trident Academy of Creative Technology Bhubaneswar India
| | - Bhaskar Saha
- National Centre for Cell Science (NCCS) Pune India.,Trident Academy of Creative Technology Bhubaneswar India
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2
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The exhausted CD4+CXCR5+ T cells involve the pathogenesis of human tuberculosis disease. Int J Infect Dis 2018; 74:1-9. [DOI: 10.1016/j.ijid.2018.06.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/31/2018] [Accepted: 06/14/2018] [Indexed: 12/18/2022] Open
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3
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Versteven M, Van den Bergh JMJ, Marcq E, Smits ELJ, Van Tendeloo VFI, Hobo W, Lion E. Dendritic Cells and Programmed Death-1 Blockade: A Joint Venture to Combat Cancer. Front Immunol 2018; 9:394. [PMID: 29599770 PMCID: PMC5863527 DOI: 10.3389/fimmu.2018.00394] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 02/13/2018] [Indexed: 12/31/2022] Open
Abstract
Two decades of clinical cancer research with dendritic cell (DC)-based vaccination have proved that this type of personalized medicine is safe and has the capacity to improve survival, but monotherapy is unlikely to cure the cancer. Designed to empower the patient’s antitumor immunity, huge research efforts are set to improve the efficacy of next-generation DC vaccines and to find synergistic combinations with existing cancer therapies. Immune checkpoint approaches, aiming to breach immune suppression and evasion to reinforce antitumor immunity, have been a revelation in the immunotherapy field. Early success of therapeutic antibodies blocking the programmed death-1 (PD-1) pathway has sparked the development of novel inhibitors and combination therapies. Hence, merging immunoregulatory tumor-specific DC strategies with PD-1-targeted approaches is a promising path to explore. In this review, we focus on the role of PD-1-signaling in DC-mediated antitumor immunity. In the quest of exploiting the full potential of DC therapy, different strategies to leverage DC immunopotency by impeding PD-1-mediated immune regulation are discussed, including the most advanced research on targeted therapeutic antibodies, lessons learned from chemotherapy-induced immune activation, and more recent developments with soluble molecules and gene-silencing techniques. An overview of DC/PD-1 immunotherapy combinations that are currently under preclinical and clinical investigation substantiates the clinical potential of such combination strategies.
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Affiliation(s)
- Maarten Versteven
- Laboratory of Experimental Hematology, Faculty of Medicine and Health Sciences, Vaccine and Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Antwerp, Belgium
| | - Johan M J Van den Bergh
- Laboratory of Experimental Hematology, Faculty of Medicine and Health Sciences, Vaccine and Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Antwerp, Belgium
| | - Elly Marcq
- Center for Oncological Research Antwerp, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
| | - Evelien L J Smits
- Laboratory of Experimental Hematology, Faculty of Medicine and Health Sciences, Vaccine and Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Antwerp, Belgium.,Center for Oncological Research Antwerp, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.,Center for Cell Therapy and Regenerative Medicine, Antwerp University Hospital, Antwerp, Belgium
| | - Viggo F I Van Tendeloo
- Laboratory of Experimental Hematology, Faculty of Medicine and Health Sciences, Vaccine and Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Antwerp, Belgium
| | - Willemijn Hobo
- Laboratory of Hematology, Department of Laboratory Medicine, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Eva Lion
- Laboratory of Experimental Hematology, Faculty of Medicine and Health Sciences, Vaccine and Infectious Disease Institute (VAXINFECTIO), University of Antwerp, Antwerp, Belgium.,Center for Cell Therapy and Regenerative Medicine, Antwerp University Hospital, Antwerp, Belgium
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Parlato S, Chiacchio T, Salerno D, Petrone L, Castiello L, Romagnoli G, Canini I, Goletti D, Gabriele L. Impaired IFN-α-mediated signal in dendritic cells differentiates active from latent tuberculosis. PLoS One 2018; 13:e0189477. [PMID: 29320502 PMCID: PMC5761858 DOI: 10.1371/journal.pone.0189477] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 11/27/2017] [Indexed: 12/12/2022] Open
Abstract
Individuals exposed to Mycobacterium tuberculosis (Mtb) may be infected and remain for the entire life in this condition defined as latent tuberculosis infection (LTBI) or develop active tuberculosis (TB). Among the multiple factors governing the outcome of the infection, dendritic cells (DCs) play a major role in dictating antibacterial immunity. However, current knowledge on the role of the diverse components of human DCs in shaping specific T-cell response during Mtb infection is limited. In this study, we performed a comparative evaluation of peripheral blood circulating DC subsets as well as of monocyte-derived Interferon-α DCs (IFN-DCs) from patients with active TB, subjects with LTBI and healthy donors (HD). The proportion of circulating myeloid BDCA3+ DCs (mDC2) and plasmacytoid CD123+ DCs (pDCs) declined significantly in active TB patients compared to HD, whereas the same subsets displayed a remarkable activation in LTBI subjects. Simultaneously, the differentiation of IFN-DCs from active TB patients resulted profoundly impaired compared to those from LTBI and HD individuals. Importantly, the altered developmental trait of IFN-DCs from active TB patients was associated with down-modulation of IFN-linked genes, marked changes in molecular signaling conveying antigen (Ag) presentation and full inability to induce Ag-specific T cell response. Thus, these data reveal an important role of IFN-α in determining the induction of Mtb-specific immunity.
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Affiliation(s)
- Stefania Parlato
- Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Teresa Chiacchio
- Translational Research Unit, Department of Epidemiology and Preclinical Research, "L. Spallanzani" National Institute for Infectious Diseases (INMI) IRCCS, Rome, Italy
| | - Debora Salerno
- Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Rome, Italy
| | - Linda Petrone
- Translational Research Unit, Department of Epidemiology and Preclinical Research, "L. Spallanzani" National Institute for Infectious Diseases (INMI) IRCCS, Rome, Italy
| | | | - Giulia Romagnoli
- Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Irene Canini
- Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Delia Goletti
- Translational Research Unit, Department of Epidemiology and Preclinical Research, "L. Spallanzani" National Institute for Infectious Diseases (INMI) IRCCS, Rome, Italy
- * E-mail: (LG); (DG)
| | - Lucia Gabriele
- Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
- * E-mail: (LG); (DG)
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Brown RE, Hunter RL, Hwang SA. Morphoproteomic-Guided Host-Directed Therapy for Tuberculosis. Front Immunol 2017; 8:78. [PMID: 28210262 PMCID: PMC5288338 DOI: 10.3389/fimmu.2017.00078] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 01/17/2017] [Indexed: 01/08/2023] Open
Abstract
In an effort to develop more effective therapy for tuberculosis (TB), research efforts are looking toward host-directed therapy, reprograming the body's natural defenses to better control the infection. While significant progress is being made, the efforts are limited by lack of understanding of the pathology and pathogenesis of adult type TB disease. We have recently published evidence that the developing lesions in human lungs are focal endogenous lipid pneumonia that constitutes a region of local susceptibility in a person with strong systemic immunity. Since most such lesions regress spontaneously, the ability to study them directly with immunohistochemistry provides means to investigate why some progress to clinical disease while others asymptomatically regress. Furthermore, this should enable us to develop more effective host-directed therapies. Morphoproteomics has proven to be an effective means of characterizing protein expression that can be used to identify metabolic pathways, which can lead to more effective therapies. The purpose of this perspective will argue that using morphoproteomics on human TB lung tissue is a particularly promising method to direct selection of host-directed therapeutics.
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Affiliation(s)
- Robert E Brown
- Department of Pathology and Laboratory Medicine, McGovern Medical School, University of Texas Health Science Center at Houston , Houston, TX , USA
| | - Robert L Hunter
- Department of Pathology and Laboratory Medicine, McGovern Medical School, University of Texas Health Science Center at Houston , Houston, TX , USA
| | - Shen-An Hwang
- Department of Pathology and Laboratory Medicine, McGovern Medical School, University of Texas Health Science Center at Houston , Houston, TX , USA
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Sakhno LV, Shevela EY, Tikhonova MA, Ostanin AA, Chernykh ER. The Phenotypic and Functional Features of Human M2 Macrophages Generated Under Low Serum Conditions. Scand J Immunol 2016; 83:151-9. [PMID: 26678544 DOI: 10.1111/sji.12401] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 11/27/2015] [Indexed: 01/13/2023]
Abstract
The phenotypic and functional features of human M2 macrophages, in particular, their immunosuppressive activity, can considerably vary depending on M2 polarizing stimulus. This study was aimed at the investigation of cytokine production and pro-apoptogenic/inhibitory molecule expression in macrophages generated with GM-CSF using either standard conditions (M1) or deficiency of serum/growth factors (M2-LS cells). In contrast to M1, M2-LS cells were characterized by an enhanced content of CD206(+), B7-H1(+), FasL(+) and TRAIL(+) cells along with a decreased production of IFN-γ, IL-5, IL-6, IL-13, TNF-α, IL-17 and MCP-1. In addition, M2-LS exhibited a lower T cell stimulatory activity in MLC that was associated with the higher numbers of apoptotic and the lower numbers of proliferating T cells. B7-H1 plays a key role in M2-LS-mediated cytotoxic effects as the neutralization of B7-H1 reduces the apoptosis-inducing activity of M2-LS, while the blocking of CD206 and TRAIL reduces the cytostatic activity of M2 macrophages.
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Affiliation(s)
- L V Sakhno
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - E Ya Shevela
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - M A Tikhonova
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - A A Ostanin
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - E R Chernykh
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
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Chernykh ER, Leplina OY, Tikhonova MA, Seledtsova NV, Tyrinova TV, Khonina NA, Ostanin AA, Pasman NM. Elevated levels of dehydroepiandrosterone as a potential mechanism of dendritic cell impairment during pregnancy. BMC Immunol 2015; 16:2. [PMID: 25636695 PMCID: PMC4322645 DOI: 10.1186/s12865-014-0065-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 12/11/2014] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND This study aimed to test the hypothesis that immune dysfunction and the increased risk of spontaneous abortion in pregnant women with hyperandrogenia (HA) are caused by the reduced tolerogenic potential of dendritic cells (DCs) that results from elevated levels of dehydroepiandrosterone sulfate (DHEAS). METHODS The phenotypic and functional properties of monocyte-derived DCs generated from blood monocytes from non-pregnant women, women with a normal pregnancy, or pregnant women with HA, as well as the in vitro effects of DHEAS on DCs in healthy pregnant women were investigated. RESULTS In a normal pregnancy, DCs were shown to be immature and are characterized by a reduced number of CD83(+) and CD25(+) DCs, the ability to stimulate type 2 T cell responses and to induce T cell apoptosis. By contrast, DCs from pregnant women with HA had a mature phenotype, were able to stimulate both type 1 (IFN-γ) and type 2 (IL-4) T cell responses, and were characterized by lower B7-H1 expression and cytotoxic activity against CD8(+) T cells. The addition of DHEAS to cultures of DCs from healthy pregnant women induced the maturation of DCs and increased their ability to activate type 1 T cell responses. CONCLUSION Our data demonstrated the reduction in the tolerogenic potential of DCs from pregnant women with HA, and revealed new mechanisms involved in the hormonal regulation of DCs mediated by DHEAS.
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Affiliation(s)
- Elena R Chernykh
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Olga Yu Leplina
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Marina A Tikhonova
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Nataliya V Seledtsova
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Tamara V Tyrinova
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Nataliya A Khonina
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Alexandr A Ostanin
- Laboratory of Cellular Immunotherapy, Research Institute of Fundamental and Clinical Immunology, 14, Yadrintsevskaya St., 630099, Novosibirsk, Russia.
| | - Nataliya M Pasman
- Novosibirsk State University, 2, Pirogova St., 630090, Novosibirsk, Russia.
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Leplina OY, Tyrinova TV, Tikhonova MA, Ostanin AA, Chernykh ER. Interferon alpha induces generation of semi-mature dendritic cells with high pro-inflammatory and cytotoxic potential. Cytokine 2014; 71:1-7. [PMID: 25174880 DOI: 10.1016/j.cyto.2014.07.258] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 07/31/2014] [Indexed: 01/04/2023]
Abstract
Dendritic cell-based vaccines are considered as a new and promising immunotherapeutic approach for cancer treatment. However, the choice of optimal protocol of dendritic cell generation in vitro represents the major challenge. Here, we compared phenotype and functional characteristics of human monocyte-derived dendritic cells (DCs) generated in the presence of IL-4/GM-CSF (IL4-DCs) and IFNα/GM-CSF (IFN-DCs). We showed that IFN-DCs displayed semi-mature phenotype and expressed higher level of CD123, TNF-related apoptosis-inducing ligand (TRAIL) and B7-H1 molecules in comparison with IL4-DCs. LPS-stimulated IFN-DCs were characterized by greater production of Th1/pro-inflammatory (IFN-γ, IL-2, IL-1β, TNF-α, IL-17), Тh2/anti-inflammatory cytokines (IL-10, IL-5), hematopoietic growth factors (G-CSF) and chemokines (MCP-1). These data indicated more pronounced ability of IFN-DCs to induce cellular immune response as well as humoral immune response compared to IL4-DCs. LPS-stimulated IFN-DCs possessed higher direct cytotoxic activity against TRAIL-sensitive tumor cell line Jurkat and similar cytotoxicity against TRAIL-resistant tumor HEp-2 cells. Besides, IFN-DCs and IL4-DCs equally induced apoptosis of activated CD4(+) and CD8(+) T cells. These results suggest that IFN-DCs can be used as potent cell-based curative therapies for individuals with cancer.
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Affiliation(s)
- Olga Yu Leplina
- Institute of Clinical Immunology SB RAMS, 14 Yadrintsevskaya Str., 630099 Novosibirsk, Russia(1)
| | - Tamara V Tyrinova
- Institute of Clinical Immunology SB RAMS, 14 Yadrintsevskaya Str., 630099 Novosibirsk, Russia(1).
| | - Marina A Tikhonova
- Institute of Clinical Immunology SB RAMS, 14 Yadrintsevskaya Str., 630099 Novosibirsk, Russia(1)
| | - Alexander A Ostanin
- Institute of Clinical Immunology SB RAMS, 14 Yadrintsevskaya Str., 630099 Novosibirsk, Russia(1)
| | - Elena R Chernykh
- Institute of Clinical Immunology SB RAMS, 14 Yadrintsevskaya Str., 630099 Novosibirsk, Russia(1)
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Tel J, Anguille S, Waterborg CEJ, Smits EL, Figdor CG, de Vries IJM. Tumoricidal activity of human dendritic cells. Trends Immunol 2013; 35:38-46. [PMID: 24262387 PMCID: PMC7106406 DOI: 10.1016/j.it.2013.10.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 10/18/2013] [Accepted: 10/21/2013] [Indexed: 12/11/2022]
Abstract
Human DC subsets can exert tumoricidal activity. Killer DCs exploit several mechanisms for direct killing of target cells, including TRAIL and granzyme B. Antigen presentation and/or IFN production are important additional effector functions. Killer DCs are promising targets for immunotherapeutic strategies.
Dendritic cells (DCs) are a family of professional antigen-presenting cells (APCs) that are able to initiate innate and adaptive immune responses against pathogens and tumor cells. The DC family is heterogeneous and is classically divided into two main subsets, each with its unique phenotypic and functional characteristics: myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). Recent results have provided intriguing evidence that both DC subsets can also function as direct cytotoxic effector cells; in particular, against cancer cells. In this review, we delve into this understudied function of human DCs and discuss why these so-called killer DCs might become important tools in future cancer immunotherapies.
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Affiliation(s)
- Jurjen Tel
- Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Sébastien Anguille
- Laboratory of Experimental Hematology, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
| | - Claire E J Waterborg
- Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Evelien L Smits
- Laboratory of Experimental Hematology, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium; Center for Oncological Research, University of Antwerp, Antwerp, Belgium
| | - Carl G Figdor
- Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - I Jolanda M de Vries
- Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; Department of Medical Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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Nikolic T, Roep BO. Regulatory multitasking of tolerogenic dendritic cells - lessons taken from vitamin d3-treated tolerogenic dendritic cells. Front Immunol 2013; 4:113. [PMID: 23717310 PMCID: PMC3653108 DOI: 10.3389/fimmu.2013.00113] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/29/2013] [Indexed: 01/08/2023] Open
Abstract
Tolerogenic dendritic cells (DCs) work through silencing of differentiated antigen-specific T cells, activation and expansion of naturally occurring T regulatory cells (Tregs), transfer of regulatory properties to T cells, and the differentiation of naïve T cells into Tregs. Due to an operational definition based on T cell activation assays, the identity of tolerogenic DCs has been a matter of debate and it need not represent a specialized DC subset. Human tolerogenic DCs generated in vitro using inhibitory cytokines, growth factors, natural immunomodulators, or genetic manipulation have been effective and several of these tolerogenic DCs are currently being tested for clinical use. Ex vivo generated tolerogenic DCs reduce activation of naïve T cells using various means, promote a variety of regulatory T cells and most importantly, frequently show stable inhibitory phenotypes upon repetitive maturation with inflammatory factors. Yet, tolerogenic DCs differ with respect to the phenotype or the number of regulatory mechanisms they employ to modulate the immune system. In our experience, tolerogenic DCs generated using the biologically active form of vitamin D (VD3-DCs), alone, or combined with dexamethasone are proficient in their immunoregulatory functions. These tolerogenic DCs show a stable maturation-resistant semi-mature phenotype with low expression of activating co-stimulatory molecules, no production of the IL-12 family of cytokines and high expression of inhibitory molecules and IL-10. VD3-DCs induce increased apoptosis of effector T cells and induce antigen-specific regulatory T cells, which work through linked suppression ensuring infectious tolerance. Lessons learned on VD3-DCs help understanding the contribution of different pattern-recognition receptors (PRRs) and secondary signals to the tolerogenic function and how a cross-talk between DCs and T cells translates into immune regulation.
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Affiliation(s)
- Tatjana Nikolic
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center Leiden, Netherlands
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