Clonal analysis of human dendritic cell progenitor using a stromal cell culture

Antigen cross-presentation by dendritic cells: A critical axis in cancer immunotherapy

Dendritic cells (DCs) are professional antigen-presenting cells that play a key role in shaping adaptive immunity. DCs have a unique ability to sample their environment, capture and process exogenous antigens into peptides that are then loaded onto major histocompatibility complex class I molecules for presentation to CD8+ T cells. This process, called cross-presentation, is essential for initiating and regulating CD8+ T cell responses against tumors and intracellular pathogens. In this review, we will discuss the role of DCs in cancer immunity, the molecular mechanisms underlying antigen cross-presentation by DCs, the immunosuppressive factors that limit the efficiency of this process in cancer, and approaches to overcome DC dysfunction and therapeutically promote antitumoral immunity.

Enhanced in vitro type 1 conventional dendritic cell generation via the recruitment of hematopoietic stem cells and early progenitors by Kit ligand

In vitro culture of bone marrow (BM) with Fms-like tyrosine kinase 3 ligand (Flt3L) is widely used to study development and function of type 1 conventional dendritic cells (cDC1). Hematopoietic stem cells (HSCs) and many progenitor populations that possess cDC1 potential in vivo do not express Flt3 and thus may not contribute to Flt3L-mediated cDC1 production in vitro. Here, we present a KitL/Flt3L protocol that recruits such HSCs and progenitors into the production of cDC1. Kit ligand (KitL) is used to expand HSCs and early progenitors lacking Flt3 expression into later stage where Flt3 is expressed. Following this initial KitL phase, a second Flt3L phase is used to support the final production of DCs. With this two-stage culture, we achieved approximately tenfold increased production of both cDC1 and cDC2 compared to Flt3L culture. cDC1 derived from this culture are similar to in vivo cDC1 in their dependence on IRF8, ability to produce IL-12, and induction of tumor regression in cDC1-deficient tumor-bearing mice. This KitL/Flt3L system for cDC1 production will be useful in further analysis of cDC1 that rely on in vitro generation from BM.

Clonal Analysis of Human Dendritic Cell Progenitors Using a Stromal Cell Culture

Dendritic cells (DCs) are a heterogenous population of professional antigen-presenting cells that play an "educator" role in immunity. Multiple DC subsets collaboratively initiate and orchestrate innate and adaptive immune responses. Recent advances in our ability to investigate cellular transcription, signaling, and function at the single-cell level have opened opportunities to examine heterogeneous populations at unprecedented resolutions. Culturing of mouse DC subsets from single bone marrow hematopoietic progenitor cells, that is, clonal analysis, has enabled identification of multiple progenitors with distinct potentials and furthered understanding of mouse DC development. However, studies of human DC development have been hampered by the lack of a corresponding system to generate multiple human DC subsets. Here, we describe a protocol to functionally profile the differentiation potentials of single human hematopoietic stem and progenitor cells (HSPCs) to multiple DC subsets, myeloid and lymphoid cells that will facilitate investigation of human DC lineage specification and reveal its molecular bases.

Application of dendritic cells in tumor immunotherapy and progress in the mechanism of anti-tumor effect of Astragalus polysaccharide (APS) modulating dendritic cells: a review

Dendritic cells (DCs) are potent antigen-presenting cells (APCs) that are essential in mediating the body's natural and adaptive immune responses. The body can regulate the function of DCs in various ways to enhance their antitumor effects. In the tumour microenvironment (TME), antigen-specific T cell responses are initiated through DC processing and delivery of tumour-associated antigens (TAAs); conversely, tumour cells inhibit DC recruitment by releasing metabolites, cytokines and other regulatory TME and function. Different subpopulations of DCs exist in tumour tissues, and their functions vary. Insight into DC subgroups in TME allows assessment of the effectiveness of tumour immunotherapy. Astragalus polysaccharide (APS) is the main component of the Chinese herb Astragalus membranaceus. The study found that the antitumor effects of APS are closely related to DCs. APS can promote the expression of surface molecules CD80 and CD86, promote the maturation of DCs, and activate CTL to exert antitumor effects. We reviewed the application of DCs in tumor immunotherapy and the mechanism of modulation of DCs by Astragalus polysaccharide to provide new directions and strategies for tumor therapy and new drug development.

Defects in Long-Term APC Repopulation Ability of Adult Human Bone Marrow Hematopoietic Stem Cells (HSCs) Compared with Fetal Liver HSCs

Immunodeficient mice reconstituted with immune systems from patients, or personalized immune (PI) mice, are powerful tools for understanding human disease. Compared with immunodeficient mice transplanted with human fetal thymus tissue and fetal liver-derived CD34⁺ cells administered i.v. (Hu/Hu mice), PI mice, which are transplanted with human fetal thymus and adult bone marrow (aBM) CD34⁺ cells, demonstrate reduced levels of human reconstitution. We characterized APC and APC progenitor repopulation in human immune system mice and detected significant reductions in blood, bone marrow (BM), and splenic APC populations in PI compared with Hu/Hu mice. APC progenitors and hematopoietic stem cells (HSCs) were less abundant in aBM CD34⁺ cells compared with fetal liver-derived CD34⁺ cell preparations, and this reduction in APC progenitors was reflected in the BM of PI compared with Hu/Hu mice 14-20 wk posttransplant. The number of HSCs increased in PI mice compared with the originally infused BM cells and maintained functional repopulation potential, because BM from some PI mice 28 wk posttransplant generated human myeloid and lymphoid cells in secondary recipients. Moreover, long-term PI mouse BM contained functional T cell progenitors, evidenced by thymopoiesis in thymic organ cultures. Injection of aBM cells directly into the BM cavity, transgenic expression of hematopoietic cytokines, and coinfusion of human BM-derived mesenchymal stem cells synergized to enhance long-term B cell and monocyte levels in PI mice. These improvements allow a sustained time frame of 18-22 wk where APCs and T cells are present and greater flexibility for modeling immune disease pathogenesis and immunotherapies in PI mice.

Dendritic cell differentiation from human induced pluripotent stem cells: challenges and progress

Dendritic cells (DCs) are the major antigen-presenting cells of the immune system responsible for initiating and coordinating immune responses. These abilities provide potential for several clinical applications, such as the development of immunogenic vaccines. However, difficulty in obtaining DCs from conventional sources, such as bone marrow (BM), peripheral blood (PBMC), and cord blood (CB), is a significantly hinders routine application. The use of human induced pluripotent stem cells (hiPSCs) is a valuable alternative for generating sufficient numbers of DCs to be used in basic and pre-clinical studies. Despite the many challenges that must be overcome to achieve an efficient protocol for obtaining the major DC types from hiPSCs, recent progress has been made. Here we review the current state of developing DCs from hiPSCs, as well as the key elements required to enable the routine use of hiPSC-derived DCs in pre-clinical and clinical assays.

Immune cells surveil aberrantly sialylated O-glycans on megakaryocytes to regulate platelet count

Immune thrombocytopenia (ITP) is a platelet disorder. Pediatric and adult ITP have been associated with sialic acid alterations, but the pathophysiology of ITP remains elusive, and ITP is often a diagnosis of exclusion. Our analysis of pediatric ITP plasma samples showed increased anti-Thomsen-Friedenreich antigen (TF antigen) antibody representation, suggesting increased exposure of the typically sialylated and cryptic TF antigen in these patients. The O-glycan sialyltransferase St3gal1 adds sialic acid specifically on the TF antigen. To understand if TF antigen exposure associates with thrombocytopenia, we generated a mouse model with targeted deletion of St3gal1 in megakaryocytes (MK) (St3gal1MK-/-). TF antigen exposure was restricted to MKs and resulted in thrombocytopenia. Deletion of Jak3 in St3gal1MK-/- mice normalized platelet counts implicating involvement of immune cells. Interferon-producing Siglec H-positive bone marrow (BM) immune cells engaged with O-glycan sialic acid moieties to regulate type I interferon secretion and platelet release (thrombopoiesis), as evidenced by partially normalized platelet count following inhibition of interferon and Siglec H receptors. Single-cell RNA-sequencing determined that TF antigen exposure by MKs primed St3gal1MK-/- BM immune cells to release type I interferon. Single-cell RNA-sequencing further revealed a new population of immune cells with a plasmacytoid dendritic cell-like signature and concomitant upregulation of the immunoglobulin rearrangement gene transcripts Igkc and Ighm, suggesting additional immune regulatory mechanisms. Thus, aberrant TF antigen moieties, often found in pathological conditions, regulate immune cells and thrombopoiesis in the BM, leading to reduced platelet count.

Unboxing dendritic cells: Tales of multi-faceted biology and function

Often referred to as the bridge between innate and adaptive immunity, dendritic cells (DCs) are professional antigen-presenting cells (APCs) that constitute a unique, yet complex cell system. Among other APCs, DCs display the unique property of inducing protective immune responses against invading microbes, or cancer cells, while safeguarding the proper homeostatic equilibrium of the immune system and maintaining self-tolerance. Unsurprisingly, DCs play a role in many diseases such as autoimmunity, allergy, infectious disease and cancer. This makes them attractive but challenging targets for therapeutics. Since their initial discovery, research and understanding of DC biology have flourished. We now recognize the presence of multiple subsets of DCs distributed across tissues. Recent studies of phenotype and gene expression at the single cell level have identified heterogeneity even within the same DC type, supporting the idea that DCs have evolved to greatly expand the flexibility of the immune system to react appropriately to a wide range of threats. This review is meant to serve as a quick and robust guide to understand the basic divisions of DC subsets and their role in the immune system. Between mice and humans, there are some differences in how these subsets are identified and function, and we will point out specific distinctions as necessary. Throughout the text, we are using both fundamental and therapeutic lens to describe overlaps and distinctions and what this could mean for future research and therapies.

Insights Into Dendritic Cells in Cancer Immunotherapy: From Bench to Clinical Applications

Dendritic cells (DCs) are efficient antigen-presenting cells (APCs) and potent activators of naïve T cells. Therefore, they act as a connective ring between innate and adaptive immunity. DC subsets are heterogeneous in their ontogeny and functions. They have proven to potentially take up and process tumor-associated antigens (TAAs). In this regard, researchers have developed strategies such as genetically engineered or TAA-pulsed DC vaccines; these manipulated DCs have shown significant outcomes in clinical and preclinical models. Here, we review DC classification and address how DCs are skewed into an immunosuppressive phenotype in cancer patients. Additionally, we present the advancements in DCs as a platform for cancer immunotherapy, emphasizing the technologies used for in vivo targeting of endogenous DCs, ex vivo generated vaccines from peripheral blood monocytes, and induced pluripotent stem cell-derived DCs (iPSC-DCs) to boost antitumoral immunity.

Inflammasomes in dendritic cells: Friend or foe?

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

Genetic models of human and mouse dendritic cell development and function

Dendritic cells (DCs) develop in the bone marrow from haematopoietic progenitors that have numerous shared characteristics between mice and humans. Human counterparts of mouse DC progenitors have been identified by their shared transcriptional signatures and developmental potential. New findings continue to revise models of DC ontogeny but it is well accepted that DCs can be divided into two main functional groups. Classical DCs include type 1 and type 2 subsets, which can detect different pathogens, produce specific cytokines and present antigens to polarize mainly naive CD8+ or CD4+ T cells, respectively. By contrast, the function of plasmacytoid DCs is largely innate and restricted to the detection of viral infections and the production of type I interferon. Here, we discuss genetic models of mouse DC development and function that have aided in correlating ontogeny with function, as well as how these findings can be translated to human DCs and their progenitors.

Inhibition of LSD1 in MDS progenitors restores differentiation of CD141Hi conventional dendritic cells

The use of immunotherapy to treat patients with myelodysplastic syndromes (MDS) shows promise but is limited by our incomplete understanding of the immunologic milieu. In solid tumors, CD141Hi conventional dendritic cells (CD141Hi cDCs) are necessary for antitumor immunosurveillance and the response to immunotherapy. Here, we found that CD141Hi cDCs are reduced in MDS bone marrow and based on the premise established in solid tumors, we hypothesized that reduced numbers of CD141Hi cDCs are associated with inferior overall survival in MDS patients. We found that MDS patients with reduced numbers of CD141Hi cDCs, but not other DC populations, showed reduced overall survival. To examine the basis for reduction in CD141Hi cDCs, we found fewer numbers of progenitors committed to DC differentiation in the MDS bone marrow and these progenitors expressed lower levels of interferon regulatory factor-8 (IRF8), a master regulator of CD141Hi cDC differentiation. To rescue impaired CD141Hi cDC differentiation, we used pharmacologic inhibition of lysine-specific demethylase 1A (LSD1) to promote CD141Hi cDC differentiation by MDS progenitors. These data reveal a previously unrecognized element of the MDS immunologic milieu. Epigenetic regulation of CD141Hi cDC differentiation offers an intriguing opportunity for intervention and a potential adjunct to immunotherapy for patients with MDS.

Transcriptional and Functional Analysis of CD1c+ Human Dendritic Cells Identifies a CD163+ Subset Priming CD8+CD103+ T Cells

Dendritic cells (DCs) are antigen-presenting cells controlling T cell activation. In humans, the diversity, ontogeny, and functional capabilities of DC subsets are not fully understood. Here, we identified circulating CD88-CD1c+CD163+ DCs (called DC3s) as immediate precursors of inflammatory CD88-CD14+CD1c+CD163+FcεRI+ DCs. DC3s develop via a specific pathway activated by GM-CSF, independent of cDC-restricted (CDP) and monocyte-restricted (cMoP) progenitors. Like classical DCs but unlike monocytes, DC3s drove activation of naive T cells. In vitro, DC3s displayed a distinctive ability to prime CD8+ T cells expressing a tissue homing signature and the epithelial homing alpha-E integrin (CD103) through transforming growth factor β (TGF-β) signaling. In vivo, DC3s infiltrated luminal breast cancer primary tumors, and DC3 infiltration correlated positively with CD8+CD103+CD69+ tissue-resident memory T cells. Together, these findings define DC3s as a lineage of inflammatory DCs endowed with a strong potential to regulate tumor immunity.

Harnessing the Complete Repertoire of Conventional Dendritic Cell Functions for Cancer Immunotherapy

The onset of checkpoint inhibition revolutionized the treatment of cancer. However, studies from the last decade suggested that the sole enhancement of T cell functionality might not suffice to fight malignancies in all individuals. Dendritic cells (DCs) are not only part of the innate immune system, but also generals of adaptive immunity and they orchestrate the de novo induction of tolerogenic and immunogenic T cell responses. Thus, combinatorial approaches addressing DCs and T cells in parallel represent an attractive strategy to achieve higher response rates across patients. However, this requires profound knowledge about the dynamic interplay of DCs, T cells, other immune and tumor cells. Here, we summarize the DC subsets present in mice and men and highlight conserved and divergent characteristics between different subsets and species. Thereby, we supply a resource of the molecular players involved in key functional features of DCs ranging from their sentinel function, the translation of the sensed environment at the DC:T cell interface to the resulting specialized T cell effector modules, as well as the influence of the tumor microenvironment on the DC function. As of today, mostly monocyte derived dendritic cells (moDCs) are used in autologous cell therapies after tumor antigen loading. While showing encouraging results in a fraction of patients, the overall clinical response rate is still not optimal. By disentangling the general aspects of DC biology, we provide rationales for the design of next generation DC vaccines enabling to exploit and manipulate the described pathways for the purpose of cancer immunotherapy in vivo. Finally, we discuss how DC-based vaccines might synergize with checkpoint inhibition in the treatment of malignant diseases.

Dendritic cell development at a clonal level within a revised 'continuous' model of haematopoiesis

Understanding development of the dendritic cell (DC) subtypes continues to evolve. The origin and relationship of conventional DC type 1 (cDC1), cDC type 2 (cDC2) and plasmacytoid DCs (pDCs) to each other, and in relation to classic myeloid and lymphoid cells, has had a long and controversial history and is still not fully resolved. This review summarises the technological developments and findings that have been achieved at a clonal level, and how that has enhanced our knowledge of the process. It summarises the single cell lineage tracing technologies that have emerged, their application in in vitro and in vivo studies, in both mouse and human settings, and places the findings in a wider context of understanding haematopoiesis at a single cell or clonal level. In particular, it addresses the fate heterogeneity observed in many phenotypically defined progenitor subsets and how these findings have led to a departure from the classic ball-and-stick models of haematopoiesis to the emerging continuous model. Prior contradictions in DC development may be reconciled if they are framed within this revised model, where commitment to a lineage or cell type does not occur in an all-or-nothing process in defined progenitors but rather can occur at many stages of haematopoiesis in a dynamic process.

The quest for faithful in vitro models of human dendritic cells types

Dendritic cells (DCs) are mononuclear phagocytes that are specialized in the induction and functional polarization of effector lymphocytes, thus orchestrating immune defenses against infections and cancer. The population of DC encompasses distinct cell types that vary in their efficacy for complementary functions and are thus likely involved in defending the body against different threats. Plasmacytoid DCs specialize in the production of high levels of the antiviral cytokines type I interferons. Type 1 conventional DCs (cDC1s) excel in the activation of cytotoxic CD8⁺ T cells (CTLs) which are critical for defense against cancer and infections by intracellular pathogens. Type 2 conventional DCs (cDC2s) prime helper CD4⁺ T cells for the production of type 2 cytokines underpinning immune defenses against worms or of IL-17 promoting control of infections by extracellular bacteria or fungi. Hence, clinically manipulating the development and functions of DC types could have a major impact for improving treatments against many diseases. However, the rarity and fragility of human DC types is impeding advancement towards this goal. To overcome this roadblock, major efforts are ongoing to generate in vitro large numbers of distinct human DC types. We review here the current state of this research field, emphasizing recent breakthrough and proposing future priorities. We also pinpoint the necessity to develop a consensus nomenclature and rigorous methodologies to ensure proper identification and characterization of human DC types. Finally, we elaborate on how faithful in vitro models of human DC types can accelerate our understanding of the biology of these cells and the engineering of next generation vaccines or immunotherapies against viral infections or cancer.

Recent advances towards deciphering human dendritic cell development

Dendritic cell (DC) populations are the orchestrators of immune responses and arise from hematopoietic progenitors. Studies to unravel DC ontogeny have been conducted mainly in mice due to historical and practical reasons. However, understanding DC development in humans is a prerequisite for manipulating this process for therapeutic design. Here, we review the advantages and limitations of methods used to study human DC development in vitro and in vivo. In particular, we examine the in vitro culture systems that support the differentiation of all or some DC subpopulations. We also review recent discoveries regarding human DC precursors and factors that regulate their differentiation.

Transcriptional control of dendritic cell development and functions

Dendritic cells (DCs) are major regulators of adaptive immunity, as they are not only capable to induce efficient immune responses, but are also crucial to maintain peripheral tolerance and thereby inhibit autoimmune reactions. DCs bridge the innate and the adaptive immune system by presenting peptides of self and foreign antigens as peptide MHC complexes to T cells. These properties render DCs as interesting target cells for immunomodulatory therapies in cancer, but also autoimmune diseases. Several subsets of DCs with special properties and functions have been described. Recent achievements in understanding transcriptional programs on single cell level, together with the generation of new murine models targeting specific DC subsets, advanced our current understanding of DC development and function. Thus, DCs arise from precursor cells in the bone marrow with distinct progenitor cell populations splitting the monocyte populations and macrophage populations from the DC lineage, which upon lineage commitment can be separated into conventional cDC1, cDC2, and plasmacytoid DCs (pDCs). The DC populations harbor intrinsic programs enabling them to react for specific pathogens in dependency on the DC subset, and thereby orchestrate T cell immune responses. Similarities, but also varieties, between human and murine DC subpopulations are challenging, and will require further investigation of human specimens under consideration of the influence of the tissue micromilieu and DC subset localization in the future.

Origin and development of classical dendritic cells

Classical dendritic cells (cDCs) are mononuclear phagocytes of hematopoietic origin specialized in the induction and regulation of adaptive immunity. Initially defined by their unique T cell activation potential, it became quickly apparent that cDCs would be difficult to distinguish from other phagocyte lineages, by solely relying on marker-based approaches. Today, cDCs definition increasingly embed their unique ontogenetic features. A growing consensus defines cDCs on multiple criteria including: (1) dependency on the fms-like tyrosine kinase 3 ligand hematopoietic growth factor, (2) development from the common DC bone marrow progenitor, (3) constitutive expression of the transcription factor ZBTB46 and (4) the ability to induce, after adequate stimulation, the activation of naïve T lymphocytes. cDCs are a heterogeneous cell population that contains two main subsets, named type 1 and type 2 cDCs, arising from divergent ontogenetic pathways and populating multiple lymphoid and non-lymphoid tissues. Here, we present recent knowledge on the cellular and molecular pathways controlling the specification and commitment of cDC subsets from murine and human hematopoietic stem cells.

Airway Macrophage and Dendritic Cell Subsets in the Resting Human Lung

Dendritic cells (DCs) and macrophages (MΦs) are antigen-presenting phagocytic cells found in many peripheral tissues of the human body, including the blood, lymph nodes, skin, and lung. They are vital to maintaining steady-state respiration in the human lung based on their ability to clear airways while also directing tolerogenic or inflammatory responses based on specific stimuli. Over the past three decades, studies have determined that there are multiple subsets of these two general cell types that exist in the airways and interstitium. Identifying these numerous subsets has proven challenging, especially with the unique microenvironments present in the lung. Cells found in the vasculature are not the same subsets found in the skin or the lung, as demonstrated by surface marker expression. By transcriptional profiling, these subsets show similarities but also major differences. Primary human lung cells and/ or tissues are difficult to acquire, particularly in a healthy condition. Additionally, surface marker screening and transcriptional profiling are continually identifying new DC and MΦ subsets. While the overall field is moving forward, we emphasize that more attention needs to focus on replicating the steady-state microenvironment of the lung to reveal the physiological functions of these subsets.

Biology and prognostic impact of clonal plasmacytoid dendritic cells in chronic myelomonocytic leukemia

Islands of CD123^high cells have been commonly described in the bone marrow of patients with chronic myelomonocytic leukemia (CMML). Using a multiparameter flow cytometry assay, we detected an excess of CD123⁺ mononucleated cells that are lineage-negative, CD45⁺, CD11c^-, CD33^-, HLA-DR⁺, BDCA-2⁺, BDCA-4⁺ in the bone marrow of 32/159 (20%) patients. Conventional and electron microscopy, flow cytometry detection of cell surface markers, gene expression analyses, and the ability to synthesize interferon alpha in response to Toll-like receptor agonists identified these cells as bona fide plasmacytoid dendritic cells (pDCs). Whole-exome sequencing of sorted monocytes and pDCs identified somatic mutations in genes of the oncogenic RAS pathway in the two cell types of every patient. CD34⁺ cells could generate high amount of pDCs in the absence of FMS-like tyrosine kinase 3-ligand (FLT3L). Finally, an excess of pDCs correlates with regulatory T cell accumulation and an increased risk of acute leukemia transformation. These results demonstrate the FLT3L-independent accumulation of clonal pDCs in the bone marrow of CMML patients with mutations affecting the RAS pathway, which is associated with a higher risk of disease progression.

Human Dendritic Cells: Their Heterogeneity and Clinical Application Potential in Cancer Immunotherapy

Dendritic cells (DC) are professional antigen presenting cells, uniquely able to induce naïve T cell activation and effector differentiation. They are, likewise, involved in the induction and maintenance of immune tolerance in homeostatic conditions. Their phenotypic and functional heterogeneity points to their great plasticity and ability to modulate, according to their microenvironment, the acquired immune response and, at the same time, makes their precise classification complex and frequently subject to reviews and improvement. This review will present general aspects of the DC physiology and classification and will address their potential and actual uses in the management of human disease, more specifically cancer, as therapeutic and monitoring tools. New combination treatments with the participation of DC will be also discussed.

High Dimensional Functionomic Analysis of Human Hematopoietic Stem and Progenitor Cells at a Single Cell Level

The ability to conduct investigation of cellular transcription, signaling, and function at the single-cell level has opened opportunities to examine heterogeneous populations at unprecedented resolutions. Although methods have been developed to evaluate high-dimensional transcriptomic and proteomic data (relating to cellular mRNA and protein), there has not been a method to evaluate corresponding high-dimensional functionomic data (relating to cellular functions) from single cells. Here, we present a protocol to quantitatively measure the differentiation potentials of single human hematopoietic stem and progenitor cells, and then cluster the cells according to these measurements. High dimensional functionomic analysis of cell potential allows cell function to be linked to molecular mechanisms within the same progenitor population.

Dendritic cell-based immunotherapy

Immunotherapy using dendritic cell (DC)-based vaccination is an approved approach for harnessing the potential of a patient's own immune system to eliminate tumor cells in metastatic hormone-refractory cancer. Overall, although many DC vaccines have been tested in the clinic and proven to be immunogenic, and in some cases associated with clinical outcome, there remains no consensus on how to manufacture DC vaccines. In this review we will discuss what has been learned thus far about human DC biology from clinical studies, and how current approaches to apply DC vaccines in the clinic could be improved to enhance anti-tumor immunity.

Dendritic cell development-History, advances, and open questions

Dendritic cells (DCs) are uniquely potent in orchestrating T cell immune response, thus they are indispensable immune sentinels. They originate from progenitors in the bone marrow through hematopoiesis, a highly regulated developmental process involving multiple cellular and molecular events. This review highlights studies of DC development-from the discovery of DCs as glass-adherent antigen presenting cells to the debate and resolution of their origin and lineage map. In particular, we summarize the roles of lineage-specific cytokines, the placement of distinct hematopoietic progenitors within the DC lineage and transcriptional programs governing DC development, which together have allowed us to diagram the current view of DC hematopoiesis. Important open questions and debates on the DC development and relevant models are also discussed.

The Alternative Faces of Macrophage Generate Osteoclasts

The understanding of how osteoclasts are generated and whether they can be altered by inflammatory stimuli is a topic of particular interest for osteoclastogenesis. It is known that the monocyte/macrophage lineage gives rise to osteoclasts (OCs) by the action of macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-kB ligand (RANKL), which induce cell differentiation through their receptors, c-fms and RANK, respectively. The multinucleated giant cells (MGCs) generated by the engagement of RANK/RANKL are typical OCs. Nevertheless, very few studies have addressed the question of which subset of macrophages generates OCs. Indeed, two main subsets of macrophages are postulated, the inflammatory or classically activated type (M1) and the anti-inflammatory or alternatively activated type (M2). It has been proposed that macrophages can be polarized in vitro towards a predominantly M1 or M2 phenotype with the addition of granulocyte macrophage- (GM-) CSF or M-CSF, respectively. Various inflammatory stimuli known to induce macrophage polarization, such as LPS or TNF-α, can alter the type of MGC obtained from RANKL-induced differentiation. This review aims to highlight the role of immune-related stimuli and factors in inducing macrophages towards the osteoclastogenesis choice.