CD16+ and CD16- human blood monocyte subsets differentiate in vitro to dendritic cells with different abilities to stimulate CD4+ T cells

Inflammatory and tolerogenic myeloid cells determine outcome following human allergen challenge

Innate mononuclear phagocytic system (MPS) cells preserve mucosal immune homeostasis. We investigated their role at nasal mucosa following allergen challenge with house dust mite. We combined single-cell proteome and transcriptome profiling on nasal immune cells from nasal biopsies cells from 30 allergic rhinitis and 27 non-allergic subjects before and after repeated nasal allergen challenge. Biopsies of patients showed infiltrating inflammatory HLA-DRhi/CD14+ and CD16+ monocytes and proallergic transcriptional changes in resident CD1C+/CD1A+ conventional dendritic cells (cDC)2 following challenge. In contrast, non-allergic individuals displayed distinct innate MPS responses to allergen challenge: predominant infiltration of myeloid-derived suppressor cells (MDSC: HLA-DRlow/CD14+ monocytes) and cDC2 expressing inhibitory/tolerogenic transcripts. These divergent patterns were confirmed in ex vivo stimulated MPS nasal biopsy cells. Thus, we identified not only MPS cell clusters involved in airway allergic inflammation but also highlight novel roles for non-inflammatory innate MPS responses by MDSC to allergens in non-allergic individuals. Future therapies should address MDSC activity as treatment for inflammatory airway diseases.

Origin of Osteoclasts: Osteoclast Precursor Cells

Osteoclasts are multinucleated bone-resorbing cells and a key player in bone remodeling for health and disease. Since the discovery of osteoclasts in 1873, the structure and function of osteoclasts and the molecular and cellular mechanisms of osteoclastogenesis have been extensively studied. Moreover, it has been well established that osteoclasts are differentiated in vitro from myeloid cells such as bone marrow macrophages or monocytes. The concept showing that osteoclasts are derived from a specific population (named osteoclast precursor cells [OCPs]) among myeloid cells has been long hypothesized. However, the specific precursor population of osteoclasts is not clearly defined yet. A growing body of work provides evidence of the developmental origin and lifespan of murine osteoclasts, particularly in vivo. Here, we review the emerging evidence that supports the existence of OCPs and discuss current insights into their identity.

Classical DC2 subsets and monocyte-derived DC: Delineating the developmental and functional relationship

To specifically tailor immune responses to a given pathogenic threat, dendritic cells (DC) are highly heterogeneous and comprise many specialized subtypes, including conventional DC (cDC) and monocyte-derived DC (MoDC), each with distinct developmental and functional characteristics. However, the functional relationship between cDC and MoDC is not fully understood, as the overlapping phenotypes of certain type 2 cDC (cDC2) subsets and MoDC do not allow satisfactory distinction of these cells in the tissue, particularly during inflammation. However, precise cDC2 and MoDC classification is required for studies addressing how these diverse cell types control immune responses and is therefore currently one of the major interests in the field of cDC research. This review will revise murine cDC2 and MoDC biology in the steady state and under inflammatory conditions and discusses the commonalities and differences between ESAM^lo cDC2, inflammatory cDC2, and MoDC and their relative contribution to the initiation, propagation, and regulation of immune responses.

Vitamin D-Dimer: A Possible Biomolecule Modulator in Cytotoxic and Phagocytosis Processes?

Background: Vitamin D3 complexed to deglycosylated vitamin D binding protein (VitD-dgVDBP) is a water-soluble vitamin D dimeric compound (VitD-dgVDBP). It is not clear how VitD-dgVDBP affects circulating monocytes, macrophages, other immune cell systems, including phagocytosis and apoptosis, and the generation of reactive oxygen species (ROS) compared to dgVDBP. Methods: Flow cytometry was used to measure superoxide anion radical (O2*−) levels and macrophage activity in the presence of VitD-dgVDBP or dgVDBP. VitD-dgVDBP was incubated with normal human lymphocytes (nPBMCs), and several clusters of determination (CDs) were estimated. dgVDBP and VitD-dgVDBP apoptosis was estimated on malignant prostatic cells. Results: The macrophage activity was 2.8-fold higher using VitD-dgVDBP (19.8·106 counts) compared to dgVDBP (7.0·106 counts), but O2*− production was 1.8-fold lower in favor of VitD-dgVDBP (355·103 counts) compared to dgVDBP (630·106 counts). The calculated ratio of the radical/macrophage activity was 5-fold lower compared to that of dgVDBP. Only VitD-dgVDBP activated caspase-3 (8%), caspase-9 (13%), and cytochrome-C (11%) on prostatic cancer cells. PE-Cy7-labeled VitD-dgVDBP was found to bind to cytotoxic suppressor cells, monocytes/macrophages, dendritic and natural killer cells (CD8+), and helper cells (CD4+). After 12 h of co-incubation of nPBMCs with VitD-dgVDBP, significant activation and expression were measured for CD16++/CD16 (0.6 ± 0.1% vs. 0.4 ± 0.1%, p < 0.05), CD45k+ (96.0 ± 6.0% vs. 84.7 ± 9.5%, p < 0.05), CD85k+ (24.3 ± 13.2% vs. 3.8 ± 3.2%, p < 0.05), and CD85k+/CD123+ (46.8 ± 8.1% vs. 3.5 ± 3.7%, p < 0.001) compared to the control experiment. No significant difference was found using CD3+, CD4+, CD8+, CD4/CD8, CD4/CD8, CD16+, CD16++, CD14+, or CD123+. A significant decline in CD14+/CD16+ was obtained in the presence of VitD-dgVDBP (0.7 ± 0.2% vs. 3.1 ± 1.7%; p < 0.01). Conclusion: The newly developed water-soluble VitD3 form VitD-dgVDBP affected cytotoxic suppressor cells by activating the low radical-dependent CD16 pathway and seemed to induce apoptosis in malignant prostatic cells.

CyTOF Profiling of Zika and Dengue Virus-Infected Human Peripheral Blood Mononuclear Cells Identifies Phenotypic Signatures of Monotype Subsets and Upregulation of the Interferon-Inducible Protein CD169

Zika and dengue virus (ZIKV and DENV) are two flaviviruses responsible for important vector-borne emerging infectious diseases. While there have been multiple DENV epidemics in the last decades, there have been fewer documented epidemics caused by ZIKV until recent years. Thus, our current knowledge about the biology of ZIKV, the disease, and the immune responses in humans is limited. Here, we used mass cytometry (CyTOF) to perform a detailed characterization of the innate immune responses elicited by ZIKV and DENV in human peripheral blood mononuclear cells (PBMCs) from healthy donors infected ex vivo. We found that ZIKV and DENV exposure of human PBMCs induces global phenotypic changes in myeloid cells, characterized mainly by upregulation of costimulatory molecules (CD86 and CD40), CD38, and the type I interferon-inducible protein CD169, a marker for phagocytic function and cross-priming potential in myeloid cells. We also found that ZIKV induces expansion of nonclassical monocytes in cell culture. The analysis of the phenotype of the three monocyte subtypes (classical, intermediate, and nonclassical) at the single-cell level identified differences in their expression of CD86, CD38, CXCL8, and CXCL10 during ZIKV and DENV infection. Overall, using CyTOF, we found that ex vivo infections of PBMCs with ZIKV and DENV reproduced many aspects of the profile found in blood from patients in previously described cohort studies, which highlights the suitability of this system for the study of the human host responses to these viruses. IMPORTANCE Zika and dengue viruses are emergent arboviruses of great public health impact. Both viruses are responsible for important diseases, yet there is currently no vaccine or specific treatment available. Immune cells play critical roles in the virus cycle as well as in the innate and adaptive immune response elicited in the host; therefore, it is critical to understand the changes induced by virus infection in peripheral blood mononuclear cells (PBMCs). In this study, we used a model of ex vivo infection of PBMCs and CyTOF technology to profile the early innate immune changes induced by Zika virus and dengue virus in blood.

RALDH Activity Induced by Bacterial/Fungal Pathogens in CD16+ Monocyte-Derived Dendritic Cells Boosts HIV Infection and Outgrowth in CD4+ T Cells

HIV reservoirs persist in gut-homing CD4⁺ T cells of people living with HIV and receiving antiretroviral therapy, but the antigenic specificity of such reservoirs remains poorly documented. The imprinting for gut homing is mediated by retinoic acid (RA), a vitamin A-derived metabolite produced by dendritic cells (DCs) exhibiting RA-synthesizing (RALDH) activity. RALDH activity in DCs can be induced by TLR2 ligands, such as bacterial peptidoglycans and fungal zymosan. Thus, we hypothesized that bacterial/fungal pathogens triggering RALDH activity in DCs fuel HIV reservoir establishment/outgrowth in pathogen-reactive CD4⁺ T cells. Our results demonstrate that DCs derived from intermediate/nonclassical CD16⁺ compared with classical CD16^- monocytes exhibited superior RALDH activity and higher capacity to transmit HIV infection to autologous Staphylococcus aureus-reactive T cells. Exposure of total monocyte-derived DCs (MDDCs) to S. aureus lysates as well as TLR2 (zymosan and heat-killed preparation of Listeria monocytogenes) and TLR4 (LPS) agonists but not CMV lysates resulted in a robust upregulation of RALDH activity. MDDCs loaded with S. aureus or zymosan induced the proliferation of T cells with a CCR5⁺integrin β7⁺CCR6⁺ phenotype and efficiently transmitted HIV infection to these T cells via RALDH/RA-dependent mechanisms. Finally, S. aureus- and zymosan-reactive CD4⁺ T cells of antiretroviral therapy-treated people living with HIV carried replication-competent integrated HIV-DNA, as demonstrated by an MDDC-based viral outgrowth assay. Together, these results support a model in which bacterial/fungal pathogens in the gut promote RALDH activity in MDDCs, especially in CD16⁺ MDDCs, and subsequently imprint CD4⁺ T cells with gut-homing potential and HIV permissiveness. Thus, nonviral pathogens play key roles in fueling HIV reservoir establishment/outgrowth via RALDH/RA-dependent mechanisms that may be therapeutically targeted.

Neonatal monocytes demonstrate impaired homeostatic extravasation into a microphysiological human vascular model

Infections are most frequent at the extremes of life, especially among newborns, reflecting age-specific differences in immunity. Monocytes maintain tissue-homeostasis and defence-readiness by escaping circulation in the absence of inflammation to become tissue-resident antigen presenting cells in vivo. Despite equivalent circulating levels, neonates demonstrate lower presence of monocytes inside peripheral tissues as compared to adults. To study the ability of monocytes to undergo autonomous transendothelial extravasation under biologically accurate circumstances we engineered a three-dimensional human vascular-interstitial model including collagen, fibronectin, primary endothelial cells and autologous untreated plasma. This microphysiological tissue construct enabled age-specific autonomous extravasation of monocytes through a confluent human endothelium in the absence of exogenous chemokines and activation. Both CD16- and CD16+ newborn monocytes demonstrated lower adherence and extravasation as compared to adults. In contrast, pre-activated tissue constructs were colonized by newborn monocytes at the same frequency than adult monocytes, suggesting that neonatal monocytes are capable of colonizing inflamed tissues. The presence of autologous plasma neither improved newborn homeostatic extravasation nor shaped age-specific differences in endothelial cytokines that could account for this impairment. Newborn monocytes demonstrated significantly lower surface expression of CD31 and CD11b, and mechanistic experiments using blocking antibodies confirmed a functional role for CD31 and CD54 in neonatal homeostatic extravasation. Our data suggests that newborn monocytes are intrinsically impaired in extravasation through quiescent endothelia, a phenomenon that could contribute to the divergent immune responsiveness to vaccines and susceptibility to infection observed during early life.

Monocytopenia, monocyte morphological anomalies and hyperinflammation characterise severe COVID-19 in type 2 diabetes

Early in the COVID-19 pandemic, type 2 diabetes (T2D) was marked as a risk factor for severe disease and mortality. Inflammation is central to the aetiology of both conditions where variations in immune responses can mitigate or aggravate disease course. Identifying at-risk groups based on immunoinflammatory signatures is valuable in directing personalised care and developing potential targets for precision therapy. This observational study characterised immunophenotypic variation associated with COVID-19 severity in T2D. Broad-spectrum immunophenotyping quantified 15 leucocyte populations in peripheral circulation from a cohort of 45 hospitalised COVID-19 patients with and without T2D. Lymphocytopenia and specific loss of cytotoxic CD8+ lymphocytes were associated with severe COVID-19 and requirement for intensive care in both non-diabetic and T2D patients. A morphological anomaly of increased monocyte size and monocytopenia restricted to classical CD14Hi CD16- monocytes was specifically associated with severe COVID-19 in patients with T2D requiring intensive care. Increased expression of inflammatory markers reminiscent of the type 1 interferon pathway (IL6, IL8, CCL2, INFB1) underlaid the immunophenotype associated with T2D. These immunophenotypic and hyperinflammatory changes may contribute to increased voracity of COVID-19 in T2D. These findings allow precise identification of T2D patients with severe COVID-19 as well as provide evidence that the type 1 interferon pathway may be an actionable therapeutic target for future studies.

Identification of a DNA Aptamer That Binds to Human Monocytes and Macrophages

As cancer strategies shift toward immunotherapy, the need for new binding ligands to target and isolate specific immune cell populations has soared. Based on prior work identifying a peptide specific for murine M2-like macrophages, we sought to identify an aptamer that could bind human M2-like macrophages. Tumor-associated macrophages (TAMs) adopt an M2-like phenotype and support tumor progression and dissemination. Here, we employed cell-SELEX to identify an aptamer ligand that targets this cell population over tissue resident (M0-like) or tumoricidal (M1-like) macrophages. Instead, we identified an aptamer that binds both human M0- and M2-like macrophages and monocytes, with highest binding affinity to M2-like macrophage (K_d ∼ 20 nM) and monocytes (K_d ∼ 45 nM) and minimal binding to other leukocytes. The aptamer binds to CD14⁺ but not CD16⁺ monocytes, and is rapidly internalized by these cells. We also demonstrate that this aptamer is able to bind human monocytes when both are administered in vivo to mice. Thus, binding to these cell populations (monocytes, M0-like and M2-like macrophages), this aptamer lends itself toward monocyte-specific applications, such as monocyte-targeted drug delivery or column selection.

Fractalkine/CX3CL1 in Neoplastic Processes

Fractalkine/CX3C chemokine ligand 1 (CX3CL1) is a chemokine involved in the anticancer function of lymphocytes-mainly NK cells, T cells and dendritic cells. Its increased levels in tumors improve the prognosis for cancer patients, although it is also associated with a poorer prognosis in some types of cancers, such as pancreatic ductal adenocarcinoma. This work focuses on the 'hallmarks of cancer' involving CX3CL1 and its receptor CX3CR1. First, we describe signal transduction from CX3CR1 and the role of epidermal growth factor receptor (EGFR) in this process. Next, we present the role of CX3CL1 in the context of cancer, with the focus on angiogenesis, apoptosis resistance and migration and invasion of cancer cells. In particular, we discuss perineural invasion, spinal metastasis and bone metastasis of cancers such as breast cancer, pancreatic cancer and prostate cancer. We extensively discuss the importance of CX3CL1 in the interaction with different cells in the tumor niche: tumor-associated macrophages (TAM), myeloid-derived suppressor cells (MDSC) and microglia. We present the role of CX3CL1 in the development of active human cytomegalovirus (HCMV) infection in glioblastoma multiforme (GBM) brain tumors. Finally, we discuss the possible use of CX3CL1 in immunotherapy.

Predicting worse survival for newly diagnosed T cell lymphoma based on the decreased baseline CD16-/CD16 + monocyte ratio

T cell non-Hodgkin lymphoma (T-NHL) is highly invasive and heterogeneous without accurate prognosis prediction. We proposed peripheral CD16-/CD16 + monocytes the additional indicators for T-NHL prognosis. We prospectively recruited 31 T-NHL patients without previous treatment. The CD16-/CD16 + monocyte ratio before chemotherapy was calculated and regular follow up was performed to calculate prognostic prediction value. Tumor associated macrophages (TAM) in tumor tissue were counted and transcriptome sequencing of CD16- and CD16 + monocytes was applied to explore potential mechanisms. We found that T-NHL patients had higher ratio of total monocytes especially the CD16 + monocytes along with a decreased ratio of CD16-/CD16 + monocytes, compared to the health control. The 1-year overall survival rate was 0.492 and 0.755 for CD16- monocyte/CD16 + monocyte ratio of <11 and ≥11(p < 0.05), respectively. The peripheral CD16-/CD16 + monocyte ratio was significantly relevant with the pathological CD68/CD206 macrophage ratio. The differently expressed genes in CD16- and CD16 + monocytes from T-NHL patients were mainly involved in signaling molecules related to tumor microenvironment. Pro-tumor genes were identified in monocyte subsets especially in CD16 + monocytes. In conclusion, the ratio of peripheral CD16-/CD16 + monocyte helps to stratify the prognosis of T-NHL. The relatively increased CD16 + monocytes may contribute to the pro-tumor microenvironment of T-NHL.

Mass Cytometry and Single-Cell RNA-seq Profiling of the Heterogeneity in Human Peripheral Blood Mononuclear Cells Interacting with Silver Nanoparticles

Understanding the interactions between nanoparticles (NPs) and human immune cells is necessary for justifying their utilization in consumer products and biomedical applications. However, conventional assays may be insufficient in describing the complexity and heterogeneity of cell-NP interactions. Herein, mass cytometry and single-cell RNA-sequencing (scRNA-seq) are complementarily used to investigate the heterogeneous interactions between silver nanoparticles (AgNPs) and primary immune cells. Mass cytometry reveals the heterogeneous biodistribution of the positively charged polyethylenimine-coated AgNPs in various cell types and finds that monocytes and B cells have higher association with the AgNPs than other populations. scRNA-seq data of these two cell types demonstrate that each type has distinct responses to AgNP treatment: NRF2-mediated oxidative stress is confined to B cells, whereas monocytes show Fcγ-mediated phagocytosis. Besides the between-population heterogeneity, analysis of single-cell dose-response relationships further reveals within-population diversity for the B cells and naïve CD4⁺ T cells. Distinct subsets having different levels of cellular responses with respect to their cellular AgNP doses are found. This study demonstrates that the complementary use of mass cytometry and scRNA-seq is helpful for gaining in-depth knowledge on the heterogeneous interactions between immune cells and NPs and can be incorporated into future toxicity assessments of nanomaterials.

Improving immunological insights into the ferret model of human viral infectious disease

Ferrets are a well-established model for studying both the pathogenesis and transmission of human respiratory viruses and evaluation of antiviral vaccines. Advanced immunological studies would add substantial value to the ferret models of disease but are hindered by the low number of ferret-reactive reagents available for flow cytometry and immunohistochemistry. Nevertheless, progress has been made to understand immune responses in the ferret model with a limited set of ferret-specific reagents and assays. This review examines current immunological insights gained from the ferret model across relevant human respiratory diseases, with a focus on influenza viruses. We highlight key knowledge gaps that need to be bridged to advance the utility of ferrets for immunological studies.

CD16+ monocytes give rise to CD103+RALDH2+TCF4+ dendritic cells with unique transcriptional and immunological features

Classical CD16^- vs intermediate/nonclassical CD16⁺ monocytes differ in their homing potential and biological functions, but whether they differentiate into dendritic cells (DCs) with distinct contributions to immunity against bacterial/viral pathogens remains poorly investigated. Here, we employed a systems biology approach to identify clinically relevant differences between CD16⁺ and CD16^- monocyte-derived DCs (MDDCs). Although both CD16⁺ and CD16^- MDDCs acquire classical immature/mature DC markers in vitro, genome-wide transcriptional profiling revealed unique molecular signatures for CD16⁺ MDDCs, including adhesion molecules (ITGAE/CD103), transcription factors (TCF7L2/TCF4), and enzymes (ALDH1A2/RALDH2), whereas CD16^- MDDCs exhibit a CDH1/E-cadherin⁺ phenotype. Of note, lipopolysaccharides (LPS) upregulated distinct transcripts in CD16⁺ (eg, CCL8, SIGLEC1, MIR4439, SCIN, interleukin [IL]-7R, PLTP, tumor necrosis factor [TNF]) and CD16^- MDDCs (eg, MMP10, MMP1, TGM2, IL-1A, TNFRSF11A, lysosomal-associated membrane protein 1, MMP8). Also, unique sets of HIV-modulated genes were identified in the 2 subsets. Further gene set enrichment analysis identified canonical pathways that pointed to "inflammation" as the major feature of CD16⁺ MDDCs at immature stage and on LPS/HIV exposure. Finally, functional validations and meta-analysis comparing the transcriptome of monocyte and MDDC subsets revealed that CD16⁺ vs CD16^- monocytes preserved their superior ability to produce TNF-α and CCL22, as well as other sets of transcripts (eg, TCF4), during differentiation into DC. These results provide evidence that monocyte subsets are transcriptionally imprinted/programmed with specific differentiation fates, with intermediate/nonclassical CD16⁺ monocytes being precursors for pro-inflammatory CD103⁺RALDH2⁺TCF4⁺ DCs that may play key roles in mucosal immunity homeostasis/pathogenesis. Thus, alterations in the CD16⁺ /CD16^- monocyte ratios during pathological conditions may dramatically influence the quality of MDDC-mediated immunity.

An Anticancer Drug Cocktail of Three Kinase Inhibitors Improved Response to a Dendritic Cell-Based Cancer Vaccine

Monocyte-derived dendritic cell (moDC)-based cancer therapies intended to elicit antitumor T-cell responses have limited efficacy in most clinical trials. However, potent and sustained antitumor activity in a limited number of patients highlights the therapeutic potential of moDCs. In vitro culture conditions used to generate moDCs can be inconsistent, and moDCs generated in vitro are less effective than natural DCs. On the basis of our study highlighting the ability for certain kinase inhibitors to enhance tumor antigenicity, we therefore screened kinase inhibitors for their ability to improve DC immunogenicity. We identified AKT inhibitor MK2206, DNA-PK inhibitor NU7441, and MEK inhibitor trametinib as the compounds most effective at modulating moDC immunogenicity. The combination of these drugs, referred to as MKNUTRA, enhanced moDC activity over treatment with individual drugs while exhibiting minimal toxicity. An evaluation of 335 activation and T-cell-suppressive surface proteins on moDCs revealed that MKNUTRA treatment more effectively matured cells and reduced the expression of tolerogenic proteins as compared with control moDCs. MKNUTRA treatment imparted to ICT107, a glioblastoma (GBM) DC-based vaccine that has completed phase II trials, an increased ability to stimulate patient-derived autologous CD8+ T cells against the brain tumor antigens IL13Rα2(345-354) and TRP2(180-188) In vivo, treating ICT107 with MKNUTRA, prior to injection into mice with an established GBM tumor, reduced tumor growth kinetics. This response was associated with an increased frequency of tumor-reactive lymphocytes within tumors and in peripheral tissues. These studies broaden the application of targeted anticancer drugs and highlight their ability to increase moDC immunogenicity.

Using Dendritic Cell-Based Immunotherapy to Treat HIV: How Can This Strategy be Improved?

Harnessing dendritic cells (DC) to treat HIV infection is considered a key strategy to improve anti-HIV treatment and promote the discovery of functional or sterilizing cures. Although this strategy represents a promising approach, the results of currently published trials suggest that opportunities to optimize its performance still exist. In addition to the genetic and clinical characteristics of patients, the efficacy of DC-based immunotherapy depends on the quality of the vaccine product, which is composed of precursor-derived DC and an antigen for pulsing. Here, we focus on some factors that can interfere with vaccine production and should thus be considered to improve DC-based immunotherapy for HIV infection.

Microphysiologic Human Tissue Constructs Reproduce Autologous Age-Specific BCG and HBV Primary Immunization in vitro

Current vaccine development disregards human immune ontogeny, relying on animal models to select vaccine candidates targeting human infants, who are at greatest risk of infection worldwide, and receive the largest number of vaccines. To help accelerate and de-risk development of early-life effective immunization, we engineered a human age-specific microphysiologic vascular-interstitial interphase, suitable for pre-clinical modeling of distinct age-targeted immunity in vitro. Our Tissue Constructs (TCs) enable autonomous extravasation of monocytes that undergo rapid self-directed differentiation into migratory Dendritic Cells (DCs) in response to adjuvants and licensed vaccines such as Bacille Calmette-Guérin (BCG) or Hepatitis B virus Vaccine (HBV). TCs contain a confluent human endothelium grown atop a tri-dimensional human extracellular matrix substrate, employ human age-specific monocytes and autologous non heat-treated plasma, and avoid the use of xenogenic materials and exogenous cytokines. Vaccine-pulsed TCs autonomously generated DCs that induced single-antigen recall responses from autologous naïve and memory CD4+ T lymphocytes, matching study participant immune-status, including BCG responses paralleling donor PPD status, BCG-induced adenosine deaminase (ADA) activity paralleling infant cohorts in vivo, and multi-dose HBV antigen-specific responses as demonstrated by lymphoproliferation and TCR sequencing. Overall, our microphysiologic culture method reproduced age- and antigen-specific recall responses to BCG and HBV immunization, closely resembling those observed after a birth immunization of human cohorts in vivo, offering for the first time a new approach to early pre-clinical selection of effective age-targeted vaccine candidates.

Subcutaneous immunotherapy induces alterations in monocytes and dendritic cells homeostasis in allergic rhinitis patients

Background

Specific subcutaneous immunotherapy (SCIT) can achieve long-term remission in patients with allergic rhinitis (AR) through complex and still unknown mechanisms. The aim of this study is to evaluate the effect of SCIT over CD16⁺ and CD16⁻ monocytes, myeloid (mDCs) and plasmacytoid dendritic cells (pDCs) in patients with AR, comparatively to pharmacological standard treatment (non-SIT).

Methods

The relative frequency and absolute number of monocytes and DC subsets, the frequency of these cells producing TNFα after in vitro stimulation with Dermatophagoides pteronyssinus (Dpt) extract, and the expression levels of receptor-bound IgE or IgG were assessed by flow cytometry, in peripheral blood samples from 23 healthy individuals (HG) and 43 participants with AR mono-sensitized to Dpt; 10 with non-SIT treatment and 33 under SCIT, just before (SCIT-T0) and 4 h after administration (SCIT-T4). Moreover, IFNα mRNA expression was evaluated in purified pDCs, by qRT-PCR.

Results

After SCIT administration we observed a strong decrease of circulating pDCs, although accompanied by higher levels of IFNα mRNA expression, and an increase of circulating CD16⁺ monocytes. AR participants under SCIT exhibited a higher expression of receptor-bound IgE in all cell populations that expressed the high affinity receptor for IgE (FcεRI) and a higher frequency of CD16⁺ monocytes producing TNFα. Conversely, we observed a decrease in the frequency of mDCs producing TNFα in AR under SCIT, similar to the observed in the control group.

Conclusions

SCIT seems to induce numeric, phenotypic, and functional changes in circulating monocytes and dendritic cells, contributing at least in part to the well described immunological alterations induced by this type of immunotherapy.

The Biology of Monocytes and Dendritic Cells: Contribution to HIV Pathogenesis

Myeloid cells such as monocytes, dendritic cells (DC) and macrophages (MΦ) are key components of the innate immune system contributing to the maintenance of tissue homeostasis and the development/resolution of immune responses to pathogens. Monocytes and DC, circulating in the blood or infiltrating various lymphoid and non-lymphoid tissues, are derived from distinct bone marrow precursors and are typically short lived. Conversely, recent studies revealed that subsets of tissue resident MΦ are long-lived as they originate from embryonic/fetal precursors that have the ability to self-renew during the life of an individual. Pathogens such as the human immunodeficiency virus type 1 (HIV-1) highjack the functions of myeloid cells for viral replication (e.g., MΦ) or distal dissemination and cell-to-cell transmission (e.g., DC). Although the long-term persistence of HIV reservoirs in CD4+ T-cells during viral suppressive antiretroviral therapy (ART) is well documented, the ability of myeloid cells to harbor replication competent viral reservoirs is still a matter of debate. This review summarizes the current knowledge on the biology of monocytes and DC during homeostasis and in the context of HIV-1 infection and highlights the importance of future studies on long-lived resident MΦ to HIV persistence in ART-treated patients.

MicroRNA: Dynamic Regulators of Macrophage Polarization and Plasticity

The ability of a healthy immune system to clear the plethora of antigens it encounters incessantly relies on the enormous plasticity displayed by the comprising cell types. Macrophages (MΦs) are crucial member of the mononuclear phagocyte system (MPS) that constantly patrol the peripheral tissues and are actively recruited to the sites of injury and infection. In tissues, infiltrating monocytes replenish MΦ. Under the guidance of the local micro-milieu, MΦ can be activated to acquire specialized functional phenotypes. Similar to T cells, functional polarization of macrophage phenotype viz., inflammatory (M1) and reparative (M2) is proposed. Equipped with diverse toll-like receptors (TLRs), these cells of the innate arm of immunity recognize and phagocytize antigens and secrete cytokines that activate the adaptive arm of the immune system and perform key roles in wound repair. Dysregulation of MΦ plasticity has been associated with various diseases and infection. MicroRNAs (miRNAs) have emerged as critical regulators of transcriptome output. Their importance in maintaining health, and their contribution toward disease, encompasses virtually all aspects of human biology. Our understanding of miRNA-mediated regulation of MΦ plasticity and polarization can be utilized to modulate functional phenotypes to counter their role in the pathogenesis of numerous disease, including cancer, autoimmunity, periodontitis, etc. Here, we provide an overview of current knowledge regarding the role of miRNA in shaping MΦ polarization and plasticity through targeting of various pathways and genes. Identification of miRNA biomarkers of diagnostic/prognostic value and their therapeutic potential by delivery of miRNA mimics or inhibitors to dynamically alter gene expression profiles in vivo is highlighted.

The MHC class II antigen presentation pathway in human monocytes differs by subset and is regulated by cytokines

Monocytes play a critical role in the innate and adaptive immune systems, performing phagocytosis, presenting antigen, and producing cytokines. They are a heterogeneous population that has been divided in humans into classical, intermediate, and non-classical subsets, but the roles of these subsets are incompletely understood. In this study, we investigated the expression patterns of MHC class II (MHCII) and associated molecules and find that the intermediate monocytes express the highest levels of the MHC molecules, HLA-DR (tested in n = 30 samples), HLA-DP (n = 30), and HLA-DQ (n = 10). HLA-DM (n = 30), which catalyzes the peptide exchange on the MHC molecules, is also expressed at the highest levels in intermediate monocytes. To measure HLA-DM function, we measured levels of MHCII-bound CLIP (class II invariant chain peptide, n = 23), which is exchanged for other peptides by HLA-DM. We calculated CLIP:MHCII ratios to normalize CLIP levels to MHCII levels, and found that intermediate monocytes have the lowest CLIP:MHCII ratio. We isolated the different monocyte subsets (in a total of 7 samples) and analyzed their responses to selected cytokines as model of monocyte activation: two M1-polarizing cytokines (IFNγ, GM-CSF), an M2-polarizing cytokine (IL-4) and IL-10. Classical monocytes exhibit the largest increases in class II pathway expression in response to stimulatory cytokines (IFNγ, GM-CSF, IL-4). All three subsets decrease HLA-DR levels after IL-10 exposure. Our findings argue that intermediate monocytes are the most efficient constitutive antigen presenting subset, that classical monocytes are recruited into an antigen presentation role during inflammatory responses and that IL-10 negatively regulates this function across all subsets.

Phenotype, function, and differentiation potential of human monocyte subsets

Human monocytes have been grouped into classical (CD14++CD16-), non-classical (CD14dimCD16++), and intermediate (CD14++CD16+) subsets. Documentation of normal function and variation in this complement of subtypes, particularly their differentiation potential to dendritic cells (DC) or macrophages, remains incomplete. We therefore phenotyped monocytes from peripheral blood of healthy subjects and performed functional studies on high-speed sorted subsets. Subset frequencies were found to be tightly controlled over time and across individuals. Subsets were distinct in their secretion of TNFα, IL-6, and IL-1β in response to TLR agonists, with classical monocytes being the most producers and non-classical monocytes the least. Monocytes, particularly those of the non-classical subtype, secreted interferon-α (IFN-α) in response to intracellular TLR3 stimulation. After incubation with IL-4 and GM-CSF, classical monocytes acquired monocyte-derived DC (mo-DC) markers and morphology and stimulated allogeneic T cell proliferation in MLR; intermediate and non-classical monocytes did not. After incubation with IL-3 and Flt3 ligand, no subset differentiated to plasmacytoid DC. After incubation with GM-CSF (M1 induction) or macrophage colony-stimulating factor (M-CSF) (M2 induction), all subsets acquired macrophage morphology, secreted macrophage-associated cytokines, and displayed enhanced phagocytosis. From these studies we conclude that classical monocytes are the principal source of mo-DCs, but all subsets can differentiate to macrophages. We also found that monocytes, in particular the non-classical subset, represent an alternate source of type I IFN secretion in response to virus-associated TLR agonists.

Perturbations of Monocyte Subsets and Their Association with T Helper Cell Differentiation in Acute and Chronic HIV-1-Infected Patients

Monocytes have been recently subdivided into three subsets: classical (CD14++CD16−), intermediate (CD14++CD16+), and non-classical (CD14+CD16++) subsets, but phenotypic and functional abnormalities of the three monocyte subsets in HIV-1 infection have not been fully characterized, especially in acute HIV-1 infection (AHI). In the study, we explored the dynamic changes of monocyte subsets and their surface markers, and the association between monocyte subsets and the IFN-γ, interleukin (IL)-4, IL-17, and TNF-α producing CD4+ T cells in acute and chronic HIV-1-infected patients. We found that, in the acute HIV-1-infected individuals, the frequency of the intermediate CD14++CD16+ monocyte subsets, the CD163 density and HLA-DR density on intermediate CD14++CD16+ monocytes, and plasma soluble form of CD163 (sCD163) were significantly higher than that in healthy controls. Intermediate CD14++CD16+ monocyte subsets and their HLA-DR expression levels were inversely correlated with the CD4+ T cell counts, and the intermediate CD14++CD16+ monocytes were positively correlated with plasma sCD163. In contrast to the non-classical CD14+CD16++ and classical CD14++CD16− monocyte subsets, the frequency of the intermediate CD14++CD16+ monocytes was positively associated with the frequency of IFN-γ and IL-4 producing CD4+ T cells in HIV-1-infected patients. Taken together, our observations provide new insight into the roles of the monocyte subsets in HIV pathogenesis, particularly during AHI, and our findings may be helpful for the treatment of HIV-related immune activation.

Counts of bovine monocyte subsets prior to calving are predictive for postpartum occurrence of mastitis and metritis

The heightened susceptibility to infectious diseases in postpartum dairy cows is often attributed to immune dysfunction associated with the transition period. However, the cell populations involved in this immune dysfunction and the dynamics between those populations are not well defined. Monocytes play a crucial role in governing initial immune response in bacterial infections. Bovine monocytes are subdivided in classical (CD14⁺/CD16⁻), intermediate (CD14⁺/CD16⁺) and non-classical monocytes (CD14⁻/CD16⁺) with distinct phenotypic and functional differences. This study investigated the relationship of monocyte subsets counts in blood at 42 and 14 days prior to expected calving date to occurrence of metritis and mastitis within 2 weeks postpartum. In the enrolled prospective cohort of 27 German Holstein cows, housed at the Institute of Animal Nutrition of the Friedrich-Loeffler-Institute Braunschweig, Germany, n = 13 developed metritis and/or mastitis postpartum. A multivariable logistic regression was used to analyze the relationship between prepartum cell counts of monocyte subsets and neutrophils with postpartum disease. Our model revealed that higher counts of the two CD14⁺ monocyte subsets were predictive of disease. In contrast, higher numbers of the CD14⁻ monocyte subset were negatively associated with disease. Interestingly, the neutrophil count, a common hallmark for inflammatory response, was not associated with the outcome variable at either time point. The results indicate that the number and composition of monocyte subsets before calving are related to the susceptibility to infectious disease within 2 weeks postpartum. Furthermore the oppositional effect of CD14⁺ and CD14⁻ subsets strengthens the hypothesis that these subsets have different functional roles in the inflammatory response in dairy cows.

Basophil mediated pro-allergic inflammation in vehicle-emitted particles exposure

Despite of the fact that engine manufacturers develop a new technology to reduce exhaust emissions, insufficient attention given to particulate emissions. However, diesel exhaust particles are a major source of air-borne pollution, contain vast amount of polycyclic aromatic hydrocarbons (PAHs) and may have deleterious effects on the immune system, resulting in the induction and enhancement of pro-allergic processes. In the current study, vehicle emitted particles (VEP) from 2 different types of cars (diesel - D and gasoline - G) and locomotive (L) were collected. Overall, 129 four-week-old, male SPF-class Kunming mice were subcutaneously instilled with either low dose 100, 250 or high dose, 500mg/kg VEP and 15 mice were assigned as control group. The systemic toxicity was evaluated and alterations in the percentages of the CD3, CD4, CD8, CD16, CD25 expressing cells, basophils, eosinophils and neutrophils were determined. Basophil percentages were inversely associated with the PAH content of the VEPs, however basophil sensitization was more important than cell count in VEP exposure. Thus, the effects of VEP-PAHs emerge with the activation of basophils in an allergen independent fashion. Despite the increased percentage of CD4+ T cells, a sharp decrease in basophil counts at 500mg/kg of VEP indicates a decreased inhibitory effect of CD16+ monocytes on the proliferation of CD4+ T cell and suppressed polarization into a Th2 phenotype. Therefore, although the restrictions for vehicles emissions differ between countries, follow up studies and strict regulations are needed.

Infliximab Selectively Modulates the Circulating Blood Monocyte Repertoire in Crohn's Disease

BACKGROUND

Infliximab (IFX), an anti-tumour necrosis factor alpha (TNFα) monoclonal antibody, provides clinical benefits in treating Crohn's disease (CD) but its mechanisms of action are not fully elucidated. This study investigated blood monocyte repertoires and the acute effects of IFX infusion on monocyte subset phenotype and function in IFX-treated patients with CD.

METHODS

Monocytes and monocyte subsets were enumerated and phenotypically characterized by multicolor flow cytometry in freshly isolated blood from healthy controls (n = 21) and patients with CD treated with (IFX, n = 24) and without (non-IFX, n = 20) IFX. For the IFX-CD group, blood was sampled immediately before (tough-IFX) and after (peak-IFX) infusion. Monocyte responses to lipopolysaccharide were analyzed by whole-blood intracellular cytokine staining.

RESULTS

Non-IFX and IFX-CD patients had increased numbers of intermediate (CD14CD16) monocytes compared with healthy controls, whereas classical (CD14CD16) and nonclassical (CD14CD16) monocytes were numerically reduced in the IFX-CD group alone. In all groups, monocyte subsets expressed high surface levels of transmembrane (tm)TNFα. After IFX infusion, a significant reduction in monocyte numbers occurred. Post-IFX monocytopenia was proportionately greatest for classical and intermediate subsets, correlated with postinfusion IFX levels and was not associated with monocyte apoptosis. In contrast, lipopolysaccharide-induced production of TNFα and IL-12 by monocytes was significantly reduced in peak-IFX compared with trough-IFX blood samples.

CONCLUSIONS

Actively managed CD is associated with monocyte repertoire skewing suggestive of chronic inflammatory stimulation. Infused IFX acutely targets monocytes, likely by binding to tmTNFα, resulting in a non-apoptosis-related decline in circulating monocyte numbers and blunting of the inflammatory response of monocytes remaining in the blood.

slanDCs/M-DC8+ cells constitute a distinct subset of dendritic cells in human tonsils [corrected]

Human blood dendritic cells (DCs) include three main distinct subsets, namely the CD1c⁺ and CD141⁺ myeloid DCs (mDCs) and the CD303⁺ plasmacytoid DCs (pDCs). More recently, a population of slan/M-DC8⁺ cells, also known as “slanDCs”, has been described in blood and detected even in inflamed secondary lymphoid organs and non-lymphoid tissues. Nevertheless, hallmarks of slan/M-DC8⁺ cells in tissues are poorly defined. Herein, we report a detailed characterization of the phenotype and function of slan/M-DC8⁺ cells present in human tonsils. We found that tonsil slan/M-DC8⁺ cells represent a unique DC cell population, distinct from their circulating counterpart and also from all other tonsil DC and monocyte/macrophage subsets. Phenotypically, slan/M-DC8⁺ cells in tonsils display a CD11c⁺HLA-DR⁺CD14⁺CD11b^dim/negCD16^dim/negCX3CR1^dim/neg marker repertoire, while functionally they exhibit an efficient antigen presentation capacity and a constitutive secretion of TNFα. Notably, such DC phenotype and functions are substantially reproduced by culturing blood slan/M-DC8⁺ cells in tonsil-derived conditioned medium (TDCM), further supporting the hypothesis of a full DC-like differentiation program occurring within the tonsil microenvironment. Taken together, our data suggest that blood slan/M-DC8⁺ cells are immediate precursors of a previously unrecognizedcompetent DC subset in tonsils, and pave the way for further characterization of slan/M-DC8⁺ cells in other tissues.

Monocyte Heterogeneity: Consequences for Monocyte-Derived Immune Cells

Blood monocytes are precursors of dendritic cells, macrophages, and osteoclasts. They are a heterogeneous cell population with differences in size, phenotype, and function. Although monocytes maintain several tissue-specific populations of immune cells in homeostasis, their contribution to populations of dendritic cells, macrophages, and osteoclasts is significantly increased in inflammation. Identification of a growing number of functionally different subsets of cells within populations of monocyte-derived immune cells has recently put monocyte heterogeneity into sharp focus. Here, we summarize recent findings in monocyte heterogeneity and their differentiation into dendritic cells, macrophages, and osteoclasts. We also discuss these advances in the context of the formation of functionally different monocyte-derived subsets of dendritic cells, macrophages, and osteoclasts.

CD99 isoforms regulate CD1a expression in human monocyte-derived DCs through ATF-2/CREB-1 phosphorylation

CD1a expression is considered one of the major characteristics qualifying in vitro human dendritic cells (DCs) during their generation process. Here, we report that CD1A transcription is regulated by a mechanism involving the long and short isoforms of CD99. Using a lentiviral construct encoding for a CD99 short hairpin RNA, we were able to inhibit CD99 expression in human primary DCs. In such cells, CD1a membrane expression increased and CD1A transcripts were much higher in abundance compared to cells expressing CD99 long form (CD99LF). We also show that CD1A transcription is accompanied by a switch in expression from CD99LF to expression at comparable levels of both CD99 isoforms during immature DCs generation in vitro. We demonstrate that CD99LF maintains a lower level of CD1A transcription by up-regulating the phosphorylated form of the ATF-2 transcription factor and that CD99 short form (SF) is required to counteract this regulatory mechanism. Elucidation of the molecular mechanisms related to CD99 alternative splicing will be very helpful to better understand the transcriptional regulatory mechanism of CD1a molecules during DCs differentiation and its involvement in the immune response.

Atypical Activin A and IL-10 Production Impairs Human CD16+ Monocyte Differentiation into Anti-Inflammatory Macrophages

Human CD14(++)CD16(-) and CD14(+/lo)CD16(+) monocyte subsets comprise 85 and 15% of blood monocytes, respectively, and are thought to represent distinct stages in the monocyte differentiation pathway. However, the differentiation fates of both monocyte subsets along the macrophage (Mϕ) lineage have not yet been elucidated. We have now evaluated the potential of CD14(++) CD16(-) and CD16(+) monocytes to differentiate and to be primed toward pro- or anti-inflammatory Mϕs upon culture with GM-CSF or M-CSF, respectively (subsequently referred to as GM14, M14, GM16, or M16). Whereas GM16 and GM14 were phenotypic and functionally analogous, M16 displayed a more proinflammatory profile than did M14. Transcriptomic analyses evidenced that genes associated with M-CSF-driven Mϕ differentiation (including FOLR2, IL10, IGF1, and SERPINB2) are underrepresented in M16 with respect to M14. The preferential proinflammatory skewing of M16 relative to M14 was found to be mediated by the secretion of activin A and the low levels of IL-10 produced by M16. In fact, activin A receptor blockade during the M-CSF-driven differentiation of CD16(+) monocytes, or addition of IL-10-containing M14-conditioned medium, significantly enhanced their expression of anti-inflammatory-associated molecules while impairing their acquisition of proinflammatory-related markers. Thus, we propose that M-CSF drives CD14(++)CD16- monocyte differentiation into bona fide anti-inflammatory Mϕs in a self-autonomous manner, whereas M-CSF-treated CD16(+) monocytes generate Mϕs with a skewed proinflammatory profile by virtue of their high activin A expression unless additional anti-inflammatory stimuli such as IL-10 are provided.

Dendritic Cells Differentiated from Human Umbilical Cord Blood-Derived Monocytes Exhibit Tolerogenic Characteristics

Human umbilical cord blood (UCB) is rich in diverse hematopoietic stem cells that are competent to differentiate into various cell types with immunological compatibility at transplantation. Thus, UCB is a potential source for the preparation of dendritic cells (DCs) to be used for cell therapy against inflammatory disorders or cancers. However, the immunological properties of UCB-derived DCs are not fully characterized. In this study, we investigated the phenotypes and functions of UCB monocyte-derived DCs (UCB-DCs) in comparison with those of adult peripheral blood (APB) monocyte-derived DCs (APB-DCs). UCB-DCs contained less CD1a(+) DCs, which is known as immunostimulatory DCs, than APB-DCs. UCB-DCs exhibited lower expression of CD80, MHC proteins, and DC-SIGN, but higher endocytic activity, than APB-DCs. Lipopolysaccharide stimulation of UCB-DCs minimally augmented the expression of maturation markers and production of interleukin (IL)-12 and tumor necrosis factor (TNF)-α, but potently expressed IL-10. When UCB-DCs were cocultured with CD14(+) cell-depleted allogeneic peripheral blood mononuclear cells, they weakly induced the proliferation, surface expression of activation markers, and interferon (IFN)-γ production of T lymphocytes compared with APB-DCs. UCB possessed higher levels of prostaglandin E2 (PGE2) than APB, which might be responsible for tolerogenic phenotypes and functions of UCB-DCs. Indeed, APB-DCs prepared in the presence of PGE2 exhibited CD1a(-)CD14(+) phenotypes with tolerogenic properties, including weak maturation, impaired IL-12 production, and negligible T lymphocyte activation as UCB-DCs did. Taken together, we suggest that UCB-DCs have tolerogenic properties, which might be due to PGE2 highly sustained in UCB.

A single bout of dynamic exercise by healthy adults enhances the generation of monocyte-derived-dendritic cells

The ex vivo generation of monocyte-derived-dendritic cells (mo-DCs) has facilitated the use of DCs in immunotherapy research. However, low blood monocyte numbers frequently limit the manufacture of sufficient numbers of mo-DCs for subsequent experimental and clinical procedures. Because exercise mobilizes monocytes to the blood, we tested if acute dynamic exercise by healthy adults would augment the generation of mo-DCs without compromising their differentiation or function. We compared mo-DC generation from before- and after-exercise blood over 8-days of culture. Function was assessed by FITC-dextran uptake and the stimulation of autologous cytomegalovirus (pp65)-specific-T-cells. Supporting the hypothesis, we found a near fourfold increase in number of mo-DCs generated after-exercise. Furthermore, relative FITC-dextran uptake, differentiation rate, and stimulation of pp65-specific-T-cells did not differ between before- and after-exercise mo-DCs. We conclude that exercise enhances the ex vivo generation of mo-DCs without compromising their function, and so may overcome some limitations associated with manufacturing these cells for immunotherapy.

Differential expression of the fractalkine chemokine receptor (CX3CR1) in human monocytes during differentiation

Circulating monocytes (Mos) may continuously repopulate macrophage (MAC) or dendritic cell (DC) populations to maintain homeostasis. MACs and DCs are specialized cells that play different and complementary immunological functions. Accordingly, they present distinct migratory properties. Specifically, whereas MACs largely remain in tissues, DCs are capable of migrating from peripheral tissues to lymphoid organs. The aim of this work was to analyze the expression of the fractalkine receptor (CX3CR1) during the monocytic differentiation process. Freshly isolated Mos express high levels of both CX3CR1 mRNA and protein. During the Mo differentiation process, CX3CR1 is downregulated in both DCs and MACs. However, MACs showed significantly higher CX3CR1 expression levels than did DC. We also observed an antagonistic CX3CR1 regulation by interferon (IFN)-γ and interleukin (IL)-4 during MAC activation through the classical and alternative MAC pathways, respectively. IFN-γ inhibited the loss of CX3CR1, but IL-4 induced it. Additionally, we demonstrated an association between CX3CR1 expression and apoptosis prevention by soluble fractalkine (sCX3CL1) in Mos, DCs and MACs. This is the first report demonstrating sequential and differential CX3CR1 modulation during Mo differentiation. Most importantly, we demonstrated a functional link between CX3CR1 expression and cell survival in the presence of sCX3CL1.

Functional phenotype of synovial monocytes modulating inflammatory T-cell responses in rheumatoid arthritis (RA)

Monocytes function as crucial innate effectors in the pathogenesis of chronic inflammatory diseases, including autoimmunity, as well as in the inflammatory response against infectious pathogens. Human monocytes are heterogeneous and can be classified into three distinct subsets based on CD14 and CD16 expression. Although accumulating evidence suggests distinct functions of monocyte subsets in inflammatory conditions, their pathogenic roles in autoimmune diseases remain unclear. Thus, we investigated the phenotypic and functional characteristics of monocytes derived from synovial fluid and peripheral blood in RA patients in order to explore the pathogenic roles of these cells. In RA patients, CD14+CD16+, but not CD14dimCD16+, monocytes are predominantly expanded in synovial fluid and, to a lesser degree, in peripheral blood. Expression of co-signaling molecules of the B7 family, specifically CD80 and CD276, was markedly elevated on synovial monocytes, while peripheral monocytes of RA and healthy controls did not express these molecules without stimulation. To explore how synovial monocytes might gain these unique properties in the inflammatory milieu of the synovial fluid, peripheral monocytes were exposed to various stimuli. CD16 expression on CD14+ monocytes was clearly induced by TGF-β, although co-treatment with IL-1β, TNF-α, or IL-6 did not result in any additive effects. In contrast, TLR stimulation with LPS or zymosan significantly downregulated CD16 expression such that the CD14+CD16+ monocyte subset could not be identified. Furthermore, treatment of monocytes with IFN-γ resulted in the induction of CD80 and HLA-DR expression even in the presence of TGF-β. An in vitro assay clearly showed that synovial monocytes possess the unique capability to promote Th1 as well as Th17 responses of autologous peripheral CD4 memory T cells. Our findings suggest that the cytokine milieu of the synovial fluid shapes the unique features of synovial monocytes as well as their cardinal role in shaping inflammatory T-cell responses in RA.

TLR-2 and TLR-4 expression in monocytes of newborns with late-onset sepsis

OBJECTIVE

To analyze toll-like receptor (TLR)-2 and TLR-4 expression in monocytes of newborns with late-onset sepsis.

METHODS

This prospective study included 27 full-term newborns aged 8 to 29 days, with clinical and laboratory diagnosis of late-onset sepsis. Ten newborns (37%) had positive cultures. Cytokines were measured by cytometric bead array in peripheral blood, while TLR-2, TLR-4 expression, and median fluorescence intensity (MFI) were determined by immunophenotyping peripheral whole blood monocytes, and were analyzed with a BD FACSDiva flow cytometer (Becton, Dickinson and Company, USA). A comparison was performed with healthy adults.

RESULTS

Microorganisms were identified in 37% of these septic newborns, and all of them had high levels of pro-inflammatory cytokines (IL-8, IL-6, IL-1β) and anti-inflammatory cytokine (IL-10) corroborating the inflammatory/septic process. In monocytes, the frequency of TLR-4 expression was higher in infected newborns (p = 0.01).

CONCLUSION

This study investigated the innate immune response in septic newborns. Septic newborns that relied almost exclusively on the innate immune system showed little in vivo response at monocyte activation, suggesting impaired immune response and increased susceptibility to infection.

Alterations to the frequency and function of peripheral blood monocytes and associations with chronic disease in the advanced-age, frail elderly

Background

Circulating myeloid cells are important mediators of the inflammatory response, acting as a major source of resident tissue antigen presenting cells and serum cytokines. They represent a number of distinct subpopulations whose functional capacity and relative concentrations are known to change with age. Little is known of these changes in the very old and physically frail, a rapidly increasing proportion of the North American population.

Design

In the following study the frequency and receptor expression of blood monocytes and dendritic cells (DCs) were characterized in a sample of advanced-age, frail elderly (81–100 yrs), and compared against that of adults (19–59 yrs), and community-dwelling seniors (61–76 yrs). Cytokine responses following TLR stimulation were also investigated, as well as associations between immunophenotyping parameters and chronic diseases.

Results

The advanced-age, frail elderly had significantly fewer CD14(++) and CD14(+)CD16(+), but not CD14(++)CD16(+) monocytes, fewer plasmacytoid and myeloid DCs, and a lower frequency of monocytes expressing the chemokine receptors CCR2 and CX₃CR1. At baseline and following stimulation with TLR-2 and -4 agonists, monocytes from the advanced-age, frail elderly produced more TNF than adults, although the overall induction was significantly lower. Finally, monocyte subset frequency and CX₃CR1 expression was positively associated with dementia, while negatively associated with anemia and diabetes in the advanced-age, frail elderly.

Conclusions

These data demonstrate that blood monocyte frequency and phenotype are altered in the advanced-age, frail elderly and that these changes correlate with certain chronic diseases. Whether these changes contribute to or are caused by these conditions warrants further investigation.

Enhanced apoptosis of monocytes from complication-free juvenile-onset diabetes mellitus type 1 may be ameliorated by TNF-α inhibitors

Diabetes mellitus type 1 is associated with an enhanced apoptosis of different cells and tissues, accelerating occurrence of diabetic microvascular complications. The aim of our study was to determine spontaneous apoptotic potential of the monocyte subsets in juvenile-onset complication-free diabetes mellitus type 1 and to compare them with the corresponding values of the healthy. Moreover, we wanted to assess effects of TNF-R1 blocking agents and those of general TNF-α blocker (Infliximab) on spontaneous apoptosis of monocytes. Sixty randomly selected DM1 patients (14.5 ± 3.2 years) and 30 healthy (13.5 ± 2.8 years) volunteers were enrolled in the study. Our results indicate that three monocyte subsets are distinguishable in the groups of young diabetic patients and the healthy, similarly to in the blood of adults. DM1 patients were characterized by higher values of apoptotic monocytes than the healthy. The manipulation with drugs inhibiting TNF-R1 expression diminished the pool of CD16(+) apoptotic monocytes. Infliximab reduced the apoptotic CD16(-) cells. In conclusion, diabetes mellitus type 1 is associated with greater apoptosis of three monocyte subsets which may contribute to the development of microvascular complications. TNF-α modifiers appear to ameliorate monocyte apoptosis. They may be useful for controlling excessive monocyte apoptosis in diabetic patients.

Targeting monocyte and macrophage subpopulations for immunotherapy: a patent review (2009 - 2013)

INTRODUCTION

Monocytes and macrophages are heterogeneous populations of effector cells in the innate immune system. Once thought to be obligatory precursors for macrophages, monocytes are now known to have several distinct sub-populations and their own independent functions. This separation of the two lineages has opened new therapeutic avenues in inflammation and created new technologies targeting the mononuclear phagocyte system (MPS).

AREAS COVERED

A search of Google Patents and PatentScope has revealed numerous patents targeting monocytes and macrophages. This review will focus on seven patents from 2009 to 2013, utilizing autologous monocyte and macrophage adoptive transfer, genetic manipulation of the MPS, therapeutic nanoparticles and liposomes or combinations of these strategies. Patents that target monocyte recruitment are also briefly reviewed.

EXPERT OPINION

While monocyte and macrophage targeting has yielded some promising results in animal models, these often fail to translate well to successful clinical trials. The paradigm of how cells in the MPS interact and evolve is constantly being updated, and caution must be exercised in developing immunomodulatory agents until this relationship is better understood.

Transcriptomic network support distinct roles of classical and non-classical monocytes in human

Classical and non-classical monocytes are two well-defined subsets of monocytes displaying distinct roles. They differentially express numerous genes relevant to their primary role. Using five independent transcriptomic microarray datasets, we ruled out several inconsistent genes and identified common genes consistently overexpressed either in classical or non-classical monocytes. One hundred and eight genes were significantly increased in classical monocytes and are involved in bacterial defense, inflammation and atherosclerosis. Whereas the 74 genes overexpressed in non-classical monocytes are involved in cytoskeletal dynamics and invasive properties for enhanced motility and infiltration. These signatures unravel the biological functions of monocyte subsets. HIGHLIGHTS We compared five transcriptomic GEO datasets of human monocyte subsets. 108 genes in classical and 74 genes in non-classical monocytes are upregulated. Upregulated genes in classical monocytes support anti-bacterial and inflammatory responses. Upregulated genes in non-classical monocytes support patrolling and infiltration functions.

Statins enhance the effects of corticosteroids on the balance between regulatory T cells and Th17 cells

BACKGROUND

Plasticity of CD4(+) lymphocyte Th17/regulatory T cell (Treg) subsets is involved in the pathogenesis of chronic airway inflammatory diseases, such as asthma. Reversal of Th17/Treg cell balance towards Treg cells may be beneficial for the suppression of chronic Th2 cell-mediated inflammatory diseases, such as asthma. However, the effect of the combination of corticosteroids and a statin on the ratio of Treg/Th17 cells is unknown.

OBJECTIVE

We investigated the in vitro effects of the combination of simvastatin and fluticasone propionate (FP) on the numbers of Treg and Th17 cells in asthmatic patients after co-incubation with monocyte-derived DCs (mDCs), and explored the underlying signalling pathways involved.

METHODS

Using flow cytometry, we determined the effects of FP and simvastatin on Treg/Th17 balance after co-incubation of asthmatic CD4(+) T cells with mDCs. We also measured the relevant Treg and Th17-polarizing cytokines released from mDCs and also investigated the role of indoleamine 2, 3-dioxygenase (IDO) in this response.

RESULTS

The combination of simvastatin and FP significantly increased Treg and concomitantly reduced Th17 cell numbers to a greater extent than FP or statin treatment alone. The enhancing effects of simvastatin on FP effects were mediated through the up-regulation of indoleamine 2, 3-dioxygenase and interleukin (IL)-10, together with down-regulation of IL-6 and IL-23 expression in mDCs.

CONCLUSION

On the basis of this in vitro model of asthma, we suggest that the combination of a statin and a corticosteroid could augment the Treg/Th17 cell ratio and thus more effectively suppress airway inflammation in asthma patients. This may be particularly relevant in the treatment of severe asthma where Th17 cells are activated and linked to neutrophilic inflammation.

Impaired dendritic cell differentiation of CD16-positive monocytes in tuberculosis: role of p38 MAPK

Tuberculosis (TB) is one of the world's most pernicious diseases mainly due to immune evasion strategies displayed by its causative agent Mycobacterium tuberculosis (Mtb). Blood monocytes (Mos) represent an important source of DCs during chronic infections; consequently, the alteration of their differentiation constitutes an escape mechanism leading to mycobacterial persistence. We evaluated whether the CD16(+)/CD16(-) Mo ratio could be associated with the impaired Mo differentiation into DCs found in TB patients. The phenotype and ability to stimulate Mtb-specific memory clones DCs from isolated Mo subsets were assessed. We found that CD16(-) Mos differentiated into CD1a(+) DC-SIGN(high) cells achieving an efficient recall response, while CD16(+) Mos differentiated into a CD1a(-) DC-SIGN(low) population characterized by a poor mycobacterial Ag-presenting capacity. The high and sustained phosphorylated p38 expression observed in CD16(+) Mos was involved in the altered DC profile given that its blockage restored DC phenotype and its activation impaired CD16(-) Mo differentiation. Furthermore, depletion of CD16(+) Mos indeed improved the differentiation of Mos from TB patients toward CD1a(+) DC-SIGN(high) DCs. Therefore, Mos from TB patients are less prone to differentiate into DCs due to their increased proportion of CD16(+) Mos, suggesting that during Mtb infection Mo subsets may have different fates after entering the lungs.

CD16+ monocytes control T-cell subset development in immune thrombocytopenia

Immune thrombocytopenia (ITP) results from decreased platelet production and accelerated platelet destruction. Impaired CD4(+) regulatory T-cell (Treg) compartment and skewed Th1 and possibly Th17 responses have been described in ITP patients. The trigger for aberrant T-cell polarization remains unknown. Because monocytes have a critical role in development and polarization of T-cell subsets, we explored the contribution of monocyte subsets in control of Treg and Th development in patients with ITP. Unlike circulating classic CD14(hi)CD16(-) subpopulation, the CD16(+) monocyte subset was expanded in ITP patients with low platelet counts on thrombopoietic agents and positively correlated with T-cell CD4(+)IFN-γ(+) levels, but negatively with circulating CD4(+)CD25(hi)Foxp3(+) and IL-17(+) Th cells. Using a coculture model, we found that CD16(+) ITP monocytes promoted the expansion of IFN-γ(+)CD4(+) cells and concomitantly inhibited the proliferation of Tregs and IL-17(+) Th cells. Th-1-polarizing cytokine IL-12, secreted after direct contact of patient T-cell and CD16(+) monocytes, was responsible for the inhibitory effect on Treg and IL-17(+)CD4(+) cell proliferation. Our findings are consistent with ITP CD16(+) monocytes promoting Th1 development, which in turn negatively regulates IL-17 and Treg induction. This underscores the critical role of CD16(+) monocytes in the generation of potentially pathogenic Th responses in ITP.

Expression of a versatile DC-targeting fusion protein using an Adenovirus expression system

The importance of viral and tumour vaccines in eliciting elicit strong CD8+ T-cell responses has been widely acknowledged. Strategies exploring ways to enhance CD8+ T-cell responses have been developed, including targeting of vaccine antigens to dendritic cell (DC) receptors to access to the cross presentation pathway. Many DC endocytic receptors could potentially lead to augmented CD8+ T-cell responses if antigens were targeted directly to them, however only a few receptors have been explored because current targeting reagents are limited in the number of receptors that they are able to target. Consequently, this study describes the production and purification of a streptavidin-fusion protein that provides a versatile and efficient means to target antigen to more than one DC receptor. A model antigen gene, CMV pp65, and a streptavidin core gene, were spliced together using an overlap-extension PCR technique. The resulting fusion gene was cloned into a vector allowing expression in an Adenovirus-based expression system. Expression was verified and optimised before Ni-NTA affinity chromatography purification. Evaluation of pp65-streptavidin immunogenicity revealed that it elicits similar levels of CD8+ T-cell proliferative responses as pp65 and is able to effectively target specific DC receptors when used in addition to biotinylated receptor-specific antibodies. Additionally, enhancement of CD8+ T-cell responses was shown after directing pp65-strep to selected DC receptors in preliminary in vitro experiments. Collectively, this highlights the ease of production of a streptavidin-fusion protein, and demonstrates its use as a promising strategy to evaluate numerous DC receptors as potential targets in vaccine strategies.

Case reports of sarcoma patients with optimized lectin-oriented mistletoe extract therapy

BACKGROUND

Mistletoe (Viscum album L) extracts (ME) are widespread as immunomodulatory therapeutic agents in alternative tumor treatment. Assessing the often-controversial clinical results is rather difficult since the effects of ME on the immune system cannot be equally reproduced. Mistletoe lectins (ML) are the only mistletoe ingredients also found in vivo that are capable of having a positive effect on the immune balance of patients with tumors. Other components have only been tested in vitro, and the removal of mistletoe lectins ML from the extract can put an end to the immunological efficacy of ME. Preclinical investigations in the tumor models (using nude mice xenotransplanted with human leiomyosarcoma and interleukin-12-deficient C57BL6 mice) show that without immunological reactions, ME induce less antitumor efficacy. ML, functioning as ligands for pattern recognition receptors of the natural immune system, are docked to ganglioside molecules (CD75) of monocytes and granulocytes, thereby stimulating the natural antitumor mechanisms.

OBJECTIVES

The aim of this article is to present and discuss several favorable clinical responses of patients who had sarcoma and who were treated with immunologically effective ME preparations. COURSE OF THERAPY AND RESULTS: In accordance with the bell-shaped dose-response relationship of ML, the patients with sarcoma were treated with ME preparations, standardized for the active sugar-binding lectin contents. Thus, an optimal dose of 0.75-1.0 ng/kg ML was given twice a week subcutaneously. In this report, the clinical progress of 6 patients with sarcoma showed remissions of tumor symptoms.

CONCLUSIONS

It seems that this disease is beneficially influenced by optimized lectin-oriented ME therapy since patients with sarcoma may react especially well to the improved balance of natural immunological mechanisms. These case reports require further clinical studies with patients with sarcoma.

Expansion of CD14+CD16+ monocytes producing TNF-α in complication-free diabetes type 1 juvenile onset patients

We concentrated on the complication-free phase of juvenile onset type 1 diabetes mellitus (T1DM) searching for associations between concentration of inflammatory factors TNF-α, CRP and VEGF and two monocyte subsets the CD14(++)CD16(-) and CD14(+)CD16(+). We analysed a randomly selected group of 150 patients without complications (disease duration 2.74 ± 2.51 years) at the start of the project and 5 years later. They were compared with 24 patients with retinopathy (6.53 ± 3.39 years of disease) and 30 healthy volunteers. Our results indicate that in the complication-free period the concentration of TNF-α significantly increased and continued to increase after retinopathy was established. After 5 years the percentage and absolute number of CD14(+)CD16(+) monocytes doubled in complication-free patients. Our study indicates that the size of CD14(+)CD16(+) monocyte subset may be used alternatively to CRP values as an indicator of inflammation grade. Our results imply the necessity of trials using anti-TNF-α therapy in the complication-free phase of the disease.