Differential capacity of human interleukin-4 and interferon-α monocyte-derived dendritic cells for cross-presentation of free versus cell-associated antigen

Human dendritic cell subsets in the glioblastoma-associated microenvironment

Glioblastoma (GBM) is the most aggressive type of glioma (Grade IV). The presence of cytotoxic T lymphocyte (CTLs) has been associated with improved outcomes in patients with GBM, and it is believed that the activation of CTLs by dendritic cells may play a critical role in controlling the growth of GBM. DCs are professional antigen-presenting cells (APC) that orchestrate innate and adaptive anti-GBM immunity. DCs can subsequently differentiate into plasmacytoid DCs (pDC), conventional DC1 (cDC1), conventional (cDC2), and monocyte-derived DCs (moDC) depending on environmental exposure. The different subsets of DCs exhibit varying functional capabilities in antigen presentation and T cell activation in producing an antitumor response. In this review, we focus on recent studies describing the phenotypic and functional characteristics of DC subsets in humans and their respective antitumor immunity and immunotolerance roles in the GBM-associated microenvironment. The critical components of crosstalk between DC subsets that contribute significantly to GBM-specific immune responses are also highlighted in this review with reference to the latest literature. Since DCs could be prime targets for therapeutic intervention, it is worth summarizing the relevance of DC subsets with respect to GBM-associated immunologic tolerance and their therapeutic potential.

The synergistic and enhancive effects of IL-6 and M-CSF to expand and differentiate functional dendritic cells from human monocytes under serum-free condition

BACKGROUND

Dendritic cells (DCs) are differentiated from monocytes, and have a strong ability to perform phagocytosis, present antigens and activate T cell immune response. Therefore, DCs are one of the key factors in fighting cancer in immunotherapy, and it is an important issue to develop a serum-free system for DC differentiation and expansion in vitro for clinical application.

RESULTS

In this study, IL-6 and M-CSF were determined and a concentration combination of cytokines was optimized to develop an optimal DC serum-free differentiation medium (SF-DC Optimal) that can effectively differentiate CD14⁺ monocytes into CD40⁺CD209⁺ DCs. After differentiation, the morphology, growth kinetics, surface antigen expression, phagocytosis ability, cytokine secretion, mixed lymphocyte reaction and stimulation for maturation of the differentiated DCs were checked and confirmed. Importantly, this research is the first report finding that the addition an extra low concentration of IL-6 and M-CSF exhibited a synergistic effect with GM-CSF and IL-4 to generate higher numbers and more fully functional DCs than the addition of GM-CSF and IL-4 only under serum-free condition.

CONCLUSION

A large number of functional DCs can be generated by using SF-DC Optimal medium and provide an alternative source of DCs for related basic research and clinical applications.

Emerging Strategies of Engineering and Tracking Dendritic Cells for Cancer Immunotherapy

Dendritic cells (DCs), a kind of specialized immune cells, play key roles in antitumor immune response and promotion of innate and adaptive immune responses. Recently, many strategies have been developed to utilize DCs in cancer therapy, such as delivering antigens and adjuvants to DCs and using scaffold to recruit and activate DCs. Here we outline how different DC subsets influence antitumor immunity, summarize the FDA-approved vaccines and cancer vaccines under clinical trials, discuss the strategies for engineering DCs and noninvasive tracking of DCs to improve antitumor immunotherapy, and reveal the potential of artificial neural networks for the design of DC based vaccines.

T cell infiltration on local CpG-B delivery in early-stage melanoma is predominantly related to CLEC9A+CD141+ cDC1 and CD14+ antigen-presenting cell recruitment

Background

We previously reported CpG-B injection at the primary tumor excision site prior to re-excision and sentinel node biopsy to result in immune activation of the sentinel lymph node (SLN), increased melanoma-specific CD8⁺ T cell rates in peripheral blood, and prolonged recurrence-free survival. Here, we assessed recruitment and activation of antigen-presenting cell (APC) subsets in the SLN and at the injection site in relation to T cell infiltration.

Methods

Re-excision skin specimens from patients with clinical stage I-II melanoma, collected 7 days after intradermal injection of either saline (n=10) or 8 mg CpG-B (CPG7909, n=12), were examined by immunohistochemistry, quantifying immune subsets in the epidermis, papillary, and reticular dermis. Counts were related to flow cytometric data from matched SLN samples. Additional in vitro cultures and transcriptional analyses on peripheral blood mononuclear cells (PBMCs) were performed to ascertain CpG-induced APC activation and chemokine profiles.

Results

Significant increases in CD83⁺, CD14⁺, CD68⁺, and CD123⁺ APC were observed in the reticular dermis of CpG-B-injected skin samples. Fluorescent double/triple staining revealed recruitment of both CD123⁺BDCA2⁺ plasmacytoid dendritic cells (DCs) and BDCA3/CD141⁺CLEC9A⁺ type-1 conventional DC (cDC1), of which only the cDC1 showed considerable levels of CD83 expression. Simultaneous CpG-B-induced increases in T cell infiltration were strongly correlated with both cDC1 and CD14 counts. Moreover, cDC1 and CD14⁺ APC rates in the reticular dermis and matched SLN suspensions were positively correlated. Flow cytometric, transcriptional, and chemokine release analyses of PBMC, on in vitro or in vivo exposure to CpG-B, indicate a role for the activation and recruitment of both cDC1 and CD14⁺ monocyte-derived APCs in the release of CXCL10 and subsequent T cell infiltration.

Conclusion

The CpG-B-induced concerted recruitment of cDC1 and CD14⁺ APC to the injection site and its draining lymph nodes may allow for both the (cross-)priming of T cells and their subsequent homing to effector sites.

Large-scale production and directed induction of functional dendritic cells ex vivo from serum-free expanded human hematopoietic stem cells

BACKGROUND

Dendritic cells (DCs) that are derived from hematopoietic stem cells (HSCs) are the most potent antigen-presenting cells and play a pivotal role in initiating the immune response. Hence, large-scale production and direct induction of functional DCs ex vivo from HSCs are crucial to HSC research and clinical potential, such as vaccines for cancer and immune therapy.

METHODS

In a previous study, we developed a serum-free HSC expansion system (SF-HSC medium) to expand large numbers of primitive HSCs ex vivo. Herein, a DC induction and expansion medium (DC medium) was proposed to further generate large numbers of functional DCs from serum-free expanded HSCs, which were developed and optimized by factorial design and the steepest ascent method.

RESULTS

The DC medium is composed of effective basal medium (Iscove's modified Dulbecco's medium [IMDM]) and cytokines (2.9 ng/mL stem cell factor [SCF], 2.1 ng/mL Flt-3 ligand, 3.6 ng/mL interleukin [IL]-1β, 19.3 ng/mL granulocyte-macrophage colony-stimulating factor [GM-CSF] and 20.0 ng/mL tumor necrosis factor-α [TNF-α]). After 10-day culture in DC medium, the maximum fold expansion for accumulated CD1a⁺CD11c⁺ DCs was more than 4000-fold, and the induced DCs were characterized and confirmed by analysis of growth kinetics, surface antigen expression, endocytosis ability, mixed lymphocyte reaction, specific cytokine secretion and lipopolysaccharide stimulation.

DISCUSSION

In conclusion, the combination of DC medium and SF-HSC medium can efficiently induce and expand a large amount of functional DCs from a small scale of HSCs and might be a promising source of DCs for vaccine and immune therapy in the near future.

The effect of age on foal monocyte-derived dendritic cell (MoDC) maturation and function after exposure to killed bacteria

Neonatal foals are uniquely susceptible to certain infections early in life. Dendritic cells (DC) are vital in the transition between the innate and adaptive immune response to infection, but DC biology in foals is not fully characterized. Monocyte-derived DC represent a suitable in vitro model similar to DC that differentiate from monocytes recruited from circulation. We hypothesized that foal monocyte-derived DC (MoDC) would exhibit age-dependent phenotypic and functional differences compared to adult horse MoDC. MoDC generated from 9 horses (collected once) and from 8 foals (collected at 1, 7, and 30 days-of-age) were exposed to killed whole cell Escherichia coli or Staphylococcus aureus bacteria. MoDC expression of MHC class II (MHC class-II), CD86, and CD14 were measured by flow cytometry, and supernatant cytokine concentrations of IL-4, IL-17, IFN-γ, and IL-10 were quantified with a validated immunoassay. The percentage of MoDC expressing MHC class-II and CD86 was lower and CD14 was higher for cells generated from 1-day-old foals compared to cells generated from adult horses (P < 0.0001). Bacterial exposure increased the percentage of cells expressing CD86 at all ages (P < 0.0001). Bacteria-exposed MoDC from 1-day-old foals produced significantly less IL-4, IL-17, and IFN-γ than adult MoDC produced in response to bacterial exposure (P ≤ 0.04). Following bacterial exposure, foal MoDC phenotype and cytokine secretion were different than those of mature horses. These differences could reduce the ability of foals to generate a protective immune response against bacterial infection.

Modulation of Immune Tolerance via Siglec-Sialic Acid Interactions

One of the key features of the immune system is its extraordinary capacity to discriminate between self and non-self and to respond accordingly. Several molecular interactions allow the induction of acquired immune responses when a foreign antigen is recognized, while others regulate the resolution of inflammation, or the induction of tolerance to self-antigens. Post-translational signatures, such as glycans that are part of proteins (glycoproteins) and lipids (glycolipids) of host cells or pathogens, are increasingly appreciated as key molecules in regulating immunity vs. tolerance. Glycans are sensed by glycan binding receptors expressed on immune cells, such as C-type lectin receptors (CLRs) and Sialic acid binding immunoglobulin type lectins (Siglecs), that respond to specific glycan signatures by triggering tolerogenic or immunogenic signaling pathways. Glycan signatures present on healthy tissue, inflamed and malignant tissue or pathogens provide signals for “self” or “non-self” recognition. In this review we will focus on sialic acids that serve as “self” molecular pattern ligands for Siglecs. We will emphasize on the function of Siglec-expressing mononuclear phagocytes as sensors for sialic acids in tissue homeostasis and describe how the sialic acid-Siglec axis is exploited by tumors and pathogens for the induction of immune tolerance. Furthermore, we highlight how the sialic acid-Siglec axis can be utilized for clinical applications to induce or inhibit immune tolerance.

Clearance of HBeAg and HBsAg of HBV in mice model by a recombinant HBV vaccine combined with GM-CSF and IFN-α as an effective therapeutic vaccine adjuvant

Chronic hepatitis B virus (CHB) infection is a significant public threat. Current interferon-α (IFN-α) based therapies and anti-viral drugs have failed to clear the infection in the majority of CHB patients and animal models. In our previous study, we established a combined protocol that employed a 3-day pretreatment with granulocyte-macrophage colony stimulating factor (GM-CSF) prior to a standard HBV vaccine. It achieved a 90% reduction of HBsAg level in the HBsAg transgenic mouse model. This protocol, while effective, remains too complex for clinical use. In this study, we formulated a new regimen by combining GM-CSF, IFN-α and a recombinant HBV vaccine (GM-CSF/IFN-α/VACCINE) into a single preparation and tested its efficacy in a HBV infection model. After four vaccinations, both serum HBeAg and HBsAg were cleared, accompanied by a 95% reduction of HBV⁺ hepatocytes and the presence of a large number of infiltrating CD8⁺ T cells in the liver. Mechanistically these robust responses were initiated by a vaccine-induced conversion of CCR2-dependent CD11b⁺Ly6C^hi monocytes into CD11b⁺CD11c⁺ DCs. This finding sheds light on the potential mechanism of action of the GM-CSF-based vaccine adjuvant and provides definable markers for clinical assessment during future testing of such highly potent vaccine protocols in HBV patients.

Use of antigen-primed dendritic cells for inducing antitumor immune responses in vitro in patients with non-small cell lung cancer

Cancer is associated with a reduction in immature and mature circulating dendritic cells (DCs), and with an impaired migratory capacity, compared with healthy donors. Therefore, modern approaches to the in vitro generation of DCs loaded with tumor antigens and their use for inducing antitumor immune responses in vivo are being investigated. The purpose of the present study was to investigate the phenotypic and functional characteristics of peripheral blood DC subsets in patients with non-small cell lung cancer (NSCLC), and the development of an antitumor cytotoxic response by mononuclear cells (MNCs) from patients using in vitro generated antigen-primed DCs. Heparinized peripheral venous blood samples were obtained from 10 healthy donors and 20 patients with a histologically verified diagnosis of NSCLC. The ability of antigen-activated DCs to stimulate the activity of MNCs against autologous tumor cells was evaluated using a cytotoxic test. Peripheral blood DC subsets from patients with NSCLC were identified to be decreased and to exhibit an impaired ability to mature, compared with healthy donors. Furthermore, DCs generated from MNCs from patients with NSCLC were able to stimulate a specific cytotoxic response when loaded with autologous tumor lysates or RNA and matured, in vitro. A perforin and granzyme B-dependent mode of cytotoxicity was primarily induced. The ability of DCs loaded with tumor antigens to increase the cytotoxic activity of MNCs against NSCLC cells in vitro indicates the effective induction and co-stimulation of T lymphocytes by the generated DCs.

A Human Cell Line Model for Interferon-α Driven Dendritic Cell Differentiation

The CD34⁺ MUTZ-3 acute myeloid leukemia cell line has been used as a dendritic cell (DC) differentiation model. This cell line can be cultured into Langerhans cell (LC) or interstitial DC-like cells using the same cytokine cocktails used for the differentiation of their primary counterparts. Currently, there is an increasing interest in the study and clinical application of DC generated in the presence of IFNα, as these IFNα-DC produce high levels of inflammatory cytokines and have been suggested to be more potent in their ability to cross-present protein antigens, as compared to the more commonly used IL-4-DC. Here, we report on the generation of IFNα-induced MUTZ-DC. We show that IFNα MUTZ-DC morphologically and phenotypically display characteristic DC features and are functionally equivalent to “classic” IL-4 MUTZ-DC. IFNα MUTZ-DC ingest exogenous antigens and can subsequently cross-present HLA class-I restricted epitopes to specific CD8⁺ T cells. Importantly, mature IFNα MUTZ-DC express CCR7, migrate in response to CCL21, and are capable of priming naïve antigen-specific CD8⁺ T cells. In conclusion, we show that the MUTZ-3 cell line offers a viable and sustainable model system to study IFNα driven DC development and functionality.