An alternative flow cytometry strategy for peripheral blood dendritic cell enumeration in the setting of repetitive GM-CSF dosing

Circadian misalignment impairs oligodendrocyte myelination via Bmal1 overexpression leading to anxiety and depression-like behaviors

Circadian misalignment (CM) caused by shift work can increase the risk of mood impairment. However, the pathological mechanisms underlying these deficits remain unclear. In the present study, we used long-term variable photoperiod (L-VP) in wild-type mice to better simulate real-life shift patterns and study its effects on the prefrontal cortex (PFC) and hippocampus, which are closely related to mood function. The results showed that exposure to L-VP altered the activity/rest rhythms of mice, by eliciting phase delay and decreased amplitude of the rhythms. Mice with CM developed anxiety and depression-like manifestations and the number of mature oligodendrocytes (OL) was reduced in the medial prefrontal cortex and hippocampal CA1 regions. Mood impairment and OL reduction worsened with increased exposure time to L-VP, while normal photoperiod restoration had no effect. Mechanistically, we identified upregulation of Bmal1 in the PFC and hippocampal regions of CM mice at night, when genes related to mature OL and myelination should be highly expressed. CM mice exhibited significant inhibition of the protein kinase B (AKT)/mTOR signaling pathway, which is directly associated to OL differentiation and maturation. Furthermore, we demonstrated in the OL precursor cell line Oli-Neu that overexpression of Bmal1 inhibits AKT/mTOR pathway and reduces the expression of genes OL differentiation. In conclusion, BMAL1 might play a critical role in CM, providing strong research evidence for BMAL1 as a potential target for CM therapy.

Phenotypic characterization of equine monocyte-derived dendritic cells generated ex vivo utilizing commercially available serum-free medium

The impact of culture conditions on equine monocyte-derived dendritic cells (MoDC) generation has not been fully characterized. We hypothesized that 1) MoDC could be cultured in a commercially available serum-free medium (AIM-V); and 2) that differential culture conditions would influence MoDC viability, yield and phenotype. MoDC generated from adult horses were cultured under variable conditions in a series of experiments. Viability was assessed using trypan blue and propidium iodide staining. Yield was determined by manual hemocytometer counting. Phenotype was assessed by flow cytometric analysis of surface markers (MHC class-II, CD86 and CD14). Data were analyzed using paired t-tests and repeated measures ANOVA. Two MoDC populations that differed in size and phenotype were identified: larger MoDC (LgMoDC) and smaller MoDC (SmMoDC). Medium type, plate chemistry, or length of monocyte adhesion time did not impact MoDC viability or yield. LgMoDC generated in serum-free medium expressed more MHC class-II and CD86 (P ≤ 0.03). A prolonged duration in culture reduced MoDC yield (P ≤ 0.04). MoDC can be consistently and reliably generated using AIM-V serum-free medium in standard tissue culture plates with a recommended culture duration of 3-4 days.

Dendritic cells: microbial clearance via autophagy and potential immunobiological consequences for periodontal disease

Dendritic cells are potent antigen‐capture and antigen‐presenting cells that play a key role in the initiation and regulation of the adaptive immune response. This process of immune homeostasis, as maintained by dendritic cells, is susceptible to dysregulation by certain pathogens during chronic infections. Such dysregulation may lead to disease perpetuation with potentially severe systemic consequences. Here we discuss in detail how intracellular pathogens exploit dendritic cells and escape degradation by altering or evading autophagy. This novel mechanism explains, in part, the chronic, persistent nature observed in several immuno‐inflammatory diseases, including periodontal disease. We also propose a hypothetical model of the plausible role of autophagy in the context of periodontal disease. Promotion of autophagy may open new therapeutic strategies in the search of a ‘cure’ for periodontal disease in humans.

Tumor-associated macrophages contribute to tumor progression in ovarian cancer

Ovarian cancer is the leading cause of death in women with gynecological malignancy and improvements in current treatments are needed. As with many other solid cancers, the ovarian tumor microenvironment is emerging as a key player in tumor progression and a potential therapeutic target. The tumor microenvironment contains several non-malignant cell types that are known to contribute to tumor progression and metastasis. Included in this population of non-malignant cells are several different types of immune cells, of which tumor-associated macrophages (TAMs) are the most abundant. An increasing amount of evidence is emerging to suggest that TAMs display a unique activation profile in ovarian tumors and are able to create an immunosuppressive microenvironment, allowing tumors to evade immune detection and promoting tumor progression. Therefore, an increased understanding of how these immune cells interact with tumor cells and the microenvironment will greatly benefit the development of more effective immunotherapies to treat ovarian cancer. This review focuses on the role of TAMs in the ovarian tumor microenvironment and how they promote tumor progression.

CD34-derived dendritic cells transfected ex vivo with HIV-Gag mRNA induce polyfunctional T-cell responses in nonhuman primates

The pivotal role of DCs in initiating immune responses led to their use as vaccine vectors. However, the relationship between DC subsets involved in antigen presentation and the type of elicited immune responses underlined the need for the characterization of the DCs generated in vitro. The phenotypes of tissue-derived APCs from a cynomolgus macaque model for human vaccine development were compared with ex vivo-derived DCs. Monocyte/macrophages predominated in bone marrow (BM) and blood. Myeloid DCs (mDCs) were present in all tested tissues and were more highly represented than plasmacytoid DCs (pDCs). As in human skin, Langerhans cells (LCs) resided exclusively in the macaque epidermis, expressing CD11c, high levels of CD1a and langerin (CD207). Most DC subsets were endowed with tissue-specific combinations of PRRs. DCs generated from CD34(+) BM cells (CD34-DCs) were heterogeneous in phenotype. CD34-DCs shared properties (differentiation and PRR) of dermal and epidermal DCs. After injection into macaques, CD34-DCs expressing HIV-Gag induced Gag-specific CD4(+) and CD8(+) T cells producing IFN-γ, TNF-α, MIP-1β, or IL-2. In high responding animals, the numbers of polyfunctional CD8(+) T cells increased with the number of booster injections. This DC-based vaccine strategy elicited immune responses relevant to the DC subsets generated in vitro.

A STATus report on DC development

DCs have a vital role in the immune system by recognizing exogenous or self-antigens and eliciting appropriate stimulatory or tolerogenic adaptive immune responses. DCs also contribute to human autoimmune disease and, when depleted, to immunodeficiency. Moreover, DCs are being explored for potential use in clinical therapies including cancer treatment. Thus, understanding the molecular mechanisms that regulate DCs is crucial to improving treatments for human immune disease and cancer. DCs constitute a heterogeneous population including plasmacytoid (pDC) and classic (cDC) subsets; however, the majority of DCs residing in lymphoid organs and peripheral tissues in steady state share common progenitor populations, originating with hematopoietic stem cells. Like other hematopoietic lineages, DCs require extracellular factors including cytokines, as well as intrinsic transcription factors, to control lineage specification, commitment, and maturation. Here, we review recent findings on the roles for cytokines and cytokine-activated STAT transcription factors in DC subset development. We also discuss how cytokines and STATs intersect with lineage-regulatory transcription factors and how insight into the molecular basis of human disease has revealed transcriptional regulators of DCs. Whereas this is an emerging area with much work remaining, we anticipate that knowledge gained by delineating cytokine and transcription factor mechanisms will enable a better understanding of DC subset diversity, and the potential to manipulate these important immune cells for human benefit.

Optimization of a whole blood intracellular cytokine assay for measuring innate cell responses to mycobacteria

Innate cells are essential for host defense against invading pathogens, and the induction and direction of adaptive immune responses to infection. We developed and optimized a flow cytometric assay that allows measurement of intracellular cytokine expression by monocytes, dendritic cells (DC) and granulocytes, as well as cellular uptake of green-fluorescent protein (GFP)-expressing mycobacteria, in very small volumes of peripheral blood. We show that innate cell stimulation resulted in increased granularity of monocytes and mDC and decreased granulocyte granularity that precluded flow cytometric discernment of granulocytes from monocytes and myeloid DC by forward and side scatter gating. Anti-CD66a/c/e antibody staining allowed reliable identification and exclusion of granulocytes for subsequent delineation of monocytes and myeloid DC. Intracellular cytokine expression by granulocytes, monocytes and mDC was remarkably sensitive to the dose of mycobacterial inoculum. Moreover, activation of monocytes and mDC with live BCG reduced expression levels of CD14 and CD11c, respectively, necessitating optimization of staining conditions to reliably measure these lineage markers. Finally, we characterized expression of IL-12/23p40, TNF-α, IL-6, and IL-10, by GFP(+) and GFP(-) monocytes and mDC from 25 healthy adults. This assay may be applied to the study of innate cell responses to any GFP-expressing pathogen, and can be performed on blood volumes as low as 200 μL per condition, making the assay particularly suitable for pediatric studies.

Restricted and selective tropism of a Venezuelan equine encephalitis virus-derived replicon vector for human dendritic cells

Dendritic cells (DCs) consist of heterogeneous phenotypic populations and have diverse immunostimulatory functions dependent on both lineage and functional phenotype, but as exceptionally potent antigen-presenting cells, they are targets for generating effective antigen-specific immune responses. A promising replicon particle vector derived from Venezuelan equine encephalitis virus (VEE) has been reported to transduce murine footpad DCs. However, the receptive DC subset, the degree of restriction for this tropism, and the extent of conservation between rodents and humans have not been well characterized. Using fresh peripheral blood DCs, mononuclear cells, monocyte-derived macrophages, and monocyte-derived DCs, our results demonstrate conservation of VEE replicon particle (VRP) tropism for DCs between humans and rodents. We observed that a subset of immature myeloid DCs is the target population, and that VRP-transduced immature DCs retain intact functional capacity, for example, the ability to resist the cytopathic effects of VRP transduction and the capacity to acquire the mature phenotype. These studies support the demonstration of selective VRP tropism for human DCs and provide further insight into the biology of the VRP vector, its parent virus, and human DCs.