Reciprocal control of T helper cell and dendritic cell differentiation

Design and Evaluation of ω-Hydroxy Fatty Acids Containing α-GalCer Analogues for CD1d-Mediated NKT Cell Activation

CD1d molecules recognize glycolipid antigens with straight chain fatty acid moieties. Although most of the residues in the CD1d binding groove are hydrophobic, some of the amino acids can form hydrogen bonds. Consequently, we have designed ω-hydroxy fatty acid-containing glycolipid derivatives of the prototypical CD1d ligand α-GalCer. The potency of the ω-hydroxy analogues of the proper length is comparable to that of α-GalCer. We propose, based on the biological results and molecular modeling studies, that a hydrogen bonding interaction is involved between the ω-hydroxy group and a polar amino acid residue in the hydrophobic binding groove.

Current vaccine trials in glioblastoma: a review

Glioblastoma (GBM) is the most common primary brain tumor, and despite aggressive therapy with surgery, radiation, and chemotherapy, average survival remains at about 1.5 years. The highly infiltrative and invasive nature of GBM requires that alternative treatments for this disease be widespread and targeted to tumor cells. Immunotherapy in the form of tumor vaccines has the potential to meet this need. Vaccines against GBM hold the promise of triggering specific and systemic antitumor immune responses that may be the key to eradicating this unrelenting cancer. In this review, we will discuss past and present clinical trials of various GBM vaccines and their potential impact on the future care of GBM patients. There have been many promising phase I and phase II GBM vaccine studies that have led to ongoing and upcoming phase III trials. If the results of these randomized trials show a survival benefit, immunotherapy will become a standard part of the treatment of this devastating disease.

Histone deacetylase inhibitor valproic acid affects plasmacytoid dendritic cells phenotype and function

OBJECTIVE

Plasmacytoid dendritic cells (PDC) represent a rare subset of dendritic cells specialized in the production of type I IFN in response to microbial pathogens. Recent data suggested that histone deacetylase (HDAC) inhibitors possess potent immunomodulatory properties both in vitro and in vivo. In this study, we assayed the ability of the HDAC inhibitor, valproic acid (VPA), to influence the phenotype and functional properties of human PDC isolated from peripheral blood.

METHODS AND RESULTS

We showed that VPA inhibited the production of IFN-α and the proinflammatory cytokines TNF-α and IL-6 by CpG-activated PDC. VPA also affected the phenotype of PDC by reducing the expression of costimulatory molecules induced by CpG activation. Moreover, VPA reduced the capacity of CpG-stimulated PDC to promote CD4(+) T cell proliferation and IFN-γ production, while enhancing the proportion of IL-10 positive T cells.

CONCLUSION

These results suggest that HDAC inhibition by VPA alters essential human PDC functions, highlighting the need for monitoring immune functions in cancer patients receiving HDAC inhibitors, but also making these drugs attractive therapies in inflammatory, and autoimmune diseases implicating PDC.

Mechanical removal of dendritic cell-generating non-classical monocytes via ex vivo lung perfusion

BACKGROUND

Ex vivo lung perfusion (EVLP) is a novel procedure designed to rapidly assess and recondition unusable donor lungs for transplantation (LTx). EVLP may reduce graft immunogenicity and allorecognition via removal of passenger leukocytes. We aimed to explore this hypothesis using human EVLP and in vitro analysis.

METHODS

Explanted human lungs (n = 7) underwent standard EVLP. Perfusate samples and the leukocyte filter were collected, and cells characterized via flow cytometry. Isolated alveolar monocytes (from post-LTx bronchoalveolar lavage) were differentiated to dendritic cells and characterized (n = 10). An in vitro (air epithelial-liquid endothelial) lung model was utilized to evaluate monocyte migration and differentiation within the lung.

RESULTS

Non-classical monocytes (NCM, normally <1% of total white blood cell repertoire) mobilized within 30 minutes of EVLP and represented 80.04% of the passenger leukocyte population. This subset readily differentiated to dendritic cells and secreted pro-inflammatory cytokines (interferon-γ and interleukin-2) after stimulation. NCM rapidly diapedesed from the vascular bed to the alveolus and, when cultured on the alveolus, differentiated to dendritic cells with inflammatory phenotypes.

CONCLUSIONS

The lung possesses a reservoir of NCM, which can readily diapedese to the alveolus or mobilize in the circulation. After activation, NCM differentiate to inflammatory dendritic cells with T-cell co-stimulatory capacity. EVLP may impart additional benefits after LTx via the removal of passenger monocytes, which may represent a previously unidentified beneficial mechanism of action.

Plasmacytoid dendritic cells engagement by influenza vaccine as a surrogate strategy for driving T-helper type 1 responses in human neonatal settings

BACKGROUND

The elicitation of T-helper type 1 (Th1) cellular immunity to eradicate intracellular pathogens is a challenging task because of the interleukin 12 (IL-12) deficit observed in early infancy.

METHODS

Screening cord blood responses to various pediatric vaccines and Toll-like receptor (TLR) agonists for innate responses and CD4(+) T-cell differentiation.

RESULTS

We identified that nonadjuvanted inactivated trivalent influenza vaccine (TIV) was able to cosignal T cells for the production of interferon γ (IFN-γ) in a neonatal setting. This process includes the mobilization of neonatal plasmacytoid dendritic cells (pDCs) as antigen-presenting cells (APCs) that efficiently engage Th1 cells in an IL-12-independent but type I IFN-dependent manner. In addition, cord blood pDCs efficiently cross-presented antigen to CD8(+) T cells. Importantly, activation by TIV mainly requires TLR7; however, R848/TLR7- and CpGB/TLR9-activated pDCs, which poorly produced IFN-α, induce neonatal Th2 responses.

CONCLUSIONS

TLR pathway engagement in pDCs is necessary but not sufficient for a successful neonatal Th1 outcome. We provide evidence of a mature and functional neonatal immune system at the level of APCs and T cells and propose to implement the IFN-α/IFN-γ axis in pediatric vaccination as a surrogate for the defective IL-12/IFN-γ axis.

Lower number of plasmacytoid dendritic cells in peripheral blood of children with bronchiolitis following respiratory syncytial virus infection

OBJECTIVES

Dendritic cells (DCs) are key mediators of allergic airway inflammation. Thus, it is important to understand the relationship between respiratory syncytial virus (RSV) infection and DCs, especially in children with RSV bronchiolitis.

METHODS

We collected peripheral blood from 71 children with RSV bronchiolitis at the time of admission and 28 children who were followed up 3 months following admission. Flow cytometry was performed to detect dendritic cell immunophenotypes.

RESULTS

Patients with RSV bronchiolitis exhibited significantly higher number of myeloid DCs and lower number of plasmacytoid DCs at the time of admission and 3 months following discharge, compared with healthy controls. These children had a significantly higher myeloid/plasmacytoid ratio 3 months after discharge compared with healthy controls.

CONCLUSIONS

Among children with RSV bronchiolitis, there is an imbalance in peripheral blood myeloid/plasmacytoid ratio. The low number of plasmacytoid DCs in peripheral blood indicates the development of bronchiolitis due to RSV infection.

Clinical studies applying cytokine-induced killer cells for the treatment of gastrointestinal tumors

Tumors of the gastrointestinal system represent a significant share of solid tumors worldwide. Despite the advances in diagnosis and treatment, the prognosis of gastrointestinal tumors is still very poor and improved therapies are indispensable. Cytokine-induced killer (CIK) cells are feasible for an immunotherapeutic approach as they are easily available and have an advantageous biologic profile; they are rapidly proliferating and their high cytotoxicity is non-MHC-restricted. We summarize and discuss twenty recent clinical studies applying CIK cells for the treatment of gastric, pancreatic, hepatocellular, and colorectal cancer. Autologous CIK cells were transfused intravenously, intraperitoneally, or via the common hepatic artery. In all studies side effects and toxicity of CIK cell therapy were mild and easily controllable. The combination of CIK cell therapy with conventional adjuvant or palliative therapies was superior to the standard therapy alone, indicating the benefit of CIK cell therapy for cancer patients. Thus, CIK cells represent a promising immunotherapy for the treatment of gastrointestinal tumors. The optimal treatment schedule and ideal combination with conventional therapies should be evaluated in further clinical studies.

Gene expression of subunits of the IL-12 family cytokines in moDCs derived in vitro from the cord blood of children of healthy and allergic mothers

The incidence of allergic diseases is steadily increasing an urgent need to clarify the immunologic processes which occur early in life and signal an increased risk of possible future allergy development. The ratio and maturation state of DCs together with the cytokine environment are important in directing and modulating immune responses. The maturation state (presence of CD83) of cord blood monocyte-derived dendritic cells (moDCs) of 52 children of healthy mothers and 58 children of allergic mothers was estimated by flow cytometry. The capacity of moDCs to express genes for subunits of IL-12 family cytokines was monitored using real-time PCR and protein secretion in cell culture supernatants by ELISA. The percentage of CD83+ moDCs was significantly higher in the allergic group after LPS stimulation (43.11 ± 4.41) in comparison to the healthy group (24.85 ± 3.37). Significantly higher gene expression of subunits of IL-12 family members was observed in moDCs of children of allergic mothers, in comparison with children of healthy mothers. The differences were evident mainly after LPS stimulation of moDCs (healthy group: p19: 3.05 ± 1.24; p28: 14.8 ± 6.8; p35: 1.8 ± 0.6; p40: 8.0 ± 3.5; EBI3: 3.0 ± 1.2; allergic group: p19: 6.1 ± 2.7; p28: 61.4 ± 22.2; p35: 14.9 ± 6.5; p40: 36.4 ± 18.8; EBI3: 11.3 ± 3.2), with the exception of p28, whose expression was significantly higher in the allergic group even without stimulation (healthy group: 0.28 ± 0.12, allergic group: 0.87 ± 0.62). No significant difference between the healthy and allergic groups was found at the protein level. The observation of both increased presence of cell surface activation marker on moDCs and higher IL-12 family gene expression in LPS-stimulated moDCs of children of allergic mothers indicates a higher reactivity of these cells.

Systemic monocyte-derived dendritic cells and associated Th2 skewing in chronic rhinosinusitis

INTRODUCTION

Monocyte-derived dendritic cells (moDCs) are antigen-presenting cells capable of directing immune responses toward T-helper 1 (Th1) or T-helper 2 (Th2) phenotypes. The systemic profile of moDCs and their association with Th1/Th2 skewing in chronic rhinosinusitis (CRS) is unclear. The purpose of this study is to characterize circulating moDCs in controls, CRS without nasal polyps (CRSsNP), and CRS with nasal polyps (CRSwNP) and correlate moDCs with Th1/Th2 skewing, mucosal inflammation on computed tomography (CT), and quality of life (QoL).

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary care hospital.

SUBJECTS

Blood was drawn from control (n = 12), CRSsNP (n = 18), and CRSwNP (n = 15) patients during endoscopic sinus surgery.

METHODS

Peripheral blood moDCs were analyzed with flow cytometry for expression of HLA-DR, CD209, and CD14. Th1 and Th2 cells were identified by CXCR3 and CCR8 expression, respectively. Lund-Mackay CT scores were assigned by blinded graders. Sino-Nasal Outcome Test 22 (SNOT-22) surveys were completed by patients before surgery.

RESULTS

CRSsNP and CRSwNP displayed elevations in systemic moDCs compared with controls. In CRSwNP, systemic Th2 skewing was observed and circulating CD4+ Th2 cells correlated with percent moDCs. MoDCs strongly correlated with higher Lund-Mackay CT scores in CRSsNP but not in CRSwNP. No relationship between moDCs and SNOT-22 scores was observed for either subset of CRS.

CONCLUSION

These data support that CRSwNP and CRSsNP display alterations in systemic immune profiles. CRSwNP is characterized by significant elevations in circulating moDCs, which is associated with systemic Th2-biased inflammation. Circulating moDCs are associated with mucosal inflammation on CT imaging in CRSsNP. No association between moDCs and QoL is evident in either CRS subset.

Maternal circulating dendritic cell subtypes at delivery and during the 1-year postpartum period

PROBLEM

Dendritic cells (DCs) play an important role in maintaining pregnancy by inducing tolerance toward the fetus. Such an immunologic change in the mother should be restored to normal after delivery, but few studies have reported postpartum maternal immune recovery, in terms of the types circulating DCs.

METHOD OF STUDY

The level of each DC subtype and HLA-DR-positive immunoreactivity of the blood from 29 pregnant women with uncomplicated labor was serially analyzed by flowcytometry at delivery and at 1.5, 6, and 12 months after delivery. DC subtypes were characterized as myeloid, lymphoid, and less differentiated (ldDC). Mean fluorescence intensity (MFI) was evaluated for HLA-DR expression for each DC subtype.

RESULTS

The total number and the percentage of DCs at delivery were lower than those at 12 months postpartum. The ldDC fractions were significantly higher at delivery and at 1.5 months than at 12 months postpartum. The MFI of HLA-DR expression on ldDCs at delivery was lower than that at 12 months postpartum. The myeloid-to-lymphoid DC ratio did not differ over the 1-year postpartum period.

CONCLUSION

The maternal alteration in DCs rapidly normalized within 1.5 months, except for the ldDC fraction, which persisted between 1.5 and 6 months after delivery.

Histamine downregulates the Th1-associated chemokine IP-10 in monocytes and myeloid dendritic cells

BACKGROUND

Histamine is an important mediator of allergic diseases. It modulates the cytokine expression of various subtypes of antigen-presenting cells by four known receptors, H1R-H4R. The effects of histamine on myeloid dendritic cells (mDC) are unclear.

METHODS

Monocytes and mDC were isolated from human PBMC. Histamine receptor expression was evaluated by real-time PCR. Cells were stimulated with histamine and histamine receptor ligands, and restimulated with polyinosinic-polycytidylic acid (poly I:C), and supernatants were analyzed by protein array and ELISA.

RESULTS

Monocytes and mDC express H1R and H2R without significant differences between the two cell types, whereas H4R mRNA was significantly higher in mDC compared with monocytes and H3R mRNA was not detected in any cell type. Prestimulation with histamine caused a significant decrease in poly I:C-induced expression of interferon-γ-induced protein (IP-10) in mDC and monocytes. Stimulation with specific H1R, H2R and H4R agonists and antagonists showed that the observed effect was mediated via H2R and H4R in monocytes and mDC.

CONCLUSION

Monocytes and mDC have similar histamine receptor repertoires with regard to H1R, H2R and H3R, but H4R expression is higher on mDC. Histamine stimulation shows similar functional effects on both cell types, i.e., downregulation of TLR3-induced IP-10 production. This might be a new mechanism how histamine fosters a Th2 milieu.

Human dendritic cell subsets

Dendritic cells are highly adapted to their role of presenting antigen and directing immune responses. Developmental studies indicate that DCs originate independently from monocytes and tissue macrophages. Emerging evidence also suggests that distinct subsets of DCs have intrinsic differences that lead to functional specialisation in the generation of immunity. Comparative studies are now allowing many of these properties to be more fully understood in the context of human immunology.

Human plasmacytoid dendritic cells: from molecules to intercellular communication network

Plasmacytoid dendritic cells (pDCs) are a specific subset of naturally occurring dendritic cells, that secrete large amounts of Type I interferon and play an important role in the immune response against viral infection. Several studies have highlighted that they are also effective antigen presenting cells, making them an interesting target for immunotherapy against cancer. However, the modes of action of pDCs are not restricted to antigen presentation and IFN secretion alone. In this review we will highlight a selection of cell surface proteins expressed by human pDCs that may facilitate communication with other immune cells, and we will discuss the implications of these molecules for pDC-driven immune responses.

Recovery of Lymphocyte and Dendritic Cell Subsets Following Reduced Intensity Allogeneic Bone Marrow Transplantation

Approaches using reduced conditioning regimens have been developed to obtain minimal procedure-related toxicity. Such novel therapeutic options are being explored with good preliminary results concerning feasibility and engraftment. However, many aspects remain under-evaluated and few data are available about immune and dendritic cell (DC) reconstitution after these highly immunosuppressive regimens. We present here our data in 20 patients receiving allogeneic bone marrow transplantation (allo-BMT) using a reduced preparative regimen. We evaluated in the first 3 months following allo-BMT, several immunological parameters including DC subsets, and compared these to historical results obtained in a group of myeloablative allo-BMT patients. We found an early recovery of leukocytes, CD8+ and NK lymphocytes. We also found a trend towards an improved B cell recovery. These results are somewhat in contrast to the altered immune recovery observed in the myeloablative setting. In addition, we found a significant early circulating DC recovery. Circulating blood DCs were also found to be of full donor origin as assessed by FISH in sex-mismatched pairs. Nevertheless, naive CD4 + CD45RA + T cells were found to be profoundly reduced following such regimens.Collectively, these data further enhance the overall benefits of reduced intensity regimens and the need for a stringent biological monitoring for assessment of the potential advantages of reduced intensity allo-BMT in comparison with conventional allo-BMT.

Inflammatory response, immunosuppression, and cancer recurrence after perioperative blood transfusions

Debate on appropriate triggers for transfusion of allogeneic blood products and their effects on short- and long-term survival in surgical and critically ill patients continue with no definitive evidence or decisive resolution. Although transfusion-related immune modulation (TRIM) is well established, its influence on immune competence in the recipient and its effects on cancer recurrence after a curative resection remains controversial. An association between perioperative transfusion of allogeneic blood products and risk for recurrence has been shown in colorectal cancer in randomized trials; whether the same is true for other types of cancer remains to be determined. This article focuses on the laboratory, animal, and clinical evidence to date on the mechanistic understanding of inflammatory and immune-modulatory effects of blood products and their significance for recurrence in the cancer surgical patient.

The dendritic cell lineage: ontogeny and function of dendritic cells and their subsets in the steady state and the inflamed setting

Dendritic cells (DCs) form a remarkable cellular network that shapes adaptive immune responses according to peripheral cues. After four decades of research, we now know that DCs arise from a hematopoietic lineage distinct from other leukocytes, establishing the DC system as a unique hematopoietic branch. Recent work has also established that tissue DCs consist of developmentally and functionally distinct subsets that differentially regulate T lymphocyte function. This review discusses major advances in our understanding of the regulation of DC lineage commitment, differentiation, diversification, and function in situ.

Human CD1c+ dendritic cells secrete high levels of IL-12 and potently prime cytotoxic T-cell responses

Dendritic cells (DC) have the unique capacities to induce primary T-cell responses. In mice, CD8α(+)DC are specialized to cross-prime CD8(+) T cells and produce interleukin-12 (IL-12) that promotes cytotoxicity. Human BDCA-3(+)DC share several relevant characteristics with CD8α(+)DC, but the capacities of human DC subsets to induce CD8(+) T-cell responses are incompletely understood. Here we compared CD1c(+) myeloid DC (mDC)1, BDCA-3(+)mDC2, and plasmacytoid DC (pDC) in peripheral blood and lymphoid tissues for phenotype, cytokine production, and their capacities to prime cytotoxic T cells. mDC1 were surprisingly the only human DC that secreted high amounts of IL-12p70, but they required combinational Toll-like receptor (TLR) stimulation. mDC2 and pDC produced interferon-λ and interferon-α, respectively. Importantly, mDC1 and mDC2 required different combinations of TLR ligands to cross-present protein antigens to CD8(+) T cells. pDC were inefficient and also expressed lower levels of major histocompatibility complex and co-stimulatory molecules. Nevertheless, all DC induced CD8(+) memory T-cell expansions upon licensing by CD4(+) T cells, and primed naive CD8(+) T cells following appropriate TLR stimulation. However, because mDC1 produced IL-12, they induced the highest levels of cytotoxic molecules. In conclusion, CD1c(+)mDC1 are the relevant source of IL-12 for naive T cells and are fully equipped to cross-prime cytotoxic T-cell responses.

Cytometry, immunology, and HIV infection: three decades of strong interactions

Flow cytometry (FCM) has been extensively used to investigate immunological changes that occur from infection with the human immunodeficiency virus (HIV). This review describes some of the most relevant cellular and molecular changes in the immune system that can be detected by FCM during HIV infection. Finally, it will be discussed how this technology has facilitated the understanding not only of the biology of the virus but also of the mechanisms that the immune system activates to fight HIV and is allowing to monitor the efficacy of antiretroviral therapy.

Dendritic cells from human mesenteric lymph nodes in inflammatory and non-inflammatory bowel diseases: subsets and function of plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDC) in mesenteric lymph nodes (MLN) may be important regulators of both inflammatory and non-inflammatory mucosal immune responses but human studies are rare. Here we compare pDC from human MLN and peripheral blood (PB) by phenotype and function. MLN from patients with or without inflammatory bowel disease (IBD) undergoing colon surgery and PB from patients with IBD and from controls were used to isolate mononuclear cells. The pDC were analysed by flow cytometry for the expression of CD40, CD80, CD83, CD86, CCR6, CCR7, CX3CR1, CD103 and HLA-DR. Purified pDC from MLN and PB were stimulated with staphylococcus enterotoxin B (SEB), CpG-A, interleukin-3 (IL-3), SEB + IL-3, CpG-A + IL-3 or left unstimulated, and cultured alone or with purified allogeneic CD4(+) CD45RA(+) HLA-DR- T cells. Subsequently, concentrations of IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, interferon-α (IFN-α), IFN-γ and tumour necrosis factor-α (TNF-α) in culture supernatants were determined by multiplex bead array. The PB pDC from IBD patients exhibited an activated and matured phenotype whereas MLN pDC and control PB pDC were less activated. CpG-A and CpG-A + IL-3-stimulated MLN pDC secreted less IL-6 and TNF-α compared with PB pDC from controls. Compared with co-cultures of naive CD4 T cells with PB pDC, co-cultures with MLN pDC contained more IL-2, IL-10 and IFN-γ when stimulated with SEB and SEB + IL-3, and less IFN-α when stimulated with CpG-A. MLN pDC differ phenotypically from PB pDC and their pattern of cytokine secretion and may contribute to specific outcomes of mucosal immune reactions.

Effects of vitamin D on immune disorders with special regard to asthma, COPD and autoimmune diseases: a short review

This paper reviews the recent data on the role of vitamin D (VD) in the genesis of various immunological disorders. It inhibits immune reactions in general, but it enhances the transcription of 'endogenous antibiotics' such as cathelicidin and defensins. VD inhibits the genesis of both Th1- and Th2-cell mediated diseases. The pleiotropic character VD-induced effects are due to the altered transcription of hundreds of genes. VD supplementation in most related studies reduced the prevalence of asthma. Th1-dependent autoimmune diseases (e.g., multiple sclerosis, Type 1 diabetes, Crohn's disease, rheumatoid arthritis and so on) are also inhibited by VD due to inhibition of antigen presentation, reduced polarization of Th0 cells to Th1 cells and reduced production of cytokines from the latter cells. VD seems to also be a useful adjunct in the prevention of allograft rejection. Last but not least, VD supplementation may be useful in the prevention or adjunct treatment of chronic obstructive pulmonary disease.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

Plasmacytoid dendritic cells and immunotherapy in multiple sclerosis

Plasmacytoid dendritic cells (pDCs) are specialized APCs implicated in the pathogenesis of many human diseases. Compared with other peripheral blood mononuclear cells, pDCs express a high level of TLR9, which recognizes viral DNA at the initial phase of viral infection. Upon stimulation, these cells produce large amounts of type I interferon and other proinflammatory cytokines and are able to prime T lymphocytes. Thus, pDCs regulate innate and adaptive immune responses. This article reviews select aspects of pDC biology relevant to the disease pathogenesis and immunotherapy in multiple sclerosis. Many unresolved questions remain in this area, promising important future discoveries in pDC research.

Increased activity of extrinsic and intrinsic apoptosis pathways in different mononuclear cell types in HIV type 1-infected patients regardless of whether they are depleted in disease

Myeloid dendritic cells (mDCs) are essential for initiation of adaptive immune responses but are depleted in HIV infection. Evidence suggests that apoptosis mediates loss, and to further understand the pathways involved, expression of caspases mediating apoptosis via the extrinsic and intrinsic pathways was analyzed. Blood samples were obtained from 14 HIV-infected patients (nine HAART and five antiretroviral naive) and 10 healthy controls. The expression of intracellular active caspases 8 and 9, associated with extrinsic and intrinsic pathways of apoptosis, and the expression of cell membrane death receptors and their ligands were assessed by flow cytometry in mDC. Additionally, expression of active caspases 8 and 9 in purified mDCs cultured for 5 days with HIV-Bal was analyzed. Frequencies of mDCs in the blood of HIV-infected patients were decreased while expression of CCR7 was up-regulated. Up to 94.4% and 91.8% of mDCs from HIV-infected patients expressed active caspases 8 and 9, respectively, compared to 24.5% and 19.9% from healthy controls (both p<0.0001). However, monocytes and B and T cells from HIV-infected patients also showed increased levels of these caspases. Percentages of FASL expression in mDCs were also elevated in HIV-infected individuals while mDCs expressing cell membrane death receptors remained unchanged. No differences between HAART and naive patients were observed for any of the molecules measured. Caspases 8 and 9 were up-regulated in mDCs cocultured with HIV despite lack of productive infection in vitro. Extrinsic and intrinsic pathways of apoptosis are up-regulated in HIV infection but do not correlate with cell depletion.

Epithelial control of the human pDC response to extracellular bacteria

Plasmacytoid pre-dendritic cells (pDCs) are specialized in responding to nucleic acids, and link innate with adaptive immunity. Although the response of pDCs to viruses is well established, whether pDCs can respond to extracellular bacteria remains controversial. Here, we demonstrate that extracellular bacteria such as Neisseria meningitidis, Haemophilus influenzae, and Staphylococcus aureus activate pDCs to produce IFN-α, TNF-α, IL-6, and to upregulate CD86 expression. We observed that pDCs were present within tonsillar crypts and oro-nasopharyngeal epithelium, where they may contact extracellular bacteria, in situ. Tonsil epithelium-conditioned supernatants inhibited IFN-α, TNF-α, and IL-6 triggered by the direct contact of N. meningitidis or S. aureus with pDCs. However, pDC priming of naive T cells was not affected, suggesting that tonsil epithelium micro-environment limits local inflammation while preserving adaptive immunity in response to extracellular bacteria. Our results reveal an important and novel function of pDCs in the initiation of the mucosal innate and adaptive immunity to extracellular bacteria.

Comparative analysis of circulating dendritic cell subsets in patients with atopic diseases and sarcoidosis

BACKGROUND

Dendritic cells (DCs) are professional antigen-presenting cells that play a crucial role in the initiation and modulation of immune responses. Human circulating blood DCs are divided into two major subsets: myeloid DCs (mDCs); and plasmacytoid DCs (pDCs). Furthermore, mDCs are subdivided into two subsets: Th1-promoting mDCs (mDC1s); and Th2-promoting mDCs (mDC2s). Although CD1a, CD1c, and CD141 are generally used for classifying mDC subsets, their adequacy as a specific marker remains unclear. We performed this study to compare circulating mDC, pDC, mDC1, and mDC2 subsets between Th1- and Th2-mediated diseases using CD1a and CD141, and to analyze the adequacy of CD1a and CD141 as a marker for mDC1s and mDC2s, respectively.

METHODS

Thirty patients with sarcoidosis, 23 patients with atopic diseases, such as atopic bronchial asthma, and 23 healthy subjects as controls were enrolled in this study. Peripheral blood DC subsets were analyzed with flow cytometry according to expressions of CD11c, CD123, CD1a, and CD141. For functional analysis, we measured interleukin (IL) 12p40 levels produced by the sorted mDC subsets.

RESULTS

The sarcoidosis group showed decreased total DC (P < 0.05) and mDC counts (P < 0.05) compared to controls. The atopy group showed decreased CD1a+mDC count (P < 0.05), and increased CD1a-mDC count (P < 0.05) compared to controls. CD141+mDC count in the atopy group was higher than controls (P < 0.05). Sorted CD1a+mDCs produced higher levels of IL-12p40 than CD1a-mDCs (P = 0.025) and CD141+mDCs (P = 0.018).

CONCLUSIONS

We conclude that decreased count of CD1a+mDC and increased count of CD141+mDC may reflect the Th2-skewed immunity in atopic diseases. The results of IL-12 levels produced by the sorted mDC subsets suggested the adequacy of CD1a and CD141 as a marker for mDC1 and mDC2, respectively, in vivo.

Expression and distribution of dendritic cells in nasal polyps

The aim of the present study was to investigate the expression, distribution and function of dendritic cells (DCs) and to study their role in nasal polyps. The study involved 55 participants, 45 of whom had nasal polyps and were the study group and 10 who had normal inferior turbinates and were the control group. Immunohistochemical staining was used to visualize the expression and distribution of the S-100 protein. A double immunostaining method was used to visualize the CD1a and CD40 expression and the images were analyzed with Axioplan 2 microscopy. The expression level of the S-100 protein in the nasal polyps was higher than that in the normal inferior turbinates with a significant difference (P<0.01). The distribution area, number and density of the double stained cells in the nasal polyps were all greater than in the normal inferior turbinates (P<0.01). The S-100 protein and double stained cells were mainly located in the lamina propria below the mucous membrane. The present study demonstrates that DCs are involved in the pathogenesis of nasal polyps and the presence of CD40-positive DCs suggests that this was related to the reciprocal interaction between the DCs and T lymphocytes.

CpG-Induced IFN-α production of plasmacytoid dendritic cells: time and dosage dependence and the effect of structural modifications to the CpG backbone

Plasmacytoid dendritic cells (pDCs) represent a highly specialized immune cell subset and are considered to be the main sentinels against viral infections and play an important role in the development of immune tolerance. pDCs are able to recognize cytosine-phosphate-guanosine (CpG) motifs within microbial DNA, which are unmethylated CG dinucleotides in a certain sequence context and trigger the secretion of interferon (IFN)-α and other proinflammatory cytokines. Here we used the typical class A CpG oligodeoxynucleotide (ODN) 2216, the B-class ODN 2006, and the newly synthesized CpG ODN TM64 to explore the potency and kinetics of IFN-α stimulation of pDC. TM64 CpG ODN has a hexanucleotide sequence TCGTGT that leads to an increased cellular uptake and features a CpG nucleotide within the sequence that leads to a potent specific B-cell stimulation, thus characteristics similar to a class B CpG. Our data reveals that all CpGs act as both dosage- and time-dependent stimuli of IFN-α secretion. The relationship between concentration of the stimulant and the secreted amount of IFN-α is not linear and results in a plateau formation, with saturation kinetics. Alteration to the backbone can change duration and quantity of overall IFN-α secretion.

Anti-immunoglobulin e therapy

The importance of immunoglobulin E (IgE) in atopic disorders such as asthma, allergic rhinitis, food allergies, and atopic dermatitis is well established. Elevation of total serum IgE is typically found in many atopic patients, and in predisposed individuals, allergen-specific IgE is produced. The availability of humanized monoclonal antibodies against IgE has provided a new therapeutic option and tool to explore the role IgE in allergic diseases and the effects of inhibiting IgE itself. Omalizumab is a humanized, monoclonal antibody that recognizes and binds to the Fc portion of the IgE molecule. Administration of omalizumab results in a rapid and substantial decrease in free IgE in serum. Consequently, the activity of cell populations involved in allergic inflammation, including mast cells, eosinophils, basophils, and antigen-presenting cells, is affected as well. Clinically, anti-IgE therapy has already been proven to be useful in the treatment of asthma and allergic rhinitis. The aim of this review is to provide an overview of the mechanisms of action of anti-IgE therapy as well as its efficacy in the treatment of allergic diseases, especially asthma. Considerations regarding dosing and safety of omalizumab will be addressed as well.

Cellular mechanism for granulocyte-colony stimulating factor in the prevention of graft-versus-host disease in combined bone marrow and peripheral blood transplantation for hematological malignancies: the composition in collection

Despite improvements in transplant immunology and clinical and supportive care, acute graft-versus-host disease (aGVHD) remains a clinical challenge and a major cause of morbidity and mortality for patients after allogeneic hematopoietic stem cell transplantation (HSCT). Many ways have been used to prevent and treat aGVHD, however, long-term survival remains poor. The key to improve aGVHD outcomes may, in fact, rest upon successful initial therapy. The HLA-matched HSCT was limited by the shortage of suitable donors. Unmanipulated haploidentical/mismatched related transplantation with combined granulocyte-colony stimulating factor (G-CSF)-mobilized peripheral blood stem cells and G-CSF-mobilized bone marrow as a stronger aGVHD inhibition and graft-versus-leukemia effect, has been developed as an alternative transplantation strategy for patients with hematologic malignancies for the advantage of immediate donor availability, ability to select the best of many relatives, controlled graft composition and immediate access to donor-derived cellular therapies if required after transplantation. G-CSF is a potent hematopoietic cytokine, which is produced by fibroblasts, monocytes, and endothelial cells. G-CSF regulates production of neutrophils within the bone marrow and affects neutrophil progenitor proliferation, maturation and is also involved in mobilization of granulocytes, stem and progenitor cells, which has an important role in this transplantation. In this article, we review the possible mechanism for this combined G-CSF-mobilized HSCT in the prevention of aGVHD. Monocytes, T cells, Tregs cells, DC, adhesive molecule, NK cell/KIR ligand mismatching and mesenchymal stem cells may be involved in this transplantation.

Depletion of plasmacytoid dendritic cells inhibits tumor growth and prevents bone metastasis of breast cancer cells

Elevated levels of plasmacytoid dendritic cells (pDC) have been reported in breast cancer patients, but the significance remains undefined. Using three immunocompetent mouse models of breast cancer bone metastasis, we identified a key role for pDC in facilitating tumor growth through immunosuppression and aggressive osteolysis. Following infiltration of macrophages upon breast cancer dissemination, there was a steady increase in pDC within the bone, which resulted in a sustained Th2 response along with elevated levels of regulatory T cells and myeloid-derived suppressor cells. Subsequently, pDC and CD4(+) T cells, producing osteolytic cytokines, increased with tumor burden, causing severe bone damage. Microcomputed tomography and histology analyses of bone showed destruction of femur and tibia. The therapeutic significance of this finding was confirmed by depletion of pDC, which resulted in decreased tumor burden and bone loss by activating tumor-specific cytolytic CD8(+) T cells and decreasing suppressor cell populations. Thus, pDC depletion may offer a novel adjuvant strategy to therapeutically influence breast cancer bone metastasis.

Bone marrow dendritic cell-mediated regulation of TLR and B cell receptor signaling in B cells

Dendritic cells (DCs) play an essential role in regulation of immune responses. In the periphery, Ag presentation by DCs is critical for adaptive responses; for this reason, DCs are often targets of adjuvants that enhance vaccine responses. Activated mature DCs enhance B cell activation and differentiation by providing cytokines like BAFF and a proliferation-inducing ligand. However, the role of immature DCs in B cell tolerance is not well studied. Recently, mouse immature bone marrow-derived DCs (iBMDCs) have been shown to suppress anti-IgM-induced B cell activation. In this study, we tested the ability of mouse DCs to modulate B cell functions during TLR activation. We found that iBMDCs potently suppressed proliferation and differentiation of various B cell subsets on TLR stimulation. However, iBMDCs did not affect CD40-mediated B cell activation. Optimal suppression of B cell activation by iBMDCs required cell contact via the CD22 receptor on B cells. The B cell suppression was a property of iBMDCs or DCs resident in the bone marrow (BM), but not mature BM-derived DCs or DCs resident in the spleen. Presence of iBMDCs also enhanced the Ag-induced apoptotic response of BM B cells, suggesting that the suppressive effects of iBMDCs may have a role in B cell tolerance.

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.

New paradigms in type 2 immunity

Nearly half of the world's population harbors helminth infections or suffers from allergic disorders. A common feature of this population is the so-called "type 2 immune response," which confers protection against helminths, but also promotes pathologic responses associated with allergic inflammation. However, the mechanisms that initiate and control type 2 responses remain enigmatic. Recent advances have revealed a role for the innate immune system in orchestrating type 2 responses against a bewildering array of stimuli, from nanometer-sized allergens to 20-meter-long helminth parasites. Here, we review these advances and suggest that the human immune system has evolved multiple mechanisms of sensing such stimuli, from recognition of molecular patterns via innate immune receptors to detecting metabolic changes and tissue damage caused by these stimuli.

Primary vaccination with low dose live dengue 1 virus generates a proinflammatory, multifunctional T cell response in humans

The four dengue virus serotypes (DENV-1-DENV-4) have a large impact on global health, causing 50-100 million cases of dengue fever annually. Herein, we describe the first kinetic T cell response to a low-dose DENV-1 vaccination study (10 PFU) in humans. Using flow cytometry, we found that proinflammatory cytokines, IFNγ, TNFα, and IL-2, were generated by DENV-1-specific CD4(+) cells 21 days post-DENV-1 exposure, and their production continued through the latest time-point, day 42 (p<0.0001 for all cytokines). No statistically significant changes were observed at any time-points for IL-10 (p = 0.19), a regulatory cytokine, indicating that the response to DENV-1 was primarily proinflammatory in nature. We also observed little T cell cross-reactivity to the other 3 DENV serotypes. The percentage of multifunctional T cells (T cells making ≥ 2 cytokines simultaneously) increased with time post-DENV-1 exposure (p<0.0001). The presence of multifunctional T cells together with neutralizing antibody data suggest that the immune response generated to the vaccine may be protective. This work provides an initial framework for defining primary T cell responses to each DENV serotype and will enhance the evaluation of a tetravalent DENV vaccine.

Dendritic cell-mediated vaccination relies on interleukin-4 receptor signaling to avoid tissue damage after Leishmania major infection of BALB/c mice

Prevention of tissue damages at the site of Leishmania major inoculation can be achieved if the BALB/c mice are systemically given L. major antigen (LmAg)-loaded bone marrow-derived dendritic cells (DC) that had been exposed to CpG-containing oligodeoxynucleotides (CpG ODN). As previous studies allowed establishing that interleukin-4 (IL-4) is involved in the redirection of the immune response towards a type 1 profile, we were interested in further exploring the role of IL-4. Thus, wild-type (wt) BALB/c mice or DC-specific IL-4 receptor alpha (IL-4Rα)-deficient (CD11c^creIL-4Rα^−/lox) BALB/c mice were given either wt or IL-4Rα-deficient LmAg-loaded bone marrow-derived DC exposed or not to CpG ODN prior to inoculation of 2×10⁵ stationary-phase L. major promastigotes into the BALB/c footpad. The results provide evidence that IL4/IL-4Rα-mediated signaling in the vaccinating DC is required to prevent tissue damage at the site of L. major inoculation, as properly conditioned wt DC but not IL-4Rα-deficient DC were able to confer resistance. Furthermore, uncontrolled L. major population size expansion was observed in the footpad and the footpad draining lymph nodes of CD11c^creIL-4Rα^−/lox mice immunized with CpG ODN-exposed LmAg-loaded IL-4Rα-deficient DC, indicating the influence of IL-4Rα-mediated signaling in host DC to control parasite replication. In addition, no footpad damage occurred in BALB/c mice that were systemically immunized with LmAg-loaded wt DC doubly exposed to CpG ODN and recombinant IL-4. We discuss these findings and suggest that the IL4/IL4Rα signaling pathway could be a key pathway to trigger when designing vaccines aimed to prevent damaging processes in tissues hosting intracellular microorganisms.

Cutaneous leishmaniasis is endemic in tropical and subtropical regions of the world. Effective vaccination strategies are urgently needed because of the emergence of drug-resistant parasites and severe side effects of chemotherapy. We previously established a DC-based vaccination strategy to induce complete and long-lasting immunity to experimental leishmaniasis using Leishmania major antigen-loaded and CpG oligodeoxynucleotide-activated DC as a vaccine carrier. In the present study we investigated the role of IL-4Rα-mediated instruction of the vaccinating DC and the host DC during induction of protection against leishmaniasis. The results demonstrate that IL-4Rα signaling in DC used as vaccine carrier plays an important role in induction of protective immunity against L. major infection, as only mice vaccinated with IL-4 responder DC are able to trigger effective Th1-mediated immunity. The immunity is hallmarked by high levels of L. major-induced bioactive IL-12 production in the lymph nodes of vaccinated mice. Together, these findings suggest that IL-4 is a strong adjuvant to induce Th1-biased immunity against leishmaniasis and possibly other infections with intracellular pathogens, indicating that IL-4 needs to be considered in the development of efficient cell-mediated vaccination strategies.

Interaction of Hepatitis C virus proteins with pattern recognition receptors

Hepatitis C virus (HCV) is an important human pathogen that causes acute and chronic hepatitis, cirrhosis and hepatocellular carcinoma worldwide. This positive stranded RNA virus is extremely efficient in establishing persistent infection by escaping immune detection or hindering the host immune responses. Recent studies have discovered two important signaling pathways that activate the host innate immunity against viral infection. One of these pathways utilizes members of Toll-like receptor (TLR) family and the other uses the RNA helicase retinoic acid inducible gene I (RIG-I) as the receptors for intracellular viral double stranded RNA (dsRNA), and activation of transcription factors. In this review article, we summarize the interaction of HCV proteins with various host receptors/sensors through one of these two pathways or both, and how they exploit these interactions to escape from host defense mechanisms. For this purpose, we searched data from Pubmed and Google Scholar. We found that three HCV proteins; Core (C), non structural 3/4 A (NS3/4A) and non structural 5A (NS5A) have direct interactions with these two pathways. Core protein only in the monomeric form stimulates TLR2 pathway assisting the virus to evade from the innate immune system. NS3/4A disrupts TLR3 and RIG-1 signaling pathways by cleaving Toll/IL-1 receptor domain-containing adapter inducing IFN-beta (TRIF) and Cardif, the two important adapter proteins of these signaling cascades respectively, thus halting the defense against HCV. NS5A downmodulates the expressions of NKG2D on natural killer cells (NK cells) via TLR4 pathway and impairs the functional ability of these cells. TLRs and RIG-1 pathways have a central role in innate immunity and despite their opposing natures to HCV proteins, when exploited together, HCV as an ever developing virus against host immunity is able to accumulate these mechanisms for near unbeatable survival.

Campylobacter jejuni-mediated induction of CC and CXC chemokines and chemokine receptors in human dendritic cells

Campylobacter jejuni is a leading worldwide bacterial cause of human diarrheal disease. Although the specific molecular mechanisms of C. jejuni pathogenesis have not been characterized in detail, host inflammatory responses are thought to be major contributing factors to the resulting typical acute colitis. The intestinal mucosal chemokine response is particularly important in the initial stages of bacterium-induced gut inflammation. Chemokines attract blood phagocytes and lymphocytes to the site of infection and regulate immune cell maturation and the development of localized lymphoid tissues. The production of chemokines by dendritic cells (DCs) following Campylobacter infection has not yet been analyzed. In the current study, we infected human monocyte-derived DCs with C. jejuni to examine the production of key proinflammatory chemokines and chemokine receptors. The chemokines, including CC families (macrophage inflammatory protein 1α [MIP-1α], MIP-1β, RANTES) and CXC families (growth-related oncogene α [GRO-α], IP-10, and monokine induced by gamma interferon [MIG]), were upregulated in Campylobacter-infected DCs. Chemokine receptors CCR6 and CCR7, with roles in DC trafficking, were also induced in Campylobacter-infected DCs. Further, Campylobacter infection stimulated the phosphorylation of P38, P44/42, and stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK) mitogen-activated protein kinases (MAPKs) in DCs. NF-κB activation was specifically involved in chemokine induction in DCs infected with C. jejuni. Additionally, STAT3 was significantly increased in Campylobacter-infected DCs compared to that in uninfected DCs. These results suggest that DCs play a significant role in the initiation and modulation of the inflammatory response by enlisting monocytes, neutrophils, and T lymphocytes during human intestinal infection with Campylobacter.

Multiple sclerosis-linked and interferon-beta-regulated gene expression in plasmacytoid dendritic cells

The cause of multiple sclerosis (MS) is not known and the mechanism of interferon-beta, a disease-modifying treatment, is not well-understood. We studied gene expression in plasmacytoid dendritic cells (pDCs), antigen-presenting cells implicated in MS pathogenesis. PDCs were separated from healthy donors and MS patients at two time points: before and after initiation of treatment with interferon-beta. Expression of selected MS-linked and interferon-beta-regulated genes was validated with single assays. We have identified 60 genes which were abnormally expressed in MS patients and were corrected after treatment. These genes could be studied as potential MS biomarkers and possible therapeutic targets in MS.

Plasmacytoids dendritic cells are a therapeutic target in anticancer immunity

Dendritic cells (DCs) are immunological sentinels of the organism acting as antigen-presenting cells (APC) and are critical for induction of innate and adaptive immunity. Traditionally they are divided in myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs), a rare population of circulating cells that selectively express Toll-like receptors (TLR) 7 and TLR9 and have the capacity to produce large amounts of type I interferons (IFNs) in response to pathogenic agents or danger signals. It has been demonstrated that pDCs can coordinate events during the course of viral infections, allergic and autoimmune diseases and cancer. Through the production of type I IFNs, pDCs initiate protective immunity by activating classical DCs, T cells, natural killer cells and B cells. Upon activation, pDCs also differentiate into mature DCs and may contribute to the contraction of T-cell response. Human pDCs preferentially express immunoglobulin-like transcript 7 (ILT7; LILRA4), which couples with a signaling adapter to activate a prominent immune-receptor tyrosine-based activation motif (ITAM)-mediated signaling pathway. The interaction between ILT7 and bone marrow stromal cell antigen 2 (BST2, CD317) assures an appropriate TLR response by pDCs during viral infections and likely participates in pDCs tumor crosstalk. Moreover these cells seem to play a crucial role in the initiation of the pathological process of autoimmune diseases such as lupus or psoriasis. Despite the fact that their function within a tumor context is still controversial they represent an attractive target for therapeutic manipulation of the immune system to elicit a powerful immune response against tumor antigens in combination with other therapies.

Therapeutic vaccines against HIV infection

Resistance to medication, adverse effects in the medium-to-long-term and cost all place important limitations on lifelong adherence to combined antiretroviral therapy (cART). In this context, new therapeutic alternatives to 'cART for life' in HIV-infected patients merit investigation. Some data suggest that strong T cell-mediated immunity to HIV can indeed limit virus replication and protect against CD4 depletion and disease progression. The combination of cART with immune therapy to restore and/or boost immune-specific responses to HIV has been proposed, the ultimate aim being to achieve a 'functional cure'. In this scenario, new, induced, HIV-specific immune responses would be able to control viral replication to undetectable levels, mimicking the situation of the minority of patients who control viral replication without treatment and do not progress to AIDS. Classical approaches such as whole inactivated virus or recombinant protein initially proved useful as therapeutic vaccines. Overall, however, the ability of these early vaccines to increase HIV-specific responses was very limited and study results were discouraging, as no consistent immunogenicity was demonstrated and there was no clear impact on viral load. Recent years have seen the development of new approaches based on more innovative vectors such as DNA, recombinant virus or dendritic cells. Most clinical trials of these new vectors have demonstrated their ability to induce HIV-specific immune responses, although they show very limited efficacy in terms of controlling viral replication. However, some preliminary results suggest that dendritic cell-based vaccines are the most promising candidates. To improve the effectiveness of these vaccines, a better understanding of the mechanisms of protection, virological control and immune deterioration is required; without this knowledge, an efficacious therapeutic vaccine will remain elusive.

Innate immunity in atopic dermatitis

Atopic dermatitis (AD) is a clinically defined, highly pruritic, chronic inflammatory skin disease. In AD patients, the combination of a genetic predisposition for skin barrier dysfunction and dysfunctional innate and adaptive immune responses leads to a higher frequency of bacterial and viral skin infections. The innate immune system quickly mobilizes an unspecific, standardized first-line defense against different pathogens. Defects in this system lead to barrier dysfunction which results in increased protein allergen penetration through the epidermis and predisposes to secondary skin infections. Two loss-of-function mutations in the epidermal filaggrin gene are associated with AD. Also, inducible endogenous antibiotics such as the antimicrobial peptides cathelicidin and the beta-defensins may show defective function in lesional AD skin. Eczema herpeticum is a disseminated viral infection almost exclusively diagnosed in AD patients, which is based on unmasking of the viral entry receptor nectin-1, lack of cathelicidin production by keratinocytes, and depletion of Type I IFN-producing plasmacytoid dendritic cells from AD skin. Future therapeutic approaches to AD may include enhancement of impaired innate in addition to downregulation of dysfunctional adaptive immunity.

Enveloped virus but not bacteria block IL-13 responses in human cord blood T cells in vitro

Infections that occur early in life may have a beneficial effect on the immune system and thereby reduce the risk of allergen sensitization and/or allergic disease. It is not yet clear to what extent specific virus and/or bacteria can mediate this effect. The purpose of this study was to assess the role of virus and bacteria in CD4⁺ T cell‐derived cytokine production in newborns. We compared the effects of five bacteria (Staphlococcus aureus, Escherichia coli, Clostridium difficile, Lactobacillus rhamnosus and Bifidobacterium bifidus) and seven virus (adenovirus, coronavirus, cytomegalovirus, herpes simplex virus, influenza virus, morbillivirus and poliovirus) on the Th1/Th2 cytokine production in mixed lymphocyte reactions using CD4⁺ T cells from cord blood cocultured with allogenic myeloid or plasmacytoid dendritic cells. When comparing the baseline cytokine production prior to microbial stimulation, we observed that cord plasmacytoid DC were stronger inducers of Th2 cytokines (IL‐5 and IL‐13) compared with cord myeloid DC and to adult DC. When adding microbes to these cultures, bacteria and virus differed in two major respects; Firstly, all enveloped viruses, but none of the bacteria, blocked Th2 (IL‐13) production by cord CD4⁺ cells. Secondly, all Gram‐positive bacteria, but none of the virus, induced IL‐12p40 responses, but the IL‐12p40 responses did not affect Th1 cytokine production (IFN‐γ). Instead, Th1 responses were correlated with the capacity to induce IFN‐α secretion, which in cord cells were induced by S. aureus and influenza virus alone. These data imply that enveloped virus can deviate Th2 responses in human cord T cells.

Generation of immunogenic and tolerogenic clinical-grade dendritic cells

Immunotherapy with dendritic cells (DCs), which have been manipulated ex vivo to become immunogenic or tolerogenic, has been tested in clinical trials for disease therapy. DCs are sentinels of the immune system, which after exposure to antigenic or inflammatory signals and crosstalk with effector CD4(+) T cells express high levels of costimulatory molecules and cytokines. Upregulation of either costimulatory molecules or cytokines promotes immunologic DCs, whereas their downregulation generates tolerogenic DCs (TDCs), which induce T regulatory cells (Tregs) and a state of tolerance. Immunogenic DCs are used for the therapy of infectious diseases such as HIV-1 and cancer, whereas tolerogenic DCs are used in treating various autoimmune diseases and in transplantation. DC vaccination is still at an early stage, and improvements are mainly needed in quality control of monitoring assays to generate clinical-grade DC products and to assess the effect of DC vaccination in future clinical trials. Here, we review the recent work in DC generation and monitoring approaches for DC-based trials with immunogenic or tolerogenic DCs.