Antigen Uptake Capacity Research Articles

Functional Impairment of Murine Dendritic Cell Subsets following Infection with Infective Larval Stage 3 of Brugia malayi.

Filarial parasites cause functional impairment of host dendritic cells (DCs). However, the effects of early infection on individual DC subsets are not known. In this study, we infected BALB/c mice with infective stage 3 larvae of the lymphatic filarial parasite Brugia malayi (Bm-L3) and studied the effect on fluorescence-activated cell sorter (FACS)-sorted DC subsets. While myeloid DCs (mDCs) accumulated by day 3 postinfection (p.i.), lymphoid DCs (LDCs) and CD8+ plasmacytoid DCs (pDCs) peaked at day 7 p.i. in the spleens and mesenteric lymph nodes (mLNs) of infected mice. Increased tumor necrosis factor alpha (TNF-α) but reduced interleukin 12 (IL-12) and Toll-like receptor 4 (TLR4), -6, and -9 and reciprocal secretion of IL-4 and IL-10 were also observed across all DC subsets. Interestingly, Bm-L3 increased the expression of CD80 and CD86 across all DC subsets but decreased that of major histocompatibility complex class II (MHC-II) on mDCs and pDCs, resulting in their impaired antigen uptake and presentation capacities, but maximally attenuated the T-cell proliferation capacity of only mDCs. Furthermore, Bm-L3 increased phosphorylated p38 (p-p38), but not p-ERK, in mDCs and LDCs but downregulated them in pDCs, along with differential modulation of protein tyrosine phosphatases SHP-1, TCPTP, PTEN, and PTP1B across all DC subsets. Taken together, we report hitherto undocumented effects of early Bm-L3 infection on purified host DC subsets that lead to their functional impairment and attenuated host T-cell response.

The Role of PKM2 in the Activation of Myeloid Dendritic Cells from Patients with Severe Aplastic Anemia

Severe aplastic anemia (SAA) is a hematologic disease characterized by severe bone marrow failure. The abnormal activation of myeloid dendritic cells (mDCs) in SAA might accelerate the polarization of Th0 cells to Th1 cells ,thus causing the over-function of T lymphocytes and apoptosis of hematopoietic cells. Hence, mDCs played an important role in the primary stage of the immune response.Here, we analyze the protein components of mDC from SAA as well as normal control to explore the possible reason that activate mDC. The protein components of mDCs was detected by proteomics technology. Furtherly we applied both realtime PCR and western blot from a perspective of mRNA and protein to validate our discovery. Results revealed that expression of pyruvate kinase M2(PKM2) were enhanced in mDCs from SAA patients at an early stage of the onset. Concurrently, the level of PKM2 in mDCs of SAA patients was conspicuously higher than that in normal control not only at a protein level but also at the gene level.To clarify the role of PKM2 in the activation of mDCs, we investigate the effect of targeted PKM2 siRNA -knockout in mDCs at the cellular level. We measured the levels of costimulatory molecules CD80 and CD86 on mDCs by flow cytometry and identified significantly higher expression of CD86 in the control group relative to the transfected group.To quantify antigen uptake and processing capacities of mDCs, cells were treated with carboxylate-modified yellow-green (YG) microspheres and then analyzed by flow cytometry. The percentage of phagocytosis (PP) was determined by the following formula: PP = M1 + M2 + M3 + M4, where M1, M2, M3, and M4 correspond to the number of cells with one, two, three and four microspheres. Phagocytosis index(PI)=(intracellular cpms/ intracellular + extracellular cpms)x100%.After PKM2 siRNA transfection, we observed lower phagocytic ability of mDCs. Additionally, the level of PP of mDCs from control group was higher than that of PKM2 siRNA -knockout group. Through scanning electron microscopy (SEM), mDCs before siRNA transfection from SAA patients presented longer and more branched protrusions than those seen in PKM2 siRNA transfected mDCs.Next, the effects of PKM2 on cytotoxic T cells(CTL) activation by mDCs from SAA patients were also determined. mDCs before and after PKM2 siRNA transfection were co cultured with CTL cells for 72 hours. After cell co culture, the mRNA expressions of perforin were identified significantly higher in the control group relative to the transfected group. Culture supernatant were collected for quantification of IFN-γ and IL-4 by commercial ELISA kits. The levels of IFN-γ and IL-4 in contral group were much higher than that of transfected group .Additionally, flow cytometry experiments assessing annexin V/propidium iodide staining showed that high PKM2 expression in mDCs was significantly associated with reduced apoptosis rate of CTLs. Therefore, the enhanced function of mDCs from SAA could activate the downstream CTL function and then enhance the killing effect to target cells.Our findings demonstrated that elevated levels of PKM2 in mDCs play an important role in the activation of mDCs and thereby affecting the immune status of SAA by enhancing the function of mDCs and downstream CTLs. DisclosuresNo relevant conflicts of interest to declare.

Human 15-lipoxygenase-1 is a regulator of dendritic-cell spreading and podosome formation.

Dendritic cells (DCs) involved in proinflammatory immune responses derive mainly from peripheral monocytes, and the cells subsequently mature and migrate into the inflammatory micromilieu. Here we report that suppressing of 15-lipoxygenase-1 led to a substantial reduction in DC spreading and podosome formation in vitro. The surface expression of CD83 was significantly lower in both sh-15-lipoxygenase-1 (15-LOX-1)-transduced cells and DCs cultivated in the presence of a novel specific 15-LOX-1 inhibitor. The T-cell response against tetanus-pulsed DCs was only affected to a minor extent on inhibition of 15-LOX-1. In contrast, endocytosis and migration ability of DCs were significantly suppressed on 15-LOX-1 inhibition. The expression of 15-LOX-1 in DCs was also demonstrated in affected human skin in atopic and contact dermatitis, showing that the enzyme is indeed expressed in inflammatory diseases in vivo. This study demonstrated that inhibiting 15-LOX-1 led to an impaired podosome formation in DCs, and consequently suppressed antigen uptake and migration capacity. These results indicated that 15-LOX-1 is a potential target for inhibiting the trafficking of DCs to lymphoid organs and inflamed tissues and decreasing the inflammatory response attenuating symptoms of certain immunologic and inflammatory disorders such as dermatitis.-Han, H., Liang, X., Ekberg, M., Kritikou, J. S., Brunnström, Å., Pelcman, B., Matl, M., Miao, X., Andersson, M., Yuan, X., Schain, F., Parvin, S., Melin, E., Sjöberg, J., Xu, D., Westerberg, L. S., Björkholm, M., Claesson, H.-E. Human 15-lipoxygenase-1 is a regulator of dendritic-cell spreading and podosome formation.

BTLA-expressing CD11c antigen presenting cells in patients with active tuberculosis exhibit low capacity to stimulate T cell proliferation

Despite past extensive studies on B and T lymphocyte attenuator (BTLA)-mediated negative regulation of T cell activation, the role of BTLA in antigen presenting cells (APCs) in patients with active pulmonary tuberculosis (ATB) remains poorly understood. Here, we demonstrate that BTLA expression on CD11c APCs increased in patients with ATB. Particularly, BTLA expression in CD11c APCs was likely associated with the attenuated stimulatory capacity on T cells (especially CD8+ T cell) proliferation. BTLA-expressing CD11c APCs showed lower antigen uptake capacity, lower CD86 expression, higher HLA-DR expression, and enhanced IL-6 secretion, compared to counterpart BTLA negative CD11c APCs in healthy controls (HC). Interestingly, BTLA-expressing CD11c APCs from ATB patients displayed lower expression of HLA-DR and less IL-6 secretion, but higher expression of CD86 than those from HC volunteers. Mixed lymphocyte reaction suggests that BTLA expression is likely associated with positive rather than conventional negative regulation of CD11c APCs stimulatory capacity. This role is impaired in ATB patients manifested by low expression of HLA-DR and low production of IL-6. This previous unappreciated role for BTLA may have implications in the prevention and treatment of patients with ATB.

Phenotypic and Functional Properties of Human Steady State CD14+ and CD1a+ Antigen Presenting Cells and Epidermal Langerhans Cells.

Cutaneous antigen presenting cells (APCs) are critical for the induction and regulation of skin immune responses. The human skin contains phenotypically and functionally distinct APCs subsets that are present at two separated locations. While CD1ahigh LCs form a dense network in the epidermis, the CD14+ and CD1a+ APCs reside in the dermal compartment. A better understanding of the biology of human skin APC subsets is necessary for the improvement of vaccine strategies that use the skin as administration route. In particular, progress in the characterization of uptake and activatory receptors will certainly improve APC-targeting strategies in vaccination. Here we performed a detailed analysis of the expression and function of glycan-binding and pattern-recognition receptors in skin APC subsets. The results demonstrate that under steady state conditions human CD1a+ dermal dendritic cells (DCs) were phenotypically most mature as measured by the expression of CD83 and CD86, whereas the CD14+ cells showed a higher expression of the CLRs DC-SIGN, mannose receptor and DCIR and had potent antigen uptake capacity. Furthermore, steady state LCs showed superior antigen cross-presentation as compared to the dermal APC subsets. Our results also demonstrate that the TLR3 ligand polyribosinic-polyribocytidylic acid (pI:C) was the most potent stimulator of cytokine production by both LCs and dDCs. These studies warrant further exploration of human CD1a+ dDCs and LCs as target cells for cancer vaccination to induce anti-tumor immune responses.

Cigarette smoke differentially modulates dendritic cell maturation and function in time.

BackgroundDendritic cells (DCs) as professional antigen presenting cells (APCs) play a critical role in the regulation of host immune responses. DCs evolve from immature, antigen-capturing cells, to mature antigen-presenting cells. The relative contribution of DCs to cigarette smoke-induced inflammation is not well documented. In the current study, we investigated a modulatory effect of cigarette smoke extract (CSE) on differentiation, maturation and function of DCs.MethodsPrimary murine DCs were grown from bone marrow cells with GM-CSF. Development of DC was analyzed by expression of CD11c, MHCII, CD86, CD40 and CD83 using flow cytometry. Murine DC’s and human L428 cells were co-cultured with CSE for various periods of time. Functional activity was analyzed by measuring FITC-dextran uptake, cytokine production and the ability to stimulate T cell activation in a mixed lymphocyte reaction.ResultsOur results show that short-term CSE stimulation (~24 h) influence the maturation status of newly differentiated and immature DCs towards more mature cells as revealed by upregulation of MHCII, CD83, CD86, CD40, reduction in antigen up-take capacity and enhanced secretion of pro-inflammatory (IL-12, IL-6 and TNF-α) cytokines. Interestingly, long-term CSE exposure, time- and concentration-dependently, suppressed the development of functional DCs. This suppression was demonstrated by a decline in CD11c/MHCII, CD83, CD86 and CD40 expression, the production of cytokines and ability to stimulate T lymphocytes. Moreover, CSE significantly suppressed the endocytosis function of mouse DCs which was not due to diminished DC viability. Similar to mouse DCs, long-term co-culturing of the human L428 DC cell line with CSE time-dependently suppressed the expression of CD54.ConclusionsThe present study provides evidence that CSE modulates DC-mediated immune responses via affecting both the function and maturation of DCs. The suppressive effects of cigarette smoke on DC function might lead to impaired immune responses to various infections.Electronic supplementary materialThe online version of this article (doi:10.1186/s12931-015-0291-6) contains supplementary material, which is available to authorized users.

Microfluidic squeezing for intracellular antigen loading in polyclonal B-cells as cellular vaccines.

B-cells are promising candidate autologous antigen-presenting cells (APCs) to prime antigen-specific T-cells both in vitro and in vivo. However to date, a significant barrier to utilizing B-cells as APCs is their low capacity for non-specific antigen uptake compared to “professional” APCs such as dendritic cells. Here we utilize a microfluidic device that employs many parallel channels to pass single cells through narrow constrictions in high throughput. This microscale “cell squeezing” process creates transient pores in the plasma membrane, enabling intracellular delivery of whole proteins from the surrounding medium into B-cells via mechano-poration. We demonstrate that both resting and activated B-cells process and present antigens delivered via mechano-poration exclusively to antigen-specific CD8+T-cells, and not CD4+T-cells. Squeezed B-cells primed and expanded large numbers of effector CD8+T-cells in vitro that produced effector cytokines critical to cytolytic function, including granzyme B and interferon-γ. Finally, antigen-loaded B-cells were also able to prime antigen-specific CD8+T-cells in vivo when adoptively transferred into mice. Altogether, these data demonstrate crucial proof-of-concept for mechano-poration as an enabling technology for B-cell antigen loading, priming of antigen-specific CD8+T-cells, and decoupling of antigen uptake from B-cell activation.

Latency-Associated Protein Acr1 Impairs Dendritic Cell Maturation and Functionality: A Possible Mechanism of Immune Evasion by Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tuberculosis) in latently infected individuals survives and thwarts the attempts of eradication by the immune system. During latency, Acr1 is predominantly expressed by the bacterium. However, whether M. tuberculosis exploits its Acr1 in impairing the host immunity remains widely unexplored. Hence, currently we have investigated the role of Acr1 in influencing the differentiation and function of dendritic cells (DCs), which play a cardinal role in innate and adaptive immunity. Therefore, for the first time, we have revealed a novel mechanism of mycobacterial Acr1 in inhibiting the maturation and differentiation of DCs by inducing tolerogenic phenotype by modulating the expression of PD-L1; Tim-3; indoleamine 2, 3-dioxygenase (IDO); and interleukin 10. Furthermore, Acr1 interferes in the differentiation of DCs by targeting STAT-6 and STAT-3 pathways. Continuous activation of STAT-3 inhibited the translocation of NF-κB in Acr1-treated DCs. Furthermore, Acr1 also augmented the induction of regulatory T cells. These DCs displayed decline in their antigen uptake capacity and reduced ability to help T cells. Interestingly, M. tuberculosis exhibited better survival in Acr1-treated DCs. Thus, this study provides a crucial insight into a strategy adopted by M. tuberculosis to survive in the host by impairing the function of DCs.

A unique case of dendritic cell neoplasm from monocyte-derived myeloid origin with distinct immunophenotype and cytomorphology

Dear Editor, Two distinct subsets of circulating dendritic cells (DCs) have been identified: myeloid (CD11cCD123) DCs and lymphoid or plasmacytoid (CD11cCD123) DCs [1]. Here, we demonstrate an unusual dendritic cell neoplasm presenting the acute leukemic phase, and thought to originate from monocyte-derived circulating myeloid DCs (mDC). A 69-year-old woman with a history of essential thrombocythemia was evaluated for fever and respiratory failure. The patient was diagnosed 11 years earlier and was treated at varying intervals with hydroxyurea. A computed tomography scan demonstrated hepatosplenomegaly with multiple lymphadenopathy. A few days later, cytopenia had progressed: white blood cell count, 8.8×10/L; hemoglobin, 9.0 g/dL; and platelet count, 34×10/L. In a peripheral blood smear, 25 % of the lymphoid cells were medium to large and had irregular nuclear outlines, indistinct nucleoli, basophilic cytoplasm, minimal granules, and some membrane protrusions (Fig. 1a). Flow cytometry showed a CD45 population expressing CD4 and CD56. There was no B cell, T cell, or myeloid expression except for CD2 and CD11c (partial), and no expression of CD34, terminal deoxynucleotidyl transferase or killer cell immunoglobulin-like receptors on natural killer (NK) cells. The cells diffusely infiltrated the bone marrow (Fig. 1b). Immunohistochemistry was positive for CD56, but negative for CD123 and myeloperoxidase (Fig. 1c, d). Diffuse bone marrow fibrosis was evident by reticulin and Masson’s trichrome stains (Fig. 1e, f). Based on these features, the cells were considered to most likely be monocyte-derived mDCs. Infectious pathogens which have been linked to the genesis of hematologic malignancy, such as Epstein–Barr virus and human T cell lymphotropic virus type I, were excluded. The karyotype showed complex structural and numerical abnormalities, 45,XX,+1,dic(1;15)(p13;q22),-16,-19,+mar1[15]/45,sl,13,+mar2 [5]. The patient’s condition rapidly worsened during her hospital stay. Marked leukocytosis (144×10/L) with abnormal cells (72 %) was noted in peripheral blood. Despite first cycle chemotherapy, she expired due to respiratory failure combined with septic shock after only 3 weeks of hospitalization. Two DC subsets can arise from common hematopoietic stem cells in the bone marrow; however, mDCs and plasmacytoid DCs (pDCs) are phenotypically and functionally different. mDCs are monocytoid in appearance with a characteristically hyperlobulated nucleus and express myeloidassociated antigens, whereas pDCs possess a more rounded morphology with an oval nucleus and express lymphoidassociated antigens [1]. Both DC subsets are potent stimulators of allogeneic lymphocytes, but mDCs predominantly prime a T helper type I cell antimicrobial response, whereas pDCs seem to support the generation of a T helper type II cell response [2]. Furthermore, mDCs are known to have a higher capacity for antigen uptake and presenting capacity than pDCs [1]. Other immunophenotypic markers including CD2 and CD7 have been used to further classify circulating DC subsets. Strong CD2 expression has been suggested to define mDC differentiation from monocyte precursors [3] and CD7 and CD56 coexpression may be a very useful marker for discrimination monocyte-derived mDCs from NK cells [4, 5]. In summary, this case suggests that a circulating myeloid DC subset could alsomanifest as leukemiawith an aggressive clinical course. However, these cells have a distinct immunophenotype M.<A. Jang : S.<T. Lee : S.<H. Kim (*) Department of LaboratoryMedicine and Genetics, SamsungMedical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 135-710, South Korea e-mail: drsunnyhk@gmail.com

Egr2 induced during DC development acts as an intrinsic negative regulator of DC immunogenicity

Early growth response gene 2 (Egr2), which encodes a zinc finger transcription factor, is rapidly and transiently induced in various cell types independently of de novo protein synthesis. Although a role for Egr2 is well established in T-cell development, Egr2 expression and its biological function in dendritic cells (DCs) have not yet been described. Here, we demonstrate Egr2 expression during DC development, and its role in DC-mediated immune responses. Egr2 is expressed in the later stage of DC development from BM precursor cells. Even at steady state, Egr2 is highly expressed in mouse splenic DCs. Egr2-knockdown (Egr2-KD) DCs showed increased levels of major histocompatability complex (MHC) class I and II and co-stimulatory molecules, and enhanced antigen uptake and migratory capacities. Furthermore, Egr2-KD abolished SOCS1 expression and signal transducer and activator of transcription 5 (STAT5) activation during DC development, probably resulting in the enhancement of IL-12 expression and Th1 immunogenicity of a DC vaccine. DC-mediated cytotoxic T lymphocyte (CTL) activation and antitumor immunity were significantly enhanced by Egr2-KD, and impaired by Egr2 overexpression in antigen-pulsed DC vaccines. These data suggest that Egr2 acts as an intrinsic negative regulator of DC immunogenicity and can be an attractive molecular target for DC vaccine development.

Chemokine programming dendritic cell antigen response: part II – programming antigen presentation to T lymphocytes by partially maintaining immature dendritic cell phenotype

In a companion article to this study,(1) the successful programming of a JAWSII dendritic cell (DC) line's antigen uptake and processing was demonstrated based on pre-treatment of DCs with a specific 'cocktail' of select chemokines. Chemokine pre-treatment modulated cytokine production before and after DC maturation [by lipopolysaccharide (LPS)]. After DC maturation, it induced an antigen uptake and processing capacity at levels 36% and 82% higher than in immature DCs, respectively. Such programming proffers a potential new approach to enhance vaccine efficiency. Unfortunately, simply enhancing antigen uptake does not guarantee the desired activation and proliferation of lymphocytes, e.g. CD4(+) T cells. In this study, phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs were examined in long-term co-culture with antigen-specific CD4(+) T cells to quantify how chemokine pre-treatment may impact the adaptive immune response. When a model antigen, ovalbumin (OVA), was added after intentional LPS maturation of chemokine-treated DCs, OVA-biased CD4(+) T-cell proliferation was initiated from ~ 100% more undivided naive T cells as compared to DCs treated only with LPS. Secretion of the cytokines interferon-γ, interleukin-1β, interleukin-2 and interleukin-10 in the CD4(+) T cell : DC co-culture (with or without chemokine pre-treatment) were essentially the same. Chemokine programming of DCs with a 7 : 3 ratio of CCL3 : CCL19 followed by LPS treatment maintained partial immature phenotypes of DCs, as indicated by surface marker (CD80 and CD86) expression over time. Results here and in our companion paper suggest that chemokine programming of DCs may provide a novel immunotherapy strategy to obviate the natural endocytosis limit of DC antigen uptake, thus potentially increasing DC-based vaccine efficiency.

Chemokine programming dendritic cell antigen response: part I – select chemokine programming of antigen uptake even after maturation

Here, we report on the successful programming of dendritic cells (DCs) using selectively applied mixtures of chemokines as a novel protocol for engineering vaccine efficiency. Antigen internalization by DCs is a pivotal step in antigen uptake/presentation for bridging innate and adaptive immunity and in exogenous gene delivery used in vaccine strategies. Contrary to most approaches to improve vaccine efficiency, active enhancement of antigen internalization by DCs as a vaccine strategy has been less studied because DCs naturally down-regulate antigen internalization upon maturation. Whereas chemokines are mainly known as signal proteins that induce leucocyte chemotaxis, very little research has been carried out to identify any additional effects of chemokines on DCs following maturation. Here, immature DCs are pre-treated with select chemokines before intentional maturation using lipopolysaccharide (LPS). When pre-treated with a mixture of CCL3 and CCL19 in a 7 : 3 ratio, then matured with LPS, chemokine pre-treated DCs exhibited 36% higher antigen uptake capacity than immature DCs and 27% higher antigen-processing capacity than immature DCs treated only with LPS. Further, CCL3 : CCL19 (7 : 3) pre-treatment of DCs modulated MHC molecule expression and secretion of various cytokines of DCs. Collectively, DC programming was feasible using a specific chemokine combination and these results provide a novel strategy for enhancing DC-based vaccine efficiency. In Part II, we report on the phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs examined in long-term co-culture with antigen-specific CD4(+) T cells.

18β-Glycyrrhetinic acid from licorice root impairs dendritic cells maturation and Th1 immune responses

18β-Glycyrrhetinic acid (β-GA) is a natural triterpenoid compound derived from licorice root. β-GA has been demonstrated to exert antiviral and antitumor effects. However, the effects of the maturation and immunostimulatory functions of dendritic cells (DCs) remain to be clearly elucidated. In this study, we attempted to determine whether β-GA could influence DCs surface molecule expression, antigen uptake capacity, cytokine production and capacity to induce T-cell differentiation. The DCs used in this study were derived from murine bone marrow cells, and were used as immature or lipopolysaccharide (LPS)-stimulated mature DCs. The DCs were then assessed with regard to surface molecules expression, cytokine production, capacity to induce T-cell differentiation and proliferation. β-GA was shown to significantly suppress the expression of surface molecules CD80, CD86, major histocompatibility complex (MHC) class I and MHC class II as well as the levels of interleukin-12 production in LPS-stimulated DCs. Moreover, β-GA-treated DCs showed an impaired induction of the T helper type 1 immune response. These findings provide important understanding of the immunopharmacological functions of β-GA and have ramifications for the development of therapeutic adjuvants for the treatment of DCs-related acute and chronic diseases.

Combinatorial Signaling through TLR-2 and CD86 Augments Activation and Differentiation of Resting B Cells

B cells are an integral component in mounting humoral immune responses and they are also crucial in programming T cell mediated immunity. Usually, B cell activation is initiated by recognition of antigen through B cell receptor (BCR), followed by its processing and presentation to T cells. But very little is known about BCR independent activation of B cells. Now, there is an increasing body of evidence indicating the combinatorial effect of innate and adaptive immune components in modulating the functions of B cells. In this study, we demonstrate the activation of resting B cells (RB) by simultaneous involvement of Toll like Receptor-2 (TLR-2) and costimulatory molecule, CD86. Interestingly, these B cells exhibited significant level of activation and proliferation. Furthermore, this process of activation leads to the differentiation of RB cells, preferably into marginal zone precursors (CD19+IgDhiIgMhiCD21/35hiCD23hi) in a shorter time window and showed increased secretion of IgG isotype. These RB cells also showed enhanced antigen uptake capacity. These observations were also substantiated by microarray gene expression results, which strengthen the notion that combinatorial signaling through innate and adaptive immune components enhances B cell mediated immune response. Thus, the present study elucidates a novel BCR independent B cell activation mechanism that links TLR-2 and CD86. Hence signaling of TLRs in conjunction with costimulatory molecules will substantially help in bolstering humoral immune response, which can be extrapolated to formulate vaccination strategies for diseases involving B cell-mediated immunity.

Baicalin From Scutellaria baicalensis Impairs Th1 Polarization Through Inhibition of Dendritic Cell Maturation

Baicalin from Scutellaria baicalensis is a major flavonoid constituent found in the traditional Chinese medicinal herb Baikal skull cap. It has been widely used for the treatment of various diseases such as pneumonia, diarrhea, and hepatitis. Recent studies have demonstrated that baicalin possesses a wide range of pharmacological and biological activities, including anti-inflammatory, anti-microbial, anti-oxidant, and anti-tumor properties. Specifically, its antiinflammatory activity has been estimated in various animal models of acute and chronic inflammation; however, its effects on dendritic cells (DCs) maturation and immuno-stimulatory activities are still unknown. In this study, we attempted to determine whether baicalin could influence DC surface molecule expression, antigen uptake capacity, cytokine production, and capacity to induce T-cell differentiation. Baicalin was shown to significantly suppress the expression of surface molecules CD80, CD86, major histocompatibility complex (MHC) class I, and MHC class II as well as the levels of interleukin-12 production in lipopolysaccharide stimulated DCs. Moreover, baicalin-treated DCs showed an impaired induction of the T helper type 1 immune response and a normal cell-mediated immune response. These findings provide important understanding of the immunopharmacological functions of baicalin and have ramifications for the development of therapeutic adjuvants for the treatment of DCs-related acute and chronic diseases.

Effect of Low dose Radiation on Differentiation of Bone Marrow Cells into Dendritic Cells

Low dose radiation has been shown to be beneficial to living organisms using several biological systems, including immune and hematopoietic systems. Chronic low dose radiation was shown to stimulate immune systems, resulting in controlling the proliferation of cancer cells, maintain immune balance and induce hematopoietic hormesis. Since dendritic cells are differentiated from bone marrow cells and are key players in maintaining the balance between immune activation and tolerance, it may be important to further characterize whether low dose radiation can influence the capacity of bone marrow cells to differentiate into dendritic cells. We have shown that bone marrow cells from low dose-irradiated (γ-radiation, 0.2Gy, 15.44mGy/h) mice can differentiate into dendritic cells that have several different characteristics, such as expression of surface molecules, cytokine secretion and antigen uptake capacity, when compared to dentritic cells differentiated from the control bone marrow cells. These differences observed in the low dose radiation group can be beneficial to living organisms either by activation of immune responses to foreign antigens or tumors, or maintenance of self-tolerance. To the best of our knowledge, this is the first report showing that total-body low dose radiation can modulate the capacity of bone marrow cells to differentiate into dendritic cells.

Human proximal tubule epithelial cells modulate autologous dendritic cell function

We have previously demonstrated that human kidney proximal tubule epithelial cells (PTEC) are able to modulate autologous T and B lymphocyte responses. It is well established that dendritic cells (DC) are responsible for the initiation and direction of adaptive immune responses and that these cells occur in the renal interstitium in close apposition to PTEC under inflammatory disease settings. However, there is no information regarding the interaction of PTEC with DC in an autologous human context. Human monocytes were differentiated into monocyte-derived DC (MoDC) in the absence or presence of primary autologous activated PTEC and matured with polyinosinic:polycytidylic acid [poly(I:C)], while purified, pre-formed myeloid blood DC (CD1c(+) BDC) were cultured with autologous activated PTEC in the absence or presence of poly(I:C) stimulation. DC responses were monitored by surface antigen expression, cytokine secretion, antigen uptake capacity and allogeneic T-cell-stimulatory ability. The presence of autologous activated PTEC inhibited the differentiation of monocytes to MoDC. Furthermore, MoDC differentiated in the presence of PTEC displayed an immature surface phenotype, efficient phagocytic capacity and, upon poly(I:C) stimulation, secreted low levels of pro-inflammatory cytokine interleukin (IL)-12p70, high levels of anti-inflammatory cytokine IL-10 and induced weak Th1 responses. Similarly, pre-formed CD1c(+) BDC matured in the presence of PTEC exhibited an immature tolerogenic surface phenotype, strong endocytic and phagocytic ability and stimulated significantly attenuated T-cell proliferative responses. Our data suggest that activated PTEC regulate human autologous immunity via complex interactions with DC. The ability of PTEC to modulate autologous DC function has important implications for the dampening of pro-inflammatory immune responses within the tubulointerstitium in renal injuries. Further dissection of the mechanisms of PTEC modulation of autologous immune responses may offer targets for therapeutic intervention in renal medicine.

Lentivectors are efficient tools to manipulate the dendritic cell cytoskeleton

Dendritic cells (DC) are key cells of the innate immune system required to prime adaptive immunity. Central DC functions including antigen uptake and presentation and DC migration are critically dependent on dynamic cytoskeletal reorganisation, the regulation of which remains poorly understood. Cytoskeletal studies are complicated by the fact that DC cytoarchitecture is altered considerably by maturation stimuli, including many tools employed for biological manipulation. Lentiviral vectors, capable of transducing non-dividing cells such as DC, hold promise both for experimental and therapeutic manipulation of DC gene and protein expression but controversy remains about their effect on DC maturation. Here, we have examined the potential of lentiviral vectors as tools for gene delivery to monocyte derived human DC with preservation of immature DC cytoskeletal structure and function. We show that vesicular stomatitis virus G glycoprotein (VSVG)-pseudotyped lentivectors are most efficient at transducing immature DC and their precursor monocytes. Even at high multiplicities of infection transduced DC retained an immature cytoskeletal phenotype, with no significant alteration of migration, antigen uptake or T-cell stimulation capacities. Furthermore, lentivectors did not alter subsequent functional maturation of the DC cytoskeleton in response to lipopolysaccharide exposure. Together our data show that VSVG-psudotyped lentiviral vectors are an effective tool for gene manipulation in human DC with preservation of functional immaturity and plasticity, making them ideal for studies of the DC cytoskeleton.

CD40 Signaling Synergizes with TLR-2 in the BCR Independent Activation of Resting B Cells

Conventionally, signaling through BCR initiates sequence of events necessary for activation and differentiation of B cells. We report an alternative approach, independent of BCR, for stimulating resting B (RB) cells, by involving TLR-2 and CD40 - molecules crucial for innate and adaptive immunity. CD40 triggering of TLR-2 stimulated RB cells significantly augments their activation, proliferation and differentiation. It also substantially ameliorates the calcium flux, antigen uptake capacity and ability of B cells to activate T cells. The survival of RB cells was improved and it increases the number of cells expressing activation induced deaminase (AID), signifying class switch recombination (CSR). Further, we also observed increased activation rate and decreased threshold period required for optimum stimulation of RB cells. These results corroborate well with microarray gene expression data. This study provides novel insights into coordination between the molecules of innate and adaptive immunity in activating B cells, in a BCR independent manner. This strategy can be exploited to design vaccines to bolster B cell activation and antigen presenting efficiency, leading to faster and better immune response.

Generation of antitumor response by IL-2-transduced JAWS II dendritic cells

Antigen-loaded dendritic cells (DCs) are a promising tool for inducing a tumor-specific immune response. It seems probable that co-administration of those cells together with cytokine-transduced DCs can further increase effectiveness of the antitumor vaccine. The local production of IL-2 by genetically modified DCs may result in alteration of the unfavorable tumor environment causing immune response dysfunction. In the presented study murine DCs of an established JAWS II cell line were transduced with a retroviral vector carrying murine IL-2 gene (JAWS II/IL-2). JAWS II/IL-2 cells demonstrated slightly decreased tumor antigen (TAg) uptake capacities. However, this modification resulted in enhanced ability of the cells to migrate in vivo. The multiple injection of vaccines containing JAWS II/IL-2 cells caused MC38 tumor growth delay and prolonged mice survival. The immunological response was manifested as cytotoxic natural killer (NK) and T cell activation and tumor tissue infiltration by CD8 + and CD4 + cells, accompanied by increased IFN-γ production by spleen cells. These observations suggest that repeated peritumoral administration of IL-2-producing dendritic cells can inhibit tumor growth by intensification of CD8 + and CD4 + cells’ influx into tumor tissue and further activation of the systemic antitumor response. It can be concluded that IL-2 transduced dendritic cells may be used as a potent adjuvant in antitumor immunotherapy.