Culture Supernatant Of Dendritic Cells Research Articles

Anti-Thymocyte Globulin Treatment Augments 1,25-Dihydroxyvitamin D3 Serum Levels in Patients Undergoing Hematopoietic Stem Cell Transplantation.

Application of anti-thymocyte globulin (ATG) is a widely used strategy for the prevention of graft-versus-host disease (GvHD). As vitamin D3 serum levels are also discussed to affect hematopoietic stem cell transplantation (HSCT) outcome and GvHD development, we analysed a possible interplay between ATG treatment and serum levels of 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 in 4 HSCT cohorts with different vitamin D3 supplementation. ATG is significantly associated with higher serum level of 1,25-dihydroxyvitamin D3 around HSCT (day -2 to 7, peri-transplant), however only in patients with adequate levels of its precursor 25-hydroxyvitamin D3. ATG exposure had no impact on overall survival in patients supplemented with high dose vitamin D3, but was associated with higher risk of one-year treatment-related mortality (log rank test p=0.041) in patients with no/low vitamin D3 supplementation. However, the difference failed to reach significance applying a Cox-model regression without and with adjustment for baseline risk factors (unadjusted P=0,058, adjusted p=0,139). To shed some light on underlying mechanisms, we investigated the impact of ATG on 1,25-Dihydroxyvitamin D3 production by human dendritic cells (DCs) in vitro. ATG increased gene expression of CYP27B1, the enzyme responsible for the conversion of 25-hydroxyvitamin D3 into 1,25-dihydroxyvitamin D3, which was accompanied by higher 1,25-dihydroxyvitamin D3 levels in ATG-treated DC culture supernatants. Our data demonstrate a cooperative effect of 25-hydroxyvitamin D3 and ATG in the regulation of 1,25-dihydroxyvitamin D3 production. This finding may be of importance in the context of HSCT, where early high levels of 1,25-dihydroxyvitamin D3 levels have been shown to be predictive for lower transplant related mortality and suggest that vitamin D3 supplementation may especially be important in patients receiving ATG for GvHD prophylaxis.

Exosomes from dendritic cells with Mettl3 gene knockdown prevent immune rejection in a mouse cardiac allograft model.

We have previously demonstrated that Mettl3-silencing dendritic cells (DCs) exhibited immature properties and prolonged allograft survival in a murine heart transplantation model. Exosomes derived from donor DCs (Dex) are involved in the immune rejection of organ transplantation, and blocking Dex transfer may suppress immune rejection. Herein, this study aimed to investigate whether Mettl3 knockdown inhibits the secretion and activity of donor Dex, thereby inhibiting donor Dex-mediated immune rejection. The imDex, mDex, shCtrl-mDex, and shMettl3-mDex were obtained from the culture supernatant of DCs (immature DCs, mature DCs, shCtrl-infected mature DCs, shMettl3-infected mature DCs) derived from donor BALB/c mouse bone marrow and then co-cultured with splenic T cell lymphocyte suspension from recipient C57BL/6 mice in vitro or injected into recipient C57BL/6 mice before the cardiac transplantation. Donor shMettl3-mDex expressed lower concentration of exosomes and lower expression of Mettl3, Dex markers (ICAM-1, MHC-I, MHC-II), as well as lower ability to activate T cell immune response than shCtrl-mDex. Administration of donor shMettl3-mDex attenuated immune rejection after mouse heart transplantation and prolonged the allograft survival. In summary, Mettl3 knockdown inhibits the immune rejection of Dex in a mouse cardiac allograft model.

Allostimulatory Effects of Dendritic Cells with Characteristic Features of a Regulatory Phenotype.

IntroductionTolerogenic dendritic cells (DCs) have the potential to prolong graft survival after transplantation. Tolerogenic DCs are in general characterized by a low expression of co-stimulatory molecule and a high IL-10:IL-12 production ratio. Based on promising results with earlier used alternatively activated DCs, we aimed to generate in culture potentially tolerogenic DC by simultaneously blocking GSK3 by lithium chloride (LiCl) and stimulating TLR2 by PAM3CysSerLys4.Materials and MethodsBone marrow-derived LiClPAM3 DCs were generated by the addition of LiCl 24 hours before harvesting, and one hour later PAM3CysSerLys4. The phenotype of the DCs was assessed by determining the expression of co-stimulatory molecules in flow cytometry and cytokine production in ELISA, whereas their functional properties were tested in a mixed lymphocyte reaction. A fully MHC mismatched heterotopic heart transplant preceded by infusion of donor-derived LiClPAM3 DC was performed to assess the tolerogenic potential of LiClPAM3 DCs in vivo.ResultsLiClPAM3 DCs displayed a tolerogenic phenotype accompanied with a low expression of co-stimulatory molecules and a high IL-10:IL-12 production ratio. However, in mixed lymphocyte reaction, LiClPAM3 DCs appeared superior in T cell stimulation, and induced Th1 and Th17 differentiation. Moreover, mice pretreated with LiClPAM3 DC displayed a reduced graft survival. Analysis of LiClPAM3 DC culture supernatant revealed high levels of CXCL-1, which was also found in supernatants of co-cultures of LiClPAM3 DC and T cells. Nevertheless, we could not show a role for CXCL-1 in T cell proliferation or activation in vitro.DiscussionLiClPAM3 DCs display in vitro a tolerogenic phenotype with a high IL-10:IL-12 ratio, but appeared to be highly immunogenic, since allograft rejection was accelerated. As yet unidentified LiClPAM3 DC-derived factors, may explain the immunogenic character of LiClPAM3 DCs in vivo.

Exopolysaccharide from Trichoderma pseudokoningii promotes maturation of murine dendritic cells

Dendritic cells (DCs) are the key regulators of immune responses. In this study, the effect of an exopolysaccharide (EPS) from the culture broth of Trichoderma pseudokoningii on the phenotypic and functional maturation of murine DCs and its underlying molecular mechanisms were investigated. It showed that EPS induced the morphological changes of DCs and the enhanced expression of DCs featured surface molecules CD11c, CD86, CD80 and major histocompatibility complex II (MHC-II). Flow cytometry analysis showed that the treatment with EPS could reduce FITC-dextran uptake by DCs. Sequentially, the results of ELISA indicated that EPS could increase the production of interleukin-12p70 (IL-12p70) in culture supernatant of DCs. Immunofluorescence staining and western blot analysis further revealed that EPS significantly prompted nuclear factor (NF)-κB subunit p65 translocation, IκB-α protein degradation, and p38 mitogen-activated protein kinase (MAPK) phosphorylation. And the production of IL-12p70 was significantly decreased in condition of the inhibition of p38 or NF-κB signaling pathway. These findings suggested that EPS could induce DCs maturation through both p38 MAPK and NF-κB signaling pathways.

Functional analysis of the receptor Dectin-1 on dendritic cells from a patient with recurrent vulvovaginal candidiasis

Objective To compare the Dectin-1 signal transduction pathway and its function on dendritic cells between a female patient with recurrent vulvovaginal candidiasis (RVVC) and a healthy woman, and to explore the possible mechanism for VVC recurrence in this patient. Methods Venous blood samples were collected from a female patient with RVVC and a healthy woman. Then, monocytes were isolated from the blood samples, and were induced to differentiate into dendritic cells (DCs) in vitro. The obtained DCs were divided into three groups to be cultured alone, cocultured with Candida albicans or the combination of Candida albicans and anti-Dectin-1 antibodies for different durations. Flow cytometry was performed to determine the expression levels of CD83, CD86 and CD80 on DCs to evaluate the maturity of DCs, Western blot analysis to measure the protein expressions of Dectin-1, Syk and CARD9 in DCs, and enzyme-linked immunosorbent assay (ELISA) to determine the levels of interleukin (IL) -23, tumor necrosis factor α (TNF-α) and IL-12 in the culture supernatant of DCs. Results After co-culture with Candida albicans for 24 hours, the expressions of CD83, CD86 and CD80 were significantly inhibited on the patient-derived DCs compared with the control-derived DCs. Western blot analysis showed no significant differences in the expression of Dectin-1 between the control-and patient-derived DCs, but a decrease in the expressions of phosphorylated-Syk and CARD9 in the patient-derived DCs compared with the control-derived DCs after 2-hour coculture with Candida albicans. After co-culture with Candida albicans for 6 hours, the levels of IL-23, TNF-α and IL-12 were lower in the culture supernatant of patient-derived DCs than in that of control-derived DCs. Furthermore, the anti-Dectin antibody showed no inhibitory effects on the activation of the Syk-dependent signal transduction pathway in or the secretion of the above cytokines by the patient-derived DCs. Conclusion The Dectin-1 signal transduction pathway was abnormal in DCs from the patient with RVVC, which may decelerate the maturation of DCs, inhibit the secretion of IL-23, TNF-α and IL-12 by them, and finally result in a defect in natural mucosal immunity against Candida infection in the host. Key words: Candidiasis, vulvovaginal; Dendritic cells; Protein-tyrosine kinases; Decin-1; CARD9

House dust mite allergens mediate the activation of c‑kit in dendritic cells via Toll‑like receptor 2.

Several studies have demonstrated that the c‑kit proto‑oncogene and its ligand, stem cell factor, are important in the development of asthma. House dust mite (HDM; Dermatophagoides pteronyssinus) allergens are a major trigger in the development and exacerbation of asthma. HDM allergens can induce the activation of c‑kit in dendritic cells (DCs), leading to the development of allergic asthma. Previous studies have demonstrated that activation of Toll‑like receptor 2 (TLR2) evokes a T helper (Th)2 immune response and promotes experimental asthma. The aim of the present study was to assess whether HDM mediates the activation of c‑kit in DCs via TLR2. Monocyte‑derived DCs were generated from C57BL/6 mice, and cultured with interleukin (IL)‑4 and granulocyte‑macrophage colony‑stimulating factor. The DCs were then sensitized with HDM (10 µg/ml) for 72 h. TLR2‑specific small interfering (si)RNA was used to silence and inhibit the expression of TLR2 in the DCs. The expression levels of c‑kit and B7 (CD80/CD86) were measured, by analyzing the DC culture supernatant for the presence of IL‑6 and IL‑12. Inhibition of TLR2 using specific siRNA downregulated the expression of c‑kit in the HDM‑activated DCs. In addition, silencing of TLR2 inhibited the expression of CD80/CD86, decreased the production of IL‑6, and increased the production of IL‑12. These results indicated that TRL2 are important in the activation of c‑kit by HDM in DCs.

PD35 ‐ In vitro effects of atorvastatin on function, proliferation and cytokine production of human peripheral blood mononuclear cells

Statins, which are used as cholesterol-lowering agents, have anti-inflammatory and immune-regulating properties. Little comprehensive analysis has been made to investigate the impact of statins on human T lymphocytes function, their proliferation and production of Th1 and Th2 cytokines. We also investigated if the immunossupresive effects of statins are due to their impact on human T lymphocytes or proffesional antigen-presenting dendritic cells (DC) alone, or both. Human peripheral blood mononuclear cells (MNC) proliferation was induced with phytohemagglutinin. Immature DC were cultivated from monocytes of healthy donors. DC maturation was induced by lipopolysaccharide (LPS; 1 μg/mL). Unstimulated and LPS-stimulated DC were treated with atorvastatin (1-10 μM). Ability to induce T cell proliferation and the secretion of cytokines were performed in mixed leukocyte reaction. Atorvastatin reduced phytohemagglutinin-stimulated MNC proliferation, dose dependently. The results showed that atorvastatin, only in high concentrations, strongly inhibit allogenic lymphocytes proliferation irrespectively which stimulators are used: immature or mature dendritic cells. Low concentrations of atorvastatin even stimulated proliferation when the immature dendritic cells were used as stimulators. Atorvastatin have influence on DC differentiation and maturation by changing expression and mean fluorescence intensity of costimulatory, adhesive and maturation molecules such as HLA-DR, CD80, CD83, CD86, CD40, CD54 and CD25. Atorvastatin affects allostimulatory activity of both immature and mature MoDC but in completely oposite way, using different DC/Ly ratio, and change production of TNF-a by immature DC and IL-18 by mature DC and not affect IL-10 and IL-12 production. Atorvastatin decreased the level of IFN-g, increase the level of IL-10, and not affected the level of IL-4 in DC culture supernatants when the atorvastatin was added during maturation. If the atorvastatin was added in monocite culture, no significant change in cytokine level was observed. Our data provide strong evidence that atorvastatin can act as an immunomodulator by reducing, but in low dosage stimulating T lymphocite proliferation, inhibiting the immune response of Th1, decreasing the expression of co-stimulatory molecules, and changing DC cytokine secretion, which can help in better understanding how to take advantage of these new mechanistic insights in increased use of statins in therapeutic strategy in different immune/inflamatory disorders in future.

Eps8 vaccine exerts prophylactic antitumor effects in a murine model: A novel vaccine for breast carcinoma

Cancer vaccines are an effective way to prevent the occurrence of cancer. Epidermal growth factor receptor pathway substrate 8 (Eps8) is a novel tumor-associated antigen, which is overexpressed in the majority of tumor types. In the present study, the Eps8 protein was cloned and characterized, and its feasibility as an antitumor agent in murine breast carcinoma was investigated. The results revealed that the Eps8 protein increased the secretion of interleukin (IL)-12 in the culture supernatant of dendritic cells (DCs). The Eps8 protein‑pulsed DCs induced significant cytotoxic T lymphocyte (CTL) responses, T-cell proliferation and a higher level of interferon (IFN)-γ in the culture supernatant of the splenocytes ex vivo. Additionally, when the mice were immunized with the Eps8 vaccine, this resulted in a regression of 4T1 breast tumors and significantly prolonged survival time in the tumor‑bearing mice compared with that in the phosphate-buffered saline (PBS) control group. The Eps8 vaccine induced higher CTL responses in the splenocytes of mice vaccinated against the 4T1 cells; the ratio of CD4+/CD8+ T cells was increased in the Eps8 group; and the percentage of CD4+CD25+ FoxP3+ regulatory T (Treg) cells in the Eps8 group was significantly lower compared with that of the PBS group. The results suggested that the Eps8 vaccine was able to stimulate antitumor effects against 4T1 breast cancer cells in vitro and in vivo, and it may provide a potential immunotherapeutic agent for the treatment of breast cancer.

Superior Immunogenicity of Idiotype Fab Fragments As Compared to Entire Immunoglobulin for Active Lymphoma Immunotherapy

Abstract 1633 Introduction:The individual collection of epitopes within the variable regions of the unique immunoglobulin expressed by every mature B-cell lymphoma (idiotype, or Id) represents a tumor-specific antigen and lends itself as a target for therapeutic vaccination strategies. Immunization with tumor Id has the capacity to elicit polyclonal antibody responses as well as CD8+ and CD4+ T cells recognizing Id-derived peptides presented on class I and class II HLA molecules, respectively. Due to a perceived low immunogenicity of lymphoma-derived Id, most Id vaccines tested in clinical trials so far have been formulated as conjugates with the strongly immunogenic carrier keyhole limpet hemocyanin (KLH). In contrast, we have consistently observed high rates of humoral and cellular anti-Id immune responses in consecutive trials of active immunization with unconjugated recombinant Fab fragments of Id in indolent B-cell lymphomas (Bertinetti et al., Cancer Res. 2006; Navarrete et al., BLOOD 2011). We therefore hypothesized that Id Fab fragment might be intrinsically more immunogenic than entire Id Ig and tested this hypothesis by comparative in vitro experiments. Methods:Monocyte-derived dendritic cells (DC) where loaded with human monoclonal IgG, papain-digested Fab fragments, Fc fragments, or recombinant lymphoma-derived Fab fragments. Functional DC phenotypes were assessed by flow cytometry of crucial maturation and activation markers. IL-10 and IL-12 was measured in DC culture supernatants by ELISA. Antigen-loaded DC where subsequently used for priming of CFSE-labeled autologous peripheral blood mononuclear cells. Stimulated T cell populations were analyzed by multicolor flow cytometry. Results:Loading of DC with Fab, Fc, IgG, or mixtures of Fab and Fc fragments did not alter surface expression of CD11c, CD80, CD83, CD86, HLA-DR, PDL-1 and PDL-2 on DC. Likewise, the various antigens did not influence the cytokine release by DC during the loading or maturation process. DC loaded with isolated Fab fragments induced significantly higher proliferation of both CD4+ and CD8+ T cells than undigested IgG. The mean proliferation rate of CD4+ cells stimulated with Fab fragments was 18.5% versus 5.6% for undigested IgG stimulation (p=0.021); proliferation rates of CD8+ cells were 14.2% versus 6.2% (p=0.034). These results were reproduced for 4 different monoclonal IgGs tested on 4 different donors. The addition of Fc fragments to Fab reduced the proliferation rates of CD4+ and CD8+ cells to 10.2% and 8.6% respectively. In addition, DC loaded with undigested IgG induced a relative increase in the number of CD25high/FoxP3+ regulatory T cells compared with Fab stimulation (8.2% versus 1.4%; p<0.01). Conclusions:Isolated Fab fragments, i.e. the Id portions that contain the individual candidate antigenic epitopes of B-cell lymphomas, prime autologous T cells in vitro more efficiently than entire IgG. This finding is consistent with the high immune response rate against recombinant unconjugated Fab fragments observed in vivo in our clinical vaccination trials. Peptide sequences shared between Ig molecules that are predominantly located in the IgG Fc fragment appear to exert an inhibitory effect on T-cell priming. In accordance with our recent in vivo data in a syngeneic mouse model of Id vaccination (Warncke et al., Cancer Immunol. Immunother. 2011), this effect may be mediated by effective activation of Treg. Fab fragments therefore appear to be the more immunogenic and therefore preferable Ig antigenic format for active anti-Id immunotherapy. Furthermore, the inhibitory effects of IgG Fc offers a potential explanation for the recently reported lack of efficacy of Id vaccination in IgG-expressing follicular lymphomas in a randomized phase III trial, in which patients with IgM-expressing lymphomas, in contrast, had a significant benefit from Id vaccination in intention-to-treat analyses (Schuster et al., JCO 2011). Disclosures:No relevant conflicts of interest to declare.

Relationship between the phenotypes and functions of peripheral blood dendritic cells and the different spleen deficiency syndrome types in patients with chronic hepatitis B

To study the phenotypes and functions of dendritic cells (DCs) derived from peripheral blood monocytes of chronic hepatitis B (CHB) patients with different traditional Chinese medicine (TCM) syndrome types, and to explore the relationship between TCM syndrome type and DC functions. Sixty CHB patients were included in this study. All the CHB patients were divided into spleen deficiency and liver stagnation, spleen deficiency and dampness-heat and deficiency of both spleen and kidney groups according to TCM syndrome diagnosis standard. There were 20 cases in each group, and ten healthy people were included as normal control. The volunteer's peripheral blood was collected for monocyte separation, biochemical test and hepatitis B virus DNA loads detection. DCs were induced and isolated from peripheral blood monocytes, and then the expressions of surface markers CD80, CD86, CD1a and HLA-DR were detected by flow cytometric analysis method. Interleukin-10 (IL-10) production of the DCs was quantified by enzyme-linked immunosorbent assay. The proliferation of DCs in the CHB patients was slower than that in the healthy volunteers (P<0.05). The expressions of DC surface molecules such as CD80, CD86, and CD1a were obviously decreased in the CHB patients as compared with those in the healthy volunteers (P<0.05). More over, expressions of DC surface molecules were different among CHB patients with different TCM syndrome types. The positive expressions of CD80, CD1a, and HLA-DR in the CHB patients with spleen deficiency and liver stagnation were obviously higher than those in the CHB patients with deficiency of both spleen and kidney (P<0.05), and the CD1a expression in the CHB patients with spleen deficiency and dampness-heat was higher than that in the CHB patients with deficiency of both spleen and kidney (P<0.05). In DC culture supernatant, the IL-10 concentration of the CHB patients with deficiency of both spleen and kidney was higher than that of the CHB patients with spleen deficiency and liver stagnation (P<0.05), and the IL-10 concentrations of the CHB patients with different TCM syndrome types were higher than that of the healthy volunteers (P<0.05). During the pathogenic course of CHB, the phenotypes and functions of DCs are different in CHB patients with different TCM syndrome types. It suggests that there is a correlation between TCM syndrome type and body immunity function.

Toll-like receptor 2 activation by lipoteichoic acid induces differential production of pro-inflammatory cytokines in human odontoblasts, dental pulp fibroblasts and immature dendritic cells

Odontoblasts, dental pulp fibroblasts and immature dendritic cells (DCs) have been involved in the human dental pulp immune response to oral pathogens that invade dentine during the caries process. How they regulate the inflammatory response to Gram-positive bacteria remains nevertheless largely unknown. In this study we investigated the production of the pro-inflammatory cytokines tumour necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and interleukin-8 (CXCL8) in these three cell types upon stimulation with lipoteichoic acid (LTA), a cell wall component of Gram-positive bacteria that activates the pattern recognition molecule Toll-like receptor 2 (TLR2). We observed that TNF-α gene expression was up-regulated in all LTA-stimulated cell types. IL-1β gene expression was not or barely detectable in odontoblast-like cells and pulp fibroblasts when stimulated or not, but was expressed in immature DCs and increased upon stimulation. TNF-α and IL-1β proteins were detected in DC culture supernatants but not in odontoblast-like cell and pulp fibroblast ones. CXCL8 gene and protein were clearly expressed and increased in the three cell types upon LTA stimulation. These data indicate that LTA-dependent TLR2 activation in odontoblasts and pulp fibroblasts, in contrast to immature DCs, does not lead to significant TNF-α and IL-1β production, but that all three cell types influence the pulp inflammatory/immune response through CXCL8 synthesis and secretion.

BCG-Induced Dendritic Cell Responses and Suppression of Interleukin-5 Production from T Cells in Atopic Asthmatics

Bacille Calmette-Guérin (BCG) induces potent Th1 responses with the help of interleukin (IL)-10 and IL-12 released from dendritic cells (DCs), and suppresses Th2-associated allergic reactions. However, there are still some controversies on therapeutic effects of BCG in asthmatics. This study investigated whether BCG administration to DCs suppresses IL-5 production from T cells in atopic asthmatics. DCs derived from peripheral blood of subjects were cultured with or without BCG and Dermatophagoides farinae extract. Some DCs were co-cultured with T cells in the presence of BCG or the above culture supernatants. In the atopic asthmatics, BCG significantly increased IL-10 and IL-12 production from DCs. In the presence of D. farinae extract, BCG further increased IL-10 production. BCG-induced IL-10 production was significantly higher in the atopics (n=14) than in the non-atopics (n=9). Both BCG and the BCG-treated DCs culture supernatant significantly increased IFN-γ production from T cells. Both BCG and the supernatant from DCs+BCG+D. farinae co-cultures significantly decreased IL-5 production (all p<0.05), but the supernatant from DCs+BCG co-cultures did not. In conclusion, administration of BCG together with D. farinae extract effectively decreased IL-5 production from T cells, probably through the action of IL-10 and IL-12 released from DCs in D. farinae-sensitive asthmatics.

Neutrophil Elastase Converts Human Immature Dendritic Cells into Transforming Growth Factor-β1-Secreting Cells and Reduces Allostimulatory Ability

During microbial infection, neutrophils (polymorphonuclear leukocytes; PMNs) activate dendritic cells (DCs). However, early reports illustrated that neutrophil-derived mediators may suppress responses to mitogens. In the present study, we investigated the mechanism used by PMNs to modulate the immunostimulatory ability of DCs. Autologous syngeneic PMNs decreased T-cell proliferation induced by allogeneic DCs. Culture supernatant (CS) derived from PMNs also decreased allostimulation ability of immature DCs and increased the expression of transforming growth factor (TGF)-beta1 on DCs. A TGF-beta1 monoclonal antibody, a CD40 monoclonal antibody, or a serine protease inhibitor reversed the effect of PMN CS on DC allostimulatory ability. Furthermore, elastase reproduced the inhibitory effect of PMN CS on DC allostimulatory ability and the TGF-beta1 production. The role of elastase was confirmed by examining PMN CS from two patients with cyclic neutropenia, a disease due to mutations in the neutrophil elastase gene. These PMN CS samples had reduced elastase activity and were unable to increase DC TGF-beta1 production. Moreover, elastase and PMN CS induced IkappaBalpha degradation in DCs. We conclude that PMNs decrease DC allostimulatory ability via production of elastase leading to a switch of immature DCs into TGF-beta1-secreting cells.

The effects of Treponema pallidum on human dendritic cells.

Cell mediated immune responses play a prominent role in syphilis, which is caused by Treponema pallidum. The role of dendritic cells (DC) in the syphilitic infection is not well understood in human. In the present study, we studied interaction of T. pallidum with DC, generated from human peripheral blood mononuclear cells with GM-CSF and IL-4. After adding T. pallidum for 16 hours to immature DC at culture day 7, the change of surface antigens on DC was monitored by flow cytometry, the amount of IL-12 in culture supernatant of DC was measured by ELISA and T cell stimulatory capacity of DC was checked in mixed lymphocyte reaction (MLR). We have observed an efficient phagocytosis of T. pallidum by electron microscopy as early as 2 hours after addition of T. pallidum to DC. Interaction of DC with T. pallidum resulted in increased surface expression of CD83 which was proportionally increased according to the number of T. pallidum. Expressions of CD80, CD86 and HLA-DR on DC were slightly increased. The amount of IL-12 in the culture supernatant of DC was increased (1,099 pg/ml) after the addition of T. pallidum. T. pallidum-infected DC also displayed enhanced T cell stimulatory capacity in MLR. As seen from the above, we observed phagocytosis of T. pallidum by DC as early as 2 hours after addition of T. pallidum to DC and found that T. pallidum can stimulate DC maturation which mean that DC modulate an protective immune response during T. pallidum infection.

In vitro growth inhibition of a broad spectrum of tumor cell lines by activated human dendritic cells

Dendritic cells (DCs) are critical subsets of leukocytes providing antigen presentation for initiation of humoral and cellular immune responses. Their role as effector cells in tumor resistance, however, is less known. We report here that human DCs generated by culturing plastic-adherent peripheral blood monocytes in the presence of granulocyte-monocyte colony–stimulating factor (GM-CSF) and interleukin-4 have potent growth-inhibition activity in vitro on a wide spectrum of human tumor lines of different tissue origin. Proinflammatory stimuli lipopolysaccharide (LPS) and interferon-γ, but not tumor necrosis factor– and CD40 signaling, can further enhance DC-mediated inhibition of tumor growth. The growth inhibition requires contact between DCs and tumor cells while LPS treatment enhances the antitumor activity in DC culture supernatants. Our results suggest that in addition to their predominant role as regulatory cells, activated DCs are also potential effector cells in tumor immunity.