CpG promotes cross-presentation of dead cell-associated antigens by pre-CD8α+ dendritic cells [corrected

Cross-presentation of cell-associated Ags by dendritic cells (DC) plays an important role in immunity. DC in lymphoid tissues are short lived, being continuously replaced by precursors that proliferate and differentiate locally. Paradoxically, although TLR ligands promote immune responses and stimulate DC replenishment, they impair the cross-priming capacity of terminally differentiated splenic CD8α(+) DC, the major subset involved in cross-priming. In this study, we have investigated the cross-presentation capacity of newly generated murine DC and especially immediate precursors of CD8α(+) DC. We show that these DC do not cross-present Ag from dead cells unless stimulated by TLR ligands before Ag capture. TLR ligand CpG induced the expression of costimulatory molecules required for CD8 T cell activation but also regulated the intracellular mechanisms of cross-presentation such as Ag degradation rates without regulating Ag uptake. GM-CSF, an inflammatory cytokine associated with infections, also promoted cross-presentation acquisition by pre-CD8α(+) DC and synergized with TLR9 ligand. The concept that TLR ligands as well as inflammatory cytokines promote the acquisition of cross-presenting properties by pre-CD8α(+) DC has important implications during immune responses and when considering the use of these cells for vaccination.     

The role of tumor necrosis factor-α for interleukin-10 production by murine dendritic cells

In the present study, we examined the role of tumor necrosis factor (TNF) in interleukin (IL)-10 production by dendritic cells (DCs) using bone-marrow derived DCs from wild type (WT) and TNF-α knockout (TNF-α^−/−) mice. Toll-like receptor (TLR) stimulation induced substantial level of IL-10 production by WT DCs, but significantly low level of IL-10 production by TNF-α^−/− DCs. In contrast, no significant difference was detected in IL-12 p40 production between WT and TNF-α^−/− DCs. Addition of TNF-α during TLR stimulation recovered the impaired ability of TNF-α^−/− DCs for IL-10 production. This recovery appeared to be associated with an activation of extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, and phosphatidylinositol 3-kinase/Akt following the TNF-α addition. Blocking these kinases significantly inhibited IL-10 production by TNF-α^−/− DCs stimulated with TLR ligands plus TNF-α. Thus, TNF-α may be a key molecule to regulate the balance between anti-inflammatory versus inflammatory cytokine production in DCs.     

High frequency of immature dendritic cells and altered in situ production of interleukin-4 and tumor necrosis factor-α in lung cancer

INTRODUCTION: Antigen-presenting cells, like dendritic cells (DCs) and macrophages, play a significant role in the induction of an immune response and an imbalance in the proportion of macrophages, immature and mature DCs within the tumor could affect significantly the immune response to cancer. DCs and macrophages can differentiate from monocytes, depending on the milieu, where cytokines, like interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) induce DC differentiation and tumor necrosis factor (TNF)-alpha induce DC maturation. Thus, the aim of this work was to analyze by immunohistochemistry the presence of DCs (S100+ or CD1a+), macrophages (CD68+), IL-4 and TNF-alpha within the microenvironment of primary lung carcinomas. RESULTS: Higher frequencies of both immature DCs and macrophages were detected in the tumor-affected lung, when compared to the non-affected lung. Also, TNF-alpha-positive cells were more frequent, while IL-4-positive cells were less frequent in neoplastic tissues. This decreased frequency of mature DCs within the tumor was further confirmed by the lower frequency of CD14-CD80+ cells in cell suspensions obtained from the same lung tissues analyzed by flow cytometry. CONCLUSION: These data are discussed and interpreted as the result of an environment that does not oppose monocyte differentiation into DCs, but that could impair DC maturation, thus affecting the induction of effective immune responses against the tumor.     

Antitumor effects of human recombinant interleukin-1α and etoposide against human tumor cells: mechanism for synergismin vitro and activityin vivo

Recombinant human interleukin 1α (rh IL-1α) and etoposide (VP-16) synergize for direct growth inhibition of several human tumor cell linesin vitro. Our previous studies demonstrated that VP-16 increased the number of membrane-associated IL-1 receptors (IL-1Rs) and also enhanced the internalization of receptor-bound rh IL-1α. The purposes of this study were to test our hypothess that these events were critical to the synergy between rhIL-1α and VP-16, to determine whether rhIL-1α and VP-16 synergize to increase superoxide (SO) anion radical productionin vitro since SO anion has been implicated in the toxic effects of IL-1, and to investigate the antitumor efficacy of the combinaton against tumors in vivo. A375/C6 melanoma cells and OVCAR-3 ovarian carcinoma cells were tested with IL-1 receptor antagonist (IL-1ra) before exposure to rhIL-1α, VP-16 and rhIL-1α plus VP-16. The synergistic or antagonistic effects were assessed by MTT assay. SO production was measured by reduction of cytochrome C. Athymic female mice bearing the A375/C6 melanoma were treated by rhIL-1α, VP-16, and rhIL-1α+VP-16. The antitumor effects were evaluated by quantitating tumor growth and survival time. Pretreatment with the IL-1ra abrogated the synergistic effects of rhIL-1α and VP-16. The production of SO radical by A375/C6 cells was increased 2.5 fold by the combination of rhIL-1α and VP-16, and the addition of exogenous SOD blocked the synergy between rhIL-1α and VP-16. However, when A375/S0D15 cells which over-expressed manganese superoxide dismutase (MnSOD) after MnSOD cDNA transfecton were exposed to rhIL-1α and VP-16, in vitro antagonism was observed. In vivo studies demonstrated that the combination of rhIL-1α and VP-16 delayed tumor growth better than either agent alone, although long-term survival was not improved because of substantial toxicity. Our results suggest that the synergistic antitumor effects of IL-1α and VP-16 may be due to IL-1R modulation and increased internalization of IL-1-IL-1R complex by VP-16 treatment, as well as to a subsequent increase in SO anion radical production from the tumor cells exposed to both drugs. Thus, the combnation of IL-1α and VP-16 might prove useful for the treatment of malignant diseasein vivo, if the increased toxicity can be reduced or managed. The US Government’s right to retain a non-exclusive royalty-free license on and to any copyright is acknowledged.     

Effect of purified human interferon-α on the expression of differentiation antigens and mitogen reactivity of cultured human thymic cells

Human thymic cells were cultured in vitro either alone or with the addition of a highly purified preparation of human interferon-α. Immunofluorescence techniques using a series of monoclonal antibodies showed that 2-day cultured thymocytes express a more mature phenotype (low HTA 1, high T3 and HLA-A,B,C) than normal, uncultured thymocytes. Interferon addition to the cultures results in a strong increment in the number of HLA⁺ cells and in the total amount of HLA expressed by the cultured cells. Experiments with purified cell populations showed that the cortical, immature, thymocyte was the target cell for interferon action. Phytohemagglutinin responses—but not interleukin 2 responses—were diminished after pretreatment of thymic cells with interferon. We suggest that interferon may favor a pathway of intrathymic differentiation phenotypically characterized by a high content of Class I HLA antigens.     

Opposite effects of serotonin and interferon-α on the membrane potential and function of human natural killer cells

Summary In an earlier article, we reported that serotonin (5-hydroxytryptamine, 5-HT) inhibits the natural killer cell (NK) cytotoxicity of human whole blood in a dose-dependent manner and that natural human interferon-α (IFN-α) partially eliminates this effect. Because natural IFN-α might contain factors other than IFN, we repeated these experiments with recombinant human interferon-α (rhIFN-α) and separated blood lymphocytes enriched with NK cells and then demonstrated that IFN really is responsible for this effect. Furthermore, this investigation was carried out to clarify the mechanisms of the action of 5-HT and of rhIFN-α on NK cells. The inhibition of the cytotoxicity was pronounced when 5-HT was added at the onset of the cytotoxic assay, whereas the pretreatment of lymphocytes for 18 h only led to a slight inhibition. Moreover, rhIFN-α applied 1 h before or 1 h after the addition of 5-HT decreased the inhibitory effect of 5-HT. Flow cytometric analysis involving the use of a voltage-sensitive dye, oxonol, revealed that 5-HT depolarized, whereas rhIFN-α hyperpolarized the plasma membrane of the lymphocytes. Thus, it seems likely that the inhibitory effect of 5-HT on the cytotoxicity of peripheral human lymphocytes is due to the depolarization on the plasma membrane of the effector cells and that rhIFN-α antagonizes this ability via its hyperpolarizing activity.     

Age-associated changes in interferon-γ and interleukin-4 secretion by purified human CD4+ and CD8+ T cells

Aging is associated with a decline in immune function. Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), two important immune deviation-related cytokines, are mainly produced by type 1 and type 2 T cells, respectively. To investigate the age-associated changes in the secretion of these two cytokines, 20 elderly and 20 young subjects fulfilling the SENIEUR protocol were enrolled. The ratios of CD4+ to CD8+ T cells were not different between the two age groups. The CD4+ and CD8+ T cells were purified by a magnetic cell sorting system, and then activated by concurrent anti-CD3 and anti-CD28 stimulation. The released cytokines were determined by ELISA. Both the CD4+ and the CD8+ T cells of the elderly individuals secreted a significantly larger amount of IFN-gamma after activation. Profound IL-4 production by CD8+ T cells was observed in the older subjects compared with that of the young subjects. These data suggested that age-associated decrease in immunity may be related to an imbalance in the secretion of immune deviation cytokines. The number of IL-4-secreting CD8+ T cells (T cytotoxic 2) rose significantly in the older individuals. Our design also provided a useful way to differentiate the T cell subsets secreting the same cytokine, such as IFN-gamma-producing T helper 1 and T cytotoxic 1 cells.     

Fungicidal activity of human monocyte-derived multinucleated giant cells induced in vitro by Paracoccidioides brasiliensis antigen

Multinucleated giant cells (MGC) are characteristic cells in granulomatous disorders such as paracoccidioidomycosis (PCM) and also are formed in vitro from peripheral blood mononuclear cells by several stimuli. In this study, the authors investigated in vitro formation of MGC derived from monocytes of healthy individuals, stimulated with Paracoccidioides brasiliensis antigen (PbAg), compared with other stimuli such as IFN-gamma and supernatant of Con-A-stimulated peripheral blood mononuclear cells (CM-ConA). Besides, the fungicidal activity of monocytes and monocyte-derived MGC challenged with P. brasiliensis were compared, at a ratio of one fungus per 50 monocytes. Results demonstrated that PbAg, IFN-gamma, and CM-ConA stimuli were able to induce MGC generation, with fusion indices significantly higher than control cultures. Striking results were observed when MGC induced by PbAg and IFN-gamma presented higher fungicidal activity than monocytes, submitted to the same stimuli, showing a better capacity of these cells to kill P. brasiliensis. In summary, the results suggest that PbAg is able to induce MGC generation, and these cells presented higher fungicidal activity against P. brasiliensis than monocytes.     

Effective modulation of CD4+CD25+high regulatory T and NK cells in malignant patients by combination of interferon-α and interleukin-2

Overinduced CD4⁺CD25^+high regulatory T cells (Treg) and downregulated NK cells contribute to tumor-relevant immune tolerance and interfere with tumor immunity. In this study, we aimed to design a novel strategy with cytokine combination to correct the dysregulated Treg and NK cells in malignant patients. Initially, a total of 58 healthy individuals and 561 malignant patients were analyzed for their cellular immunity by flow cytometry. The average percentages of CD4⁺CD25^+high/lymphocyte were 1.30?±?1.19?% ( $ \bar{x} $ ?±?SD) in normal adults and 3.274?±?4.835?% in malignant patients (p?<?0.001). The ratio of CD4⁺CD25^+high to CD4⁺ was 3.58?±?3.19?% in normal adults and 6.01?±?5.89?% to 13.50?±?23.60?% in different kinds of malignancies (p?<?0.001). Of normal adults, 15.52?% had >3?% Treg and 12.07?% had <10?% NK cells. In contrast, the Treg (>3?%) and NK (<10?%) percentages were 40.82 and 34.94?% in malignant patients, respectively. One hundred and ten patients received the immunomodulation therapy with IFN-?? and/or IL-2. The overinduced Treg in 86.3?% and the reduced NK cells in 71.17?% of the patients were successfully modulated. In comparison, other lymphocyte subpopulations in most patients were much less affected by this treatment. No other treatment-relevant complications except slight pyrexia, fatigue, headache, and myalgia were observed. In conclusion, dysregulated Treg and/or NK cells were common in malignant patients. Different from any regimens ever reported, this strategy was simple and effective without severe complications and will become a basic regimen for other cancer therapies.     

Strategies for antigen choice and priming of dendritic cells influence the polarization and efficacy of antitumor T-cell responses in dendritic cell–based cancer vaccination

Dendritic cells (DCs) primed with tumor antigens (Ags) can stimulate tumor rejection. This study was aimed at evaluating the polarization of T-cell responses using various DC Ag-priming strategies for vaccination purposes. DCs cocultured with irradiated apoptotic tumor cells, DC-tumor fusions, and DCs pulsed with freeze-thaw tumor lysate Ags served as Ag-primed DCs, with EG7 tumor cells (class II negative) expressing OVA as the model Ag. DCs loaded with class I– and class II–restricted OVA synthetic peptides served as controls. Primed DCs were assessed by the in vitro activation of B3Z OVA-specific CD8 T cells and the proliferation of OVA-specific CD8 and CD4 T cells from OT-I and OT-II TCR transgenic mice, respectively. In vivo responses were measured by tumor regression following treatment with Ag-primed DCs and by CTL assays. Quantification of IL-2, IL-4, IL-5, IFN-, and TNF- by cytometric bead array (CBA) assay determined the polarization of TH1/TH2 responses, whereas H-2 K^b /SIINFEKL tetramers monitored the expansion of OVA-specific T cells. DC-EG7 hybrids stimulated both efficient class I and class II OVA responses, showing that DC-tumor hybrids are also capable of class II cross-presentation. The hybrids also induced the most potent CTLs, offered the highest protection against established EG7 tumors and also induced the highest stimulation of IFN- and TNF- production. DCs cocultured with irradiated EG7 were also effective at inducing OVA-specific responses, however with slightly reduced potency to those evoked by the hybrids. DCs loaded with lysates Ags were much less efficient at stimulating any of the OVA-specific T-cell responses, showed very little antitumor protection, and stimulated a weak TH1 response, overbalanced by an IL-5 TH2 response. The strategy of Ag-loading clearly influences the ability of DCs to polarize T cells for a TH1/TH2 response and thus determines the outcome of the elicited immune response, during various vaccination protocols.Abbreviations DC Dendritic cell - FSC Forward scatter - SSC Side scatter - TC Tumor cells This work was supported by Grant 9853 from the Leukaemia Research Fund, UK; a JRC studentship from GKT; and the Lewis Family Research Trust     

IL-6 and IFN-α from dsRNA-stimulated dendritic cells control expansion of regulatory T cells

Foxp3⁺CD4⁺ regulatory T cells (Treg) control not only autoimmunity but also the effective immune response against RNA virus infections, which produces virus-derived double-stranded RNA (dsRNA). To induce effective anti-viral immunity, it is a key issue to learn how Treg respond to dsRNA in vitro and in vivo. We here showed that synthetic dsRNA, polyI:C, caused peripheral expansion of functional Treg in a TICAM-1- and IL-6-dependent manner in vivo. PolyI:C did not expand Treg directly, but promoted the expansion of naturally occurring Treg indirectly through IL-6 produced from dendritic cells (DCs). In addition, the expansion of Treg by IL-6 was inhibited by IFN-α from polyI:C-stimulated DCs. These data suggest that the balance of IL-6 and IFN-α in the region of RNA virus infection may determine the number of peripheral Treg, which affects the effective immune responses against viruses.     

Comparison of media and serum supplementation for generation of monophosphoryl lipid A/interferon-γ–matured type I dendritic cells for immunotherapy

Background aimsEx vivo–generated monocyte-derived dendritic cells (DCs) matured with monophosphoryl lipid A (MPLA) and interferon-γ (IFN-γ) can be used as cancer immunotherapy. MPLA/IFN-γ DCs induce Th1 T cell responses and have migratory capacity. Different culture regimens have been used for generation of immunotherapeutic DCs, with varying results. In the present study, culture conditions for MPLA/IFN-γ–matured type I DCs were optimized for clinical application.MethodsDCs were generated from monocytes in the clinical grade culture media CellGro DC, AIM V or X-VIVO 15 in the absence or presence of 2% human serum (HS) and matured with the use of MPLA/IFN-γ. DC yield and DC functionality were assessed. DC functionality was determined by means of analysis of cytokines in culture supernatant, migratory capacity, expression of co-stimulatory molecules, T cell stimulatory capacity of DCs and T helper cell (Th) polarization by the DCs.ResultsDCs generated in the presence of 2% HS produced low amounts of pro-inflammatory cytokines and could not migrate irrespective of the medium used. In the absence of HS, MPLA/IFN-γ DCs generated in X-VIVO did not migrate either. MPLA/IFN-γ DCs generated in AIM V have slightly lower capacity to induce Th1 cells than do DCs generated in CellGro or X-VIVO.ConclusionsAddition of HS to different GMP culture media is detrimental for pro-inflammatory DC maturation and migration. In the absence of serum, CellGro is the most optimal medium tested for generation of migratory and Th1-inducing MPLA/IFN-γ DCs for cancer immunotherapy.     

Interferon-α and interleukin-12 gene therapy of cancer: interferon-α induces tumor-specific immune responses while interleukin-12 stimulates non-specific killing

Cytokine gene therapy is applied in clinical studies of tumors, and IFN-alpha and IL-12 are widely used for cancer immunotherapy. Using a poorly immunogenic murine colorectal cancer cell line, MC38, we compared antitumor effects of IFN-alpha and IL-12. Transduced MC38 cell lines expressing IFN-alpha or IL-12 (MC38-IFNalpha or MC38-IL12, respectively) were established using retroviral vectors. Transduction of IFN-alpha or IL-12 gene to MC38 cells significantly reduced tumorigenicity in immunocompetent mice. When tumor-free mice initially injected with MC38-IFNalpha or MC38-IL12 cells were reinjected contralaterally with wild-type MC38 cells (MC38-WT) after 35 days, 7 of 12 or 2 of 12 mice rejected MC38-WT cells, respectively. In therapy-model mice with established tumor derived from MC38-WT cells, inoculation of gene-transduced cells significantly suppressed growth of the tumor in MC38-IFNalpha-inoculated groups, but not in the IL-12-inoculated group. Immunohistologic and flow cytometric analyses showed marked infiltration of CD8(+) cells in wild-type tumors of mice inoculated with IFN-alpha-expressing cells. Leukocyte-depletion experiments implicated CD8(+) T cells in tumor rejection induced by IFN-alpha-transduction; both CD8(+) T cells and natural killer cells were implicated in the more modest antitumor effect from IL-12 expression. To investigate induction of tumor-specific immune responses, we stimulated splenocytes from tumor-free mice twice in vitro with genetically modified MC38 cells. In vitro stimulations with MC38-IFNalpha cells induced definite MC38-specific lysis, but not stimulations with MC38-IL-12 cells. Injecting combination of MC38-IFNalpha and MC38-IL-12 cells caused an additive antitumor effect in the therapy model. These data suggested that IFN-alpha induces cytotoxic T lymphocytes and elicits long-lasting tumor-specific immunity, whereas IL-12 seems to stimulate non-specific killing. With additional refinements, combined IFN-alpha and IL-12 gene therapy might warrant clinical trials.     

Tumor cytotoxicity of human monocyte membrane-bound interleukin-1α induced by synergistic actions of interferon-γ and synthetic acyltripeptide,FK-565

Summary Human blood monocytes were isolated by counter-flow centrifugal elutriation from healthy donors and these noncytotoxic monocytes were rendered tumoricidal to allogeneic melanoma (A375) cells by activation with a synthetic acyltripeptide (FK-565), as assessed by measuring release of [¹²⁵I]iododeoxyuridine in 72 h. When monocytes were treated with FK-565 for 16 h, and then fixed with paraformaldehyde, they showed cytotoxicity to A375 melanoma cells. The fixed-monocyte-mediated cytotoxicity to A375 cells was induced by the synergistic actions of FK-565 and recombinant interferon- (rIFN-), but not other cytokines [rIFN-A, rIFN-, tumor necrosis factor (TNF), interleukin (IL)-2, -3 and -6]. For synergistic activation of monocytes with induction of a membrane-associated antitumor monokine, the monocytes had to be incubated first with rIFN- and then with FK-565. FK-565 also acted synergistically with rIFN- to stimulate monocytes to produce membrane-associated IL-1 activity, which induced C3H/HeJ thymocyte blastogenesis in response to phytohemagglutinin P. The tumoricidal and thymocytestimulating activities of the fixed monocytes were almost completely inhibited by a specific anti-(IL-1) antiserum, but not by a specific anti-(IL-1) antiserum or monoclonal anti-TNF antibody. These results suggest that membrane-associated IL-1 of human blood monocytes can be induced by two activation signals (rIFN- then FK-565) at their suboptimal concentrations.Abbreviations IL interleukin - IFN interferon - TNF tumor necrosis factor     

Uncarinic acid C plus IFN-γ generates monocyte-derived dendritic cells and induces a potent Th1 polarization with capacity to migrate

Uncarinic acid C (URC) is triterpene isolated from Uncaria rhynchophylla and modulates human DC function in a fashion that favors Th1 cell polarization depending on TLR4 signaling. The induction of dendritic cells (DC) is critical for the induction of Ag-specific T lymphocyte responses and may be essential for the development of human vaccines relying on T cell immunity. Monocyte-derived DC used as adjuvant cells in cancer immunotherapy and have shown promising results. We studied the effect of interferon’s (IFN-α and IFN-γ) and TNF-α on phenotypic and functional maturation, and cytokine production of URC-primed DC in vitro. Human monocytes were exposed to either URC alone, or in combination with TNF-α, IFN-α or IFN-γ, and thereafter co-cultured with naïve T cells. We found that the expression levels of CD1a, CD83 and HLA-DR on URC-primed DC were influenced by IFN-γ and IFN-γ augmented the T cell stimulatory capacity in allo MLR to URC-primed DC. Moreover, the production of IL-12p70 by URC-primed DC was enhanced by IFN-γ. IL-12p70 production by URC-primed DC alone was influenced following treatment with anti-TLR4 mAb, but not DC differentiated with URC plus IFN-γ. URC plus IFN-γ-primed DC induced a substantial increase in the secretion of IFN-γ by T cells, which is dependent on IL-12 secretion. DC maturated with URC plus IFN-γ had an intermediate migratory capacity towards CCL19 and CCL21. In addition, the expression levels of CCR7 on URC-primed DC were enhanced by IFN-γ. In contrast, surface molecule up-regulation and function of URC-primed DC were slightly enhanced by TNF-α, and IFN-α. These results suggest that the enhancement of Th1 cells polarization to URC-primed DC induced by IFN-γ depends on the activation of IL-12p70 and independent on TLR4. DC differentiated with URC in combination with IFN-γ might be used on DC-based vaccine for cancer immunotherapy.     

HIV delays IFN-α production from human plasmacytoid dendritic cells and is associated with SYK phosphorylation

Plasmacytoid dendritic cells (pDC) are the major producers of type I interferons (IFNs) in humans and rapidly produce IFN-α in response to virus exposure. Although HIV infection is associated with pDC activation, it is unclear why the innate immune response is unable to effectively control viral replication. We systematically compared the effect of HIV, Influenza, Sendai, and HSV-2 at similar target cell multiplicity of infection (M.O.I.) on human pDC function. We found that Influenza, Sendai, HSV-2 and imiquimod are able to rapidly induce IFN-α production within 4 hours to maximal levels, whereas HIV had a delayed induction that was maximal only after 24 hours. In addition, maximal IFN-α induction by HIV was at least 10 fold less than that of the other viruses in the panel. HIV also induced less TNF-α and MIP-1β but similar levels of IP-10 compared to other viruses, which was also mirrored by delayed upregulation of pDC activation markers CD83 and CD86. BDCA-2 has been identified as an inhibitory receptor on pDC, signaling through a pathway that involves SYK phosphorylation. We find that compared to Influenza, HIV induces the activation of the SYK pathway. Thus, HIV delays pDC IFN-α production and pDC activation via SYK phosphorylation, allowing establishment of viral populations.     

Automated Good Manufacturing Practice–compliant generation of human monocyte-derived dendritic cells from a complete apheresis product using a hollow-fiber bioreactor system overcomes a major hurdle in the manufacture of dendritic cells for cancer vaccines

BackgroundAlthough dendritic cell (DC)–based cancer vaccines represent a promising treatment strategy, its exploration in the clinic is hampered due to the need for Good Manufacturing Practice (GMP) facilities and associated trained staff for the generation of large numbers of DCs. The Quantum bioreactor system offered by Terumo BCT represents a hollow-fiber platform integrating GMP-compliant manufacturing steps in a closed system for automated cultivation of cellular products. In the respective established protocols, the hollow fibers are coated with fibronectin and trypsin is used to harvest the final cell product, which in the case of DCs allows processing of only one tenth of an apheresis product.Materials and ResultsWe successfully developed a new protocol that circumvents the need for fibronectin coating and trypsin digestion, and makes the Quantum bioreactor system now suitable for generating large numbers of mature human monocyte-derived DCs (Mo-DCs) by processing a complete apheresis product at once. To achieve that, it needed a step-by-step optimization of DC-differentiation, e.g., the varying of media exchange rates and cytokine concentration until the total yield (% of input CD14⁺ monocytes), as well as the phenotype and functionality of mature Mo-DCs, became equivalent to those generated by our established standard production of Mo-DCs in cell culture bags.ConclusionsBy using this new protocol for the Food and Drug Administration–approved Quantum system, it is now possible for the first time to process one complete apheresis to automatically generate large numbers of human Mo-DCs, making it much more feasible to exploit the potential of individualized DC-based immunotherapy.