Comparison of two different protocols for the induction of maturation of human dendritic cells in vitro

Daphnoretin modulates differentiation and maturation of human dendritic cells through down-regulation of c-Jun N-terminal kinase

Daphnoretin, an active constituent of Wikstroemia indica C.A. Meys, has been shown possessing anti-cancer activity. In this study, we examined the effect of daphnoretin on differentiation and maturation of human myeloid dendritic cells (DCs). After treatment with daphnoretin (0, 1.1, 3.3, 10 and 30μM) to initiate monocytes, the recovery rate of DCs was reduced in a dose-dependent manner. The mature DCs differentiated in the presence of daphnoretin had fewer and shorter dendrites. Daphnoretin modulated DCs differentiation and maturation in terms of lower expression of CD1a, CD40, CD83, DC-SIGN, and HLA-DR. Daphnoretin inhibited the allostimulatory activity of DCs on proliferation of naive CD4⁺CD45⁺RA⁺ T cell. On the mitogen-activated protein kinase, daphnoretin down-regulated the lipopolysaccharide-augmented expression of phosphorylated c-Jun N-terminal kinase (pJNK), but not p38 and extracellular signal-regulated kinase 1/2 (ERK1/2). Activation of JNK by anisomycin reversed the effect of daphnoretin on daphnoretin-inhibited pJNK expression and dendrite formation of DCs. In disease model related to maturation of DCs, daphnoretin suppressed the acute rejection of skin allografts in mice. Our results suggest that daphnoretin modulated differentiation and maturation of DCs toward a state of atypical maturation with impaired allostimulatory function and this effect may go through down-regulation of phosphorylated JNK.

Mesenchymal stem cells from periapical lesions modulate differentiation and functional properties of monocyte-derived dendritic cells

Immunoregulatory mechanisms within periapical lesions (PLs) are as of yet unexplored. Considering the crucial role of DCs in controlling the immune response within PLs, the immunomodulatory properties of mesenchymal stem cells (MSCs), and the colocalization of MSCs and DCs in situ, we wondered whether MSCs from PLs modulate the development and functions of DCs. Using a model of monocyte-derived DCs, we showed that PL-MSCs inhibited differentiation of DCs via soluble factors, of which IL-6 had a minor effect, but did not impair their subsequent maturation induced by pro-inflammatory cytokines. However, upon maturation such DCs favored the production of Th2/Th17 cytokines by allogenic CD4(+) lymphocytes in coculture, compared with mature DCs differentiated without PL-MSCs. PL-MSC-differentiated DCs, cultivated with pro-inflammatory cytokines and PL-MSCs, although phenotypically mature, exhibited poor allostimulatory activity, induced anergy, Th2 polarization, differentiation of suppressive CD4(+) CD25(high) CD39(+) Treg-cell subsets via IDO-1-, ILT-3-, and ILT-4-dependent mechanisms, and increased production of TGF-β in the coculture. In contrast, DCs cultivated with PL-MSCs only during maturation stimulated proliferation and Th1 polarization of CD4(+) T cells in an IL-12-independent manner. In conclusion, PL-MSCs significantly modulate the development and functions of DCs, depending on the phase of DCs development during which the interaction occurs.

The response of human dendritic cells to co-ligation of pattern-recognition receptors

Dendritic cells (DCs) are key antigen-presenting cells that express a wide variety of pattern-recognition receptors (PRRs). Triggering of a single PRR, especially Toll-like receptors (TLRs) and C-type lectins, induces maturation of DCs, but cooperativity between multiple PRRs is needed in order to achieve an effective immune response. In this review, we summarize the published data related to the effect of individual and joint PRR agonists on DCs and Langerhans-like cells derived from monocytes (MoDCs and MoLCs, respectively). Our results demonstrate that MoDCs co-stimulated with TLR3/TLR7 and TLR3/Dectin-1 ligands induced superior T helper (Th)1 and Th17 immune responses, compared to effects of single agonists. The opposite outcome was observed after co-ligation of TLR3 and Langerin on MoLCs. These findings may be relevant to improve strategy for tumor immunotherapy.

Dose-dependent response of dendritic cells to 7-thia-8-oxo-guanosine and its modulation by polyinosinic:polycytidylic acid

Targeting the endosomal Toll-like receptors (TLRs) by specific agonists seems to be a promising tool for stimulation of the immunogenicity of dendritic cells (DCs). Since the functional outcome upon the engagement of TLRs may be different, the aim of our study was to examine if and how different concentrations of 7-thia-8-oxo-guanosine (7-TOG), a selective TLR7 agonist, influence differentiation, maturation and functions of human monocyte-derived DCs (MoDCs) and if its effects on MoDCs could be modulated by co-ligation of TLR3. Immature MoDCs were treated with different concentrations of 7-TOG (25, 100 and 250 μmol/L) alone, or together with polyinosinic:polycytidylic acid, Poly (I:C) (10 ng/mL), a selective TLR3 agonist, for an additional 48 h. We showed that the highest concentration of 7-TOG stimulated the differentiation, maturation and allostimulatory capability of MoDCs. These changes were accompanied by an increased production of interleukin 12 (IL-12) and induction of T helper (Th)1 and Th17 immune responses. Both Th responses were significantly augmented by additional stimulation of MoDCs with Poly (I:C). The treatment of MoDCs with the intermediate concentration of 7-TOG resulted in the up-regulation of co-stimulatory molecule (CD86) and increased production of IL-1β and IL-6 by MoDCs, followed by the stimulation of the Th17 immune response. The lowest concentration of 7-TOG down-regulated the expression of CD40 on MoDCs and potentiated the Th2 immune response. The Th2 response was not significantly modulated by additional treatment of MoDCs with Poly (I:C), but this combination of TLR3/TLR7 agonists also stimulated both Th1 and Th17 responses. In conclusion, our results show that 7-TOG influences the phenotype and functions of MoDCs in a dose-dependent manner and suggests that fine-tuned signaling through TLR7 may be modified by the engagement of TLR3, resulting in a different outcome of immune response.

Phosphatidylinositol-3-kinase activity during in vitro dendritic cell generation determines suppressive or stimulatory capacity

Modulating PI3K at different stages of dendritic cells (DC) generation could be a novel means to balance the generation of immunosuppressive versus immunostimulatory DC. We show that PI3K inhibition during mouse DC generation in vitro results in cells that are potently immunosuppressive and characteristic of CD8alpha- CD11c+ CD11b+ DC. These DC exhibited low surface class I and class II MHC, CD40, and CD86 and did not produce TNF-alpha. In allogeneic MLR, these DC were suppressive. Although in these mixed cultures, there was no increase in the frequency of CD4+ CD25+ Foxp3+ cells, the Foxp3 content on a per cell basis was significantly increased. Sustained TLR9 signaling in the presence of PI3K inhibition during DC generation overrode the cells' suppressive phenotype.

Monocyte-derived DC maturation strategies and related pathways: a transcriptional view

Ex vivo production of highly stimulator mature dendritic cells (DCs) for cellular therapy has been used to treat different pathological conditions with the aim of inducing a specific immune response. In the last decade, several protocols have been developed to mature monocyte-derived DCs: each one has led to the generation of DCs showing different phenotypes and stimulatory abilities, but it is not yet known which one is the best for inducing effective immune responses. We grouped several different maturation protocols according to the downstream pathways they activated and reviewed the shared features at a transcriptomic level to reveal the potential of DCs matured by each protocol to develop Th-polarized immune responses.

Differentiation and function of human monocyte-derived dendritic cells under the influence of leflunomide

Leflunomide is an immunosuppressive drug effective in experimental models of transplantation and autoimmune diseases and in the treatment of active rheumatoid arthritis (RA). Having in mind that it has been shown that some other immunosuppressive drugs (glucocorticoids, mycophenolate mofetil, sirolimus etc.) impair dendritic cell (DC) phenotype and function, we investigated the effect of A77 1726, an active metabolite of leflunomide, on the differentiation and function of human monocyte-derived dendritic cells (MDDC) in vitro. Immature MDDC were generated by cultivating monocytes in medium supplemented with GM-CSF and IL-4. To induce maturation, immature MDDC were cultured for 2 additional days with LPS. A77 1726 (100 ?M) was added at the beginning of cultivation. Flow cytometric analysis showed that MDDC differentiated in the presence of A77 1726 exhibited an altered phenotype, with a down-regulated surface expression of CD80, CD86, CD54 and CD40 molecules. Furthermore, the continuous presence of A77 1726 during differentiation and maturation prevented successful maturation, judging by the decreased expression of maturation marker CD83, costimulatory and adhesive molecules on A77 1726-treated mature MDDC. In addition, A77 1726-pretreated MDDC exhibited a poor stimulatory capacity of the allogeneic T cells and a low production of IL-10 and IL-18. These data suggest that leflunomide impairs the differentiation, maturation and function of human MDDC in vitro, which is an additional mechanism of its immunosuppressive effect.

Zoledronic acid, an aminobisphosphonate, modulates differentiation and maturation of human dendritic cells

Zoledronic acid (ZOL), an effective nitrogen-containing bisphosphonate against excessive bone loss, has been shown affecting the function of cells of both innate and acquired immunity. In this study, we tested the effect of ZOL on differentiation and maturation of human myeloid dendritic cells (DC). When ZOL (1.1 to 10 microM) was added to the culture of starting monocytes, but not to immature DC, the recovery rate of DC was markedly reduced in a concentration-dependent manner. The mature DC differentiated in the presence of ZOL had fewer and shorter cell projections. ZOL treatment affected DC differentiation and maturation in terms of lower expression of CD1a, CD11c, CD83, CD86, DC-SIGN, HLA-DR, and, in contrast, higher expression of CD80. IL-10 production by DC was inhibited by ZOL treatment whereas IL-12p70 secretion remained unchanged. Interestingly, ZOL augmented the allostimulatory activity of DC on naive CD4(++)CD45(+)RA(++) T cells in terms of their proliferation and interferon-gamma production. Addition of geranylgeraniol abrogated the effect of ZOL on DC differentiation and prenylation of Rap1A. It suggests that ZOL redirects DC differentiation toward a state of atypical maturation with allostimulatory function and this effect may go through prevention of Rap1A prenylation.

A novel approach to induce human DCs from monocytes by triggering 4-1BBL reverse signaling

Dendritic cells (DCs) are responsible for the initiation of immune responses. Our study demonstrates a new pathway for generating a large quantity of stimulatory monocyte-derived DCs (Mo-DCs) from human monocytes using anti-4-1BB ligand (4-1BBL) mAb to trigger reverse signaling. The anti-4-1BBL-driven Mo-DCs (DCs(alpha-4-1BBL)) not only express higher levels of CD86, CD83 and HLA-DR, when compared with the Mo-DCs matured by tumor necrosis factor alpha, but also exhibit a unique phenotype that expresses lower levels of PD-L1. High levels of GM-CSF, M-CSF and Flt3 ligand (FL) were found in the anti-4-1BBL-differentiation culture. Neutralizing M-CSF, GM-CSF and FL inhibited Mo-DC proliferation stimulated by anti-4-1BBL mAb, suggesting that M-CSF, GM-CSF and FL are involved in cell proliferation stimulated by anti-4-1BBL. Further analysis of the DCs(alpha-4-1BBL) showed increased secretion of T(h)1-type cytokines IL-12 and IFN-gamma and decreased secretion of IL-10. DCs(alpha-4-1BBL) induced much stronger proliferative responses in the mixed lymphocyte reaction assay when compared with DCs derived by GM-CSF. Moreover, DCs(alpha-4-1BBL) preferentially induced T(h)1 responses. We have further demonstrated that anti-4-1BBL antibody stimulated nuclear translocation of NF-kappaB from the cytoplasm in monocytes, suggesting that reverse signaling by 4-1BBL is likely responsible for mediating DC differentiation. Collectively, we have found that reverse signaling of 4-1BBL promotes the differentiation of potent T(h)1-inducing DCs from human monocytes.

Effect of pentoxifylline on differentiation and maturation of human monocyte-derived dendritic cells in vitro

Pentoxifylline (PTX) is a drug used for the treatment of vascular disorders, but it also has a positive therapeutic effect in experimental models of some autoimmune diseases. In this work, we studied the effect of PTX on human monocyte-derived dendritic cells (MDDCs). Immature MDDCs were generated in vitro from monocytes in the presence of recombinant human granulocyte macrophage-colony stimulating factor (rhGM-CSF) and recombinant human interleukin-4 (rhIL-4), while mature MDDCs were obtained by cultivation of immature MDDCs with lipopolysaccharide (LPS). PTX (200 micro g/ml) was added at the beginning of cell cultivation. We found that PTX significantly impaired differentiation and function of immature MDDCs, as judged by the reduced allostimulatory activity of these cells on allogeneic T cells and down-regulation of costimulatory and adhesion molecules, such as CD86, CD40 and CD54. The maturation of MDDCs in the presence of PTX and LPS was characterized by the decreased expression of maturation marker CD83 and costimulatory molecule CD86, as well as lower stimulation of alloreactive T cells compared to the control MDDCs cultivated with LPS alone. PTX-treated MDDCs which were induced to mature with LPS produced lower levels of TNF-alpha, IL-12 and IL-18 and higher levels of IL-10 than corresponding control MDDCs. PTX did not significantly alter endocytosis of dextran by both immature and mature MDDCs. Cumulatively, our results show for the first time that PTX might impair differentiation, maturation and function of human MDDCs in vitro, suggesting an additional mechanism of its immunomodulatory activity.

Platonin modulates differentiation and maturation of human monocyte-derived dendritic cells

Platonin is a photosensitizer with NF-kappaB inhibitory activity that activates macrophages and suppresses lymphocyte response. In this study, we tested the effect of platonin on differentiation and maturation of human myeloid dendritic cells (DC) from CD14+ monocytes. Triggering of DC differentiation by GM-CSF and IL-4 resulted in typical immature DCs that were further stimulated to maturation by combination of cytokines. When platonin (2 to 50 ng/mL) was added to the culture, the resulting DCs had thicker and blunter protruding projections, lower CD83 expression, greater CD80 expression, and less stimulatory activity on allogeneic naive CD4+CD45RA+ T cells in terms of their proliferation and interferon-gamma production. This suggests that platonin redirects DC differentiation toward an intermediate stage of maturation, whereby the DCs have uniquely enhanced expression of CD80 which may confer some degree of immune tolerance.