Tolerogenic dendritic cells generated with dexamethasone and vitamin D3 regulate rheumatoid arthritis CD4+ T cells partly via transforming growth factor-ß1.

Tolerogenic dendritic cells (tolDC) are a new immunotherapeutic tool for the treatment of rheumatoid arthritis (RA) and other autoimmune disorders. We have established a method to generate stable tolDC by pharmacological modulation of human monocyte-derived DC. These tolDC exert potent pro-tolerogenic actions on CD4+ T cells. Lack of interleukin (IL)-12p70 production is a key immunoregulatory attribute of tolDC but does not explain their action fully. Here we show that tolDC express transforming growth factor (TGF)-ß1 at both mRNA and protein levels, and that expression of this immunoregulatory cytokine is significantly higher in tolDC than in mature monocyte-derived DC. By inhibiting TGF-ß1 signalling we demonstrate that tolDC regulate CD4+ T cell responses in a manner that is at least partly dependent upon this cytokine. Crucially, we also show that while there is no significant difference in expression of TGF-ßRII on CD4+ T cells from RA patients and healthy controls, RA patient CD4+ T cells are measurably less responsive to TGF-ß1 than healthy control CD4+ T cells [reduced TGF-ß-induced mothers against decapentaplegic homologue (Smad)2/3 phosphorylation, forkhead box protein 3 (FoxP3) expression and suppression of (IFN)-γ secretion]. However, CD4+ T cells from RA patients can, nonetheless, be regulated efficiently by tolDC in a TGF-ß1-dependent manner. This work is important for the design and development of future studies investigating the potential use of tolDC as a novel immunotherapy for the treatment of RA.

Autologous tolerogenic dendritic cells for rheumatoid and inflammatory arthritis.

OBJECTIVES: To assess the safety of intra-articular (IA) autologous tolerogenic dendritic cells (tolDC) in patients with inflammatory arthritis and an inflamed knee; to assess the feasibility and acceptability of the approach and to assess potential effects on local and systemic disease activities. METHODS: An unblinded, randomised, controlled, dose escalation Phase I trial. TolDC were differentiated from CD14+ monocytes and loaded with autologous synovial fluid as a source of autoantigens. Cohorts of three participants received 1×106, 3×106 or 10×106 tolDC arthroscopically following saline irrigation of an inflamed (target) knee. Control participants received saline irrigation only. Primary outcome was flare of disease in the target knee within 5 days of treatment. Feasibility was assessed by successful tolDC manufacture and acceptability via patient questionnaire. Potential effects on disease activity were assessed by arthroscopic synovitis score, disease activity score (DAS)28 and Health Assessment Questionnaire (HAQ). Immunomodulatory effects were sought in peripheral blood. RESULTS: There were no target knee flares within 5 days of treatment. At day 14, arthroscopic synovitis was present in all participants except for one who received 10×106 tolDC; a further participant in this cohort declined day 14 arthroscopy because symptoms had remitted; both remained stable throughout 91 days of observation. There were no trends in DAS28 or HAQ score or consistent immunomodulatory effects in peripheral blood. 9 of 10 manufactured products met quality control release criteria; acceptability of the protocol by participants was high. CONCLUSION: IA tolDC therapy appears safe, feasible and acceptable. Knee symptoms stabilised in two patients who received 10×106 tolDC but no systemic clinical or immunomodulatory effects were detectable. TRIAL REGISTRATION NUMBER: NCT01352858.

Synovial CD4+ T-cell-derived GM-CSF supports the differentiation of an inflammatory dendritic cell population in rheumatoid arthritis.

OBJECTIVE: A population of synovial inflammatory dendritic cells (infDCs) has recently been identified in rheumatoid arthritis (RA) and is thought to be monocyte-derived. Here, we investigated the role and source of granulocyte macrophage-colony-stimulating factor (GM-CSF) in the differentiation of synovial infDC in RA. METHODS: Production of GM-CSF by peripheral blood (PB) and synovial fluid (SF) CD4+ T cells was assessed by ELISA and flow cytometry. In vitro CD4+ T-cell polarisation experiments were performed with T-cell activating CD2/CD3/CD28-coated beads in the absence or presence of pro-Th1 or pro-Th17 cytokines. CD1c+ DC and CD16+ macrophage subsets were flow-sorted and analysed morphologically and functionally (T-cell stimulatory/polarising capacity). RESULTS: RA-SF CD4+ T cells produced abundant GM-CSF upon stimulation and significantly more than RA-SF mononuclear cells depleted of CD4+ T cells. GM-CSF-producing T cells were significantly increased in RA-SF compared with non-RA inflammatory arthritis SF, active RA PB and healthy donor PB. GM-CSF-producing CD4+ T cells were expanded by Th1-promoting but not Th17-promoting conditions. Following coculture with RA-SF CD4+ T cells, but not healthy donor PB CD4+ T cells, a subpopulation of monocytes differentiated into CD1c+ infDC; a process dependent on GM-CSF. These infDC displayed potent alloproliferative capacity and enhanced GM-CSF, interleukin-17 and interferon-γ production by CD4+ T cells. InfDC with an identical phenotype to in vitro generated cells were significantly enriched in RA-SF compared with non-RA-SF/tissue/PB. CONCLUSIONS: We demonstrate a therapeutically tractable feedback loop of GM-CSF secreted by RA synovial CD4+ T cells promoting the differentiation of infDC with potent capacity to induce GM-CSF-producing CD4+ T cells.

Tolerogenic dendritic cell therapy for rheumatoid arthritis: where are we now?

Dendritic cells with tolerogenic function (tolDC) have become a promising immunotherapeutic tool for reinstating immune tolerance in rheumatoid arthritis (RA) and other autoimmune diseases. The concept underpinning tolDC therapy is that it specifically targets the pathogenic autoimmune response while leaving protective immunity intact. Findings from human in-vitro and mouse in-vivo studies have been translated into the development of clinical grade tolDC for the treatment of autoimmune disorders. Recently, two tolDC trials in RA and type I diabetes have been carried out and other trials are in progress or are imminent. In this review, we provide an update on tolDC therapy, in particular in relation to the treatment of RA, and discuss the challenges and the future perspectives of this new experimental immunotherapy.

Raised interleukin-17 is immunolocalised to neutrophils in cystic fibrosis lung disease.

Interleukin (IL)-17 is pivotal in orchestrating the activity of neutrophils. Neutrophilic inflammation is the dominant pathology in cystic fibrosis (CF) lung disease. We investigated IL-17 protein expression in the lower airway in CF, its cellular immunolocalisation and the effects of IL-17 on CF primary bronchial epithelial cells. Immunohistochemistry was performed on explanted CF lungs and compared with the non-suppurative condition pulmonary hypertension (PH). Airway lavages and epithelial cultures were generated from explanted CF lungs. Immunoreactivity for IL-17 was significantly increased in the lower airway epithelium in CF (median 14.1%) compared with PH (2.95%, p=0.0001). The number of cells staining positive for IL-17 in the lower airway mucosa was also increased (64 cells·mm(-1) compared with 9 cells·mm(-1) basement membrane, p=0.0005) and included both neutrophils in addition to mononuclear cells. IL-17 was detectable in airway lavages from explanted CF lungs. Treatment of epithelial cultures with IL-17 increased production of IL-8, IL-6 and granulocyte macrophage colony-stimulating factor. In conclusion, immunoreactive IL-17 is raised in the lower airway of people with CF and localises to both neutrophils and mononuclear cells. IL-17 increases production of pro-neutrophilic mediators by CF epithelial cells, suggesting potential for a positive feedback element in airway inflammation.

Bronchial epithelial cells cultured from clinically stable lung allograft patients promote the development of macrophages from monocytes rather than dendritic cells.

BACKGROUND: It is understood that chronic allograft failure occurs as a result of alloimmune and non-alloimmune injury. Dendritic cells (DC) are thought to be crucial in regulating (allo)immune airway damage and interactions with epithelial cells are likely. Studies in human lung transplantation are limited, however, and the available literature on DC is inconsistent. This study focused on the ex vivo influence of primary bronchial epithelial cells derived from lung allografts on DC differentiation. METHODS: Epithelial cell conditioned media (ECCM) were added to monocytes differentiating into DC under the influence of interleukin-4 and granulocyte macrophage-colony stimulating factor. The resultant cells were compared with DC cultured without ECCM and with monocyte-derived macrophages. Expression of typical DC (eg, CD1a) and macrophage (eg, CD14) markers was assessed by flow cytometry. Phenotypical assessments were complemented by functional studies of mannose receptor-mediated phagocytosis (FITC-dextran uptake) and antigen-presenting capability (mixed lymphocyte reactions). RESULTS: Cells exposed to ECCM expressed significantly lower levels of CD1a than unexposed DC. CD14 expression and phagocytic function were increased. ECCM cultured cells also expressed lower levels of T cell co-stimulatory molecules, secreted an anti-inflammatory cytokine profile and had significantly reduced antigen-presenting capability. CONCLUSION: Using phenotypic and functional approaches, this study has shown that ECCM from lung allografts drives the production of macrophage-like cells from monocytes rather than DC. The data suggest that epithelial cells may restrain airway DC and potential alloimmunity. It is unclear whether the observed effect is specifically seen in lung transplant recipients or is a general property of bronchial epithelial cells. This may reflect a homeostatic inter-relationship between airway epithelial and DC populations relevant both to lung allografts and the lung more generally.

How to deal with polarized Th2 cells: exploring the Achilles' heel.

The central effector cells in the pathogenesis of atopic allergic diseases are type 2 T helper (Th2) cells, which display an aberrant cytokine profile dominated by type 2 cytokines. Initial reports from mouse studies indicated that established and committed Th2 cells are stable and unsusceptible to modulation. However, there is a growing awareness that in humans, established effector Th2 cells are more flexible and can be reverted to predominant Th1 phenotypes. In fact, the Th1-driving cytokine interleukin (IL)-12 is the crucial factor in this respect. IL-12 is mainly produced by dendritic cells (DC), which can be primed for high or low IL-12 production, depending on inflammatory and/or microbial signals they encounter during their residence in the peripheral tissues. Accordingly, both the regulation of and the priming for IL-12 production in DC form ideal targets for therapeutic intervention. The development of new therapies for atopic allergy now focuses on local IL-12-promoting substances to target both the development of new Th2 cells and the persistent population of established allergen-specific Th2 cells.

A region encompassing the FERM domain of Jak1 is necessary for binding to the cytokine receptor gp130.

The terminal portion of the Janus kinases (Jaks) contains a divergent FERM (Four-point-one, Ezrin, Radixin, Moesin) homology domain comprising 19 conserved hydrophobic regions. To determine the role of this domain in governing recruitment of Jak1, but not Jak3, to the gp130 subunit of the interleukin-6 family of cytokine receptors, the interaction of three Jak1/Jak3 chimeras with gp130 was investigated. Chimeras 1, 2 and 3 (Jak1 FERM regions 1-19, 1-18 and 1-8/Jak3, respectively) were all enzymically active. Chimeras 1 and 2 interacted with the cytoplasmic domain of gp130, although less efficiently than Jak1. Only chimera 2, however, restored gp130 signalling in Jak1-negative cells. The data are consistent with recruitment of Jak1 to gp130 through the Jak1 FERM domain, but also emphasise the likely requirement for precise Jak/receptor orientation to sustain function.

IL-12-induced reversal of human Th2 cells is accompanied by full restoration of IL-12 responsiveness and loss of GATA-3 expression.

IL-12 is a potent inducer of IFN-gamma production and drives the development of Th1 cells. Human polarized Th2 cells do not express the signaling beta2-subunit of the IL-12R and, therefore, do not signal in response to IL-12. The question was raised as to what extent the loss of the IL-12Rbeta2 chain in Th2 cells has bearing on the stability of the human Th2 phenotype. In the present report, we show that restimulation of human fully polarized Th2 cells in the presence of IL-12 primes for a shift towards Th0/Th1 phenotypes, accompanied by suppression of GATA-3 expression and induction of T-bet expression. These reversed cells are further characterized by a marked IL-12Rbeta2 chain expression and fully restored IL-12-inducible STAT4 activation. The IL-12-induced phenotypic shift proved to be stable as a subsequent restimulation in the presence of IL-4 and in the absence of IL-12 could not undo the accomplished changes. Identical results were obtained with cells from atopic patients, both with polyclonal Th2 cell lines and allergen-specific Th2 cell clones. These findings suggest the possibility of restoring IL-12 responsiveness in established Th2 cells of atopic patients by stimulation in the presence of IL-12, and that IL-12-promoting immunotherapy can be beneficial for Th2-mediated immune disorders, targeting both naive and memory effector T cells.

The paradigm of type 1 and type 2 antigen-presenting cells. Implications for atopic allergy.

Optimal clearance of the various pathogen types encountered by the human body requires the selective activation of particular cellular and/or humoral immune responses. The orchestration of the types of effector responses is directed by Th cells through the production of type 1 (Th1 cell-associated) and type 2 (Th2 cell-associated) cytokines. The way in which the Th cell cytokine profile is matched to the type of invading pathogen, and why these profiles sometimes derail and lead to disease, is not well understood. Here, we will discuss the concept that antigen-presenting cells (APC) provide Th cells not only with antigen and costimulatory signals, but also with a polarizing signal (signal 3). This signal can be mediated by many APC-derived factors, but IL-12 and PGE2 seem to be of major importance. The Th2-biased responses in atopic allergy appeared to be associated with monocytes with a decreased IL-12/PGE2 ratio and, consequently, with the down-regulation of type 1 cytokine production in Th cells. As for Th cells, APC can be functionialy polarized. In vitro experiments with monocyte-derived dendritic cells (DC) showed that the presence of IFN-gamma during activation of immature DC primes for mature DC with the ability of high IL-12 production and, consequently, a Th1-driving capacity (APC1 or DC1). In contrast, PGE2 primes for a low IL-12 production ability and a Th2-driving capacity (APC2 or DC2). These findings suggest that pathogens provoke either Th1- or Th2-cell development by inducing the production of a certain pattern of inflammatory DC-polarizing mediators (e.g. IFN-gamma and PGE2) at the site of infection. The type of immune polarization will not only depend on the type of pathogen, but also varies with the type of infected tissue, i.e. that different tissues produce different mediators in response to the same pathogen. In the case of atopic allergy, this concept implies that the Th2-cell bias may be related to low levels of cross-regulatory infections, to Th1 cell-inducing pathogens, or to an aberrant function of stromal cells in peripheral tissues.

Final maturation of dendritic cells is associated with impaired responsiveness to IFN-gamma and to bacterial IL-12 inducers: decreased ability of mature dendritic cells to produce IL-12 during the interaction with Th cells.

Activation of immature CD83- dendritic cells (DC) in peripheral tissues induces their maturation and migration to lymph nodes. Activated DC become potent stimulators of Th cells and efficient inducers of Th1- and Th2-type cytokine production. This study analyzes the ability of human monocyte-derived CD1a+ DC at different stages of IL-1 beta and TNF-alpha-induced maturation to produce the major Th1-driving factor IL-12. DC at the early stages of maturation (2 and 4 h) produced elevated amounts of IL-12 p70 during interaction with CD40 ligand-bearing Th cells or, after stimulation with the T cell-replacing factors, soluble CD40 ligand and IFN-gamma. The ability to produce IL-12 was strongly down-regulated at later time points, 12 h after the induction of DC maturation, and in fully mature CD83+ cells, at 48 h. In contrast, the ability of mature DC to produce IL-6 was preserved or even enhanced, indicating their intact responsiveness to CD40 triggering. A reduced IL-12-producing capacity of mature DC resulted mainly from their impaired responsiveness to IFN-gamma, a cofactor in CD40-induced IL-12 p70 production. This correlated with reduced expression of IFN-gamma R (CD119) by mature DC. In addition, while immature DC produced IL-12 and IL-6 after stimulation with LPS or Staphylococcus aureus Cowan I strain, mature DC became unresponsive to these bacterial stimuli. Together with the previously described ability of IL-10 and PGE2 to stably down-regulate the ability to produce IL-12 in maturing, but not in fully mature, DC, the current data indicate a general resistance of mature DC to IL-12-modulating factors.

High-level IL-12 production by human dendritic cells requires two signals.

IL-12 is a key cytokine in the development of Th1 responses. IL-12 production by antigen-presenting cells (APC) can be induced by the interaction between CD40 on the APC and CD40 ligand (CD40L) expressed on T cells after activation. Our previous study indicated that in dendritic cells (DC), the only APC that can activate naive T(h) cells efficiently, the mere CD40 engagement is insufficient to induce IL-12 production. The aim of the present study was to dissect the conditions for efficient IL-12 production by DC further. Using populations of naive and memory Th cells, recombinant CD40L, neutralizing and blocking antibodies, and by determining IFN-gamma production and CD40L expression levels, we here show that T cell-induced IL-12 production by DC results from the action of two signals, mediated by CD40L and IFN-gamma, and that the inability of naive T(h) cells to induce IL-12 production resides in their inability to produce IFN-(gamma). Other factors than CD40L and IFN-gamma can provide the required signals for IL-12 production by DC, as either factor could be replaced by lipopolysaccharide (LPS). The two-signal requirement proved unique for the production of IL-12, since either CD40 engagement or LPS was sufficient for the efficient production of tumor necrosis factor-alpha, IL-8 and the p40 subunit of IL-12, and may be considered as a safety mechanism for optimal control of potentially harmful T(h)1 responses.

Prostaglandin E2 induces the final maturation of IL-12-deficient CD1a+CD83+ dendritic cells: the levels of IL-12 are determined during the final dendritic cell maturation and are resistant to further modulation.

Activation of immature dendritic cells (DC) in peripheral tissues induces their migration to lymph nodes and their maturation into CD83+ DC, which are able to prime naive T cells. The inflammatory cytokines IL-1beta and TNF-alpha induce mature DC, which can secrete IL-12 and promote the development of Th0/Th1-biased cells. DC maturation factors with a Th2-promoting function have not been described. Here we show that PGE2, although it does not induce final DC maturation by itself, synergizes with IL-1beta and TNF-alpha, and allows their effectiveness at 100-fold lower concentrations. While being phenotypically identical with the DC matured in the presence of high concentrations of IL-1beta and TNF-alpha alone, DC matured in the additional presence of PGE2 show impaired IL-12 production and bias naive Th cell development toward the Th2. The ability of DC to produce IL-12 is also suppressed by IL-10, which in contrast to PGE2, inhibits their maturation. The differences in the ability to produce IL-12, established during the final DC maturation, are stable after the removal of modulatory factors. Importantly, fully mature DC become unsusceptible to PGE2 and IL-10. This indicates that the levels of IL-12 production in vivo, in mature DC interacting with Th cells within the lymph nodes, are mainly predetermined at the stage of immature DC in peripheral tissues. These data imply that the character of pathogen-induced local inflammatory reaction can "instruct" local DC to initiate Th1 or Th2-biased responses.

The role of antigen-presenting cells in the regulation of allergen-specific T cell responses.

Allergic reactions in atopic patients follow from a generalized enhanced polarization of Th cells, predominantly imposed by factors derived from antigen-presenting cells from a pathogen-stressed tissue; these sample information not only on antigen structures but also on the nature of the stress. Antigen-presenting cells of atopic individuals show aberrant characteristics which, through a highly interactive communication network, play an active role in aberrant Th-cell polarization. This generalized bias may follow from intrinsic abnormalities of antigen-presenting cells and also from a low degree of cross-regulation by micro-organisms.

Human dendritic cells require exogenous interleukin-12-inducing factors to direct the development of naive T-helper cells toward the Th1 phenotype.

Dendritic cells (DC) are important initiators of specific primary immune responses because they are the only APC that can efficiently activate naive Th cells. DC have the capacity to produce interleukin-12 (IL-12), a cytokine that plays a pivotal role in the development of Th1-mediated cellular immune responses. The present study focuses on the conditions under which human DC produce bioactive IL-12 p70 and, consequently, direct the development of naive T helper (Th) cells toward the Th1 phenotype. Bacteria or bacterial compounds such as Staphylococcus aureus Cowan strain I (SAC) or lipopolysaccharide (LPS) induced substantial IL-12 levels in DC, which could be further upregulated by interferon-gamma (IFN-gamma), whereas induction of IL-12 production via CD40 ligation required IFN-gamma as an obligatory, complementary signal. Also, activated naive Th cells were poor inducers of IL-12 production, unless exogenous IFN-gamma was present, whereas activated memory Th cells were effective inducers of IL-12 production and did not require exogenous IFN-gamma. Next, the cytokine profiles of matured Th cells that were primed by DC under different conditions were examined. DC promoted the development of naive Th cells into memory Th0 cells that produced both the type 1 cytokine IFN-gamma and the type 2 cytokine IL-4. In contrast, after activation with SAC, DC efficiently directed the development of Th1 cells through the release of IL-12. An APC-independent Th cell maturation model, using either recombinant IL-12 or supernatants of SAC-activated DC and neutralizing anti-IL-12 antibodies, confirmed that DC-derived IL-12 was the major Th1 skewing factor. Together, these data indicate that the contact between DC and naive Th cells during the initiation of specific immune responses does not result in the efficient induction of IL-12 production and that, consequently, exogenous IL-12-inducing factors are required to promote primary Th1-mediated cellular immune responses.

IL-12-deficient dendritic cells, generated in the presence of prostaglandin E2, promote type 2 cytokine production in maturing human naive T helper cells.

We studied to what extent the presence of an inflammatory mediator PGE2, during the development of dendritic cells (DC) affects their subsequent ability to induce Th1- and Th2-type cytokines in maturing naive Th cells. PGE2 (10(-9)-10(-6) M) did not alter the morphology or the expression of class II MHC and costimulatory molecules on DC obtained from monocytes in the presence of granulocyte-macrophage CSF and IL-4, although at concentrations above 10(-8) M, PGE2 prevented the acquisition of CD1a marker. Both control DC and DC maturing in the presence of PGE2 (PGE2-DC) were potent stimulators of naive Th cells. In contrast to control DC, which produced high amounts of IL-12 and trace amounts of IL-10, PGE2-DC produced no IL-12 and high amounts of IL-10 when stimulated in the absence of PGE2. This distinct cytokine profile of PGE2-DC was stable for at least 48 h of additional culture in the absence of PGE2. Control DC induced the development of Th0-like cells from superantigen-activated naive Th cells, whereas PGE2-DC promoted the development of Th cells that produced high amounts of IL-4 and IL-5. Experiments using IL-12-neutralizing Abs or rIL-12 indicated a crucial role of IL-12 deficiency in the induction of type 2 cytokine profiles. These findings suggest that elevated levels of PGE2 promote type 2 Th responses by stably impairing the ability of maturing DC to produce IL-12. Since type 2 Th responses are protective in several Th1-related autoimmune disorders, PGE2-DC may be considered for use in immunotherapy.

Dendritic cells, obtained from peripheral blood precursors in the presence of PGE2, promote Th2 responses.

In order to investigate the impact of an inflammatory mediator PGE2 on the functions of maturing DC we used an in vitro model of DC generation from peripheral blood monocytes. Addition of PGE2 (10(-9) M-10(-6) M) to the cultures performed in the presence of GM-CSF and IL-4 did not alter the morphology nor high levels of expression of class II MHC and co-stimulatory molecules on arising DC, although at concentrations above 10(-8) M, the acquisition of CD1a was selectively prevented. Control DC and the DC maturing in the presence of PGE2 (PGE2-DC) induced a similar proliferation of naive Th cells. Control DC produced high amounts of IL-12, and only trace amounts of IL-10, whereas PGE2-DC produced no IL-12 and high levels of IL-10, when stimulated after the removal of PGE2. The deficient IL-12 production by PGE2-DC was observed after stimulation both in the absence and in the presence of IFN gamma, and was not compensated during further 48 h culture in the absence of PGE2. Compared to control DC, PGE2-DC induced development of Th cells secreting elevated amounts of IL-4 and IL-5, from naive precursors. These data indicate that elevated tissue levels of PGE2 may promote type 2 Th responses by impairing the ability of locally maturing DC to produce IL-12. Since Th2 responses mediate protection in Th1-related autoimmune disorders, the use of PGE2-DC in immunotherapy of such disorders may be considered.