Kinetics of dendritic cells reconstitution and costimulatory molecules expression after myeloablative allogeneic haematopoetic stem cell transplantation: implications for the development of acute graft-versus host disease

Paired Donor and Recipient Immunophenotyping in Allogeneic Hematopoietic Stem Cell Transplantation: A Cellular Network Approach

Success and complications of allogeneic hematopoietic stem cell transplantation (alloHSCT) are closely connected to the transferred graft and immune reconstitution post alloHSCT. Due to the variety of immune cells and their distinct roles, a broad evaluation of the immune cellular network is warranted in mobilization and reconstitution studies in alloHSCT. Here, we propose a comprehensive phenotypic analysis of 26 immune cell subsets with multicolor flow cytometry from only 100µl whole blood per time point. Using this approach, we provide an extensive longitudinal analysis of almost 200 time points from 21 donor-recipient pairs. We observe a broad mobilization of innate and adaptive immune cell subsets after granulocyte-colony stimulating factor (G-CSF) treatment of healthy donors. Our data suggest that the relative quantitative immune cell subset composition in recipients approaches that of healthy donors from day +180 post alloHSCT onwards. Correlation of donor and recipient cell counts reveals distinct association patterns for different immune cell subsets and hierarchical clustering of recipient cell counts identifies distinct reconstitution groups in the first month after transplantation. We suggest our comprehensive immune subset analysis as a feasible and time efficient approach for a broad immune assessment for future clinical studies in the context of alloHSCT. This comprehensive cell composition assessment can be a critical step towards personalized graft composition strategies and individualized therapy management in areas such as GvHD prophylaxis in the highly complex immunological setting of alloHSCT.

Standardization of Workflow and Flow Cytometry Panels for Quantitative Expression Profiling of Surface Antigens on Blood Leukocyte Subsets: An HCDM CDMaps Initiative

Background

The Human Cell Differentiation Molecules (HCDM) organizes Human Leukocyte Differentiation Antigen (HLDA) workshops to test and name clusters of antibodies that react with a specific antigen. These cluster of differentiation (CD) markers have provided the scientific community with validated antibody clones, consistent naming of targets and reproducible identification of leukocyte subsets. Still, quantitative CD marker expression profiles and benchmarking of reagents at the single-cell level are currently lacking.

Objective

To develop a flow cytometric procedure for quantitative expression profiling of surface antigens on blood leukocyte subsets that is standardized across multiple research laboratories.

Methods

A high content framework to evaluate the titration and reactivity of Phycoerythrin (PE)-conjugated monoclonal antibodies (mAbs) was created. Two flow cytometry panels were designed: an innate cell tube for granulocytes, dendritic cells, monocytes, NK cells and innate lymphoid cells (12-color) and an adaptive lymphocyte tube for naive and memory B and T cells, including TCRγδ⁺, regulatory-T and follicular helper T cells (11-color). The potential of these 2 panels was demonstrated via expression profiling of selected CD markers detected by PE-conjugated antibodies and evaluated using 561 nm excitation.

Results

Using automated data annotation and dried backbone reagents, we reached a robust workflow amenable to processing hundreds of measurements in each experiment in a 96-well plate format. The immunophenotyping panels enabled discrimination of 27 leukocyte subsets and quantitative detection of the expression of PE-conjugated CD markers of interest that could quantify protein expression above 400 units of antibody binding capacity. Expression profiling of 4 selected CD markers (CD11b, CD31, CD38, CD40) showed high reproducibility across centers, as well as the capacity to benchmark unique clones directed toward the same CD3 antigen.

Conclusion

We optimized a procedure for quantitative expression profiling of surface antigens on blood leukocyte subsets. The workflow, bioinformatics pipeline and optimized flow panels enable the following: 1) mapping the expression patterns of HLDA-approved mAb clones to CD markers; 2) benchmarking new antibody clones to established CD markers; 3) defining new clusters of differentiation in future HLDA workshops.

Innate Immune Determinants of Graft-Versus-Host Disease and Bidirectional Immune Tolerance in Allogeneic Transplantation

The success of tissue transplantation from a healthy donor to a diseased individual (allo-transplantation) is regulated by the immune systems of both donor and recipient. Developing a state of specific non-reactivity between donor and recipient, while maintaining the salutary effects of immune function in the recipient, is called “immune (transplantation) tolerance”. In the classic early post-transplant period, minimizing bidirectional donor ←→ recipient reactivity requires the administration of immunosuppressive drugs, which have deleterious side effects (severe immunodeficiency, opportunistic infections, and neoplasia, in addition to drug-specific reactions and organ toxicities). Inducing immune tolerance directly through donor and recipient immune cells, particularly via subsets of immune regulatory cells, has helped to significantly reduce side effects associated with multiple immunosuppressive drugs after allo-transplantation. The innate and adaptive arms of the immune system are both implicated in inducing immune tolerance. In the present article, we will review innate immune subset manipulations and their potential applications in hematopoietic stem cell transplantation (HSCT) to cure malignant and non-malignant hematological disorders by inducing long-lasting donor ←→ recipient (bidirectional) immune tolerance and reduced graft-versus-host disease (GVHD). These innate immunotherapeutic strategies to promote long-term immune allo-transplant tolerance include myeloid-derived suppressor cells (MDSCs), regulatory macrophages, tolerogenic dendritic cells (tDCs), Natural Killer (NK) cells, invariant Natural Killer T (iNKT) cells, gamma delta T (γδ-T) cells and mesenchymal stromal cells (MSCs).

Dendritic Cell Recovery Impacts Outcomes after Umbilical Cord Blood and Sibling Donor Transplantation for Hematologic Malignancies

Dendritic cells (DCs) orchestrate immune responses after allogeneic hematopoietic cell transplantation (HCT). We studied the association of donor myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) recovery in the landmark analysis of umbilical cord blood (UCB) and matched related donor (RD) HCT. Eighty patients (42 UCB and 38 RD recipients) with a day 100 blood sample were included in the analysis. Median age was 51 years (range, 20 to 71). Most patients had acute leukemia (50%) or lymphoma (23%) and received reduced-intensity conditioning (75%). After transplantation, UCB recipients had higher DC counts than RD recipients reaching normal levels at day 100 after transplantation (UCB median 4.7 cells/µL versus RD median 1.7 cells/µL). UCB recipients with high day 100 pDCs levels (≥ median) had 2-fold lower risk of relapse compared with those with pDC^low (14% versus 28%, P = .29) and a trend to improved 1-year survival in multivariate analysis with hazard ratio of .22 (95% confidence interval, .04 to 1.05; P = .057). Cytomegalovirus (CMV) reactivation had adverse impact on DC reconstitution at day 100 in both UCB and RD groups and almost exclusively affected the mDC subset (CMV reactivation: mDC 3.2 cells/µL versus no CMV reactivation: 7.8 cells/µL; P = .004). Collectively, these data suggest that high levels of circulating pDCs at day 100 after UCB transplantation confer a survival advantage at 1 year.

TRAIL-mediated killing of acute lymphoblastic leukemia by plasmacytoid dendritic cell-activated natural killer cells

Acute lymphoblastic leukemia (ALL) still frequently recurs after hematopoietic stem cell transplantation (HSCT), underscoring the need to improve the graft-versus-leukemia (GvL) effect. Natural killer (NK) cells reconstitute in the first months following HSCT when leukemia burden is at its lowest, but ALL cells have been shown to be resistant to NK cell-mediated killing. We show here that this resistance is overcome by NK cell stimulation with TLR-9-activated plasmacytoid dendritic cells (pDCs). NK cell priming with activated pDCs resulted in TRAIL and CD69 up-regulation on NK cells and IFN-γ production. NK cell activation was dependent on IFN-α produced by pDCs, but was not reproduced by IFN-α alone. ALL killing was further enhanced by inhibition of KIR engagement. We showed that ALL lysis was mainly mediated by TRAIL engagement, while the release of cytolytic granules was involved when ALL expressed NK cell activating receptor ligands. Finally, adoptive transfers of activated-pDCs in ALL-bearing humanized mice delayed the leukemia onset and cure 30% of mice. Our data therefore demonstrate that TLR-9 activated pDCs are a powerful tool to overcome ALL resistance to NK cell-mediated killing and to reinforce the GvL effect of HSCT. These results open new therapeutic avenues to prevent relapse in children with ALL.

Plasmacytoid dendritic cells in allogeneic hematopoietic cell transplantation: benefit or burden?

Plasmacytoid dendritic cells (pDCs) bridge innate and adaptive immune responses and have important roles in hematopoietic engraftment, GvHD and graft-versus-leukemia responses following allogeneic hematopoietic cell transplantation (HCT). In addition, pDCs mediate antiviral immunity, particularly as they are the body's primary cellular source of type I interferon. Given their pleiotropic roles, pDCs have emerged as cells that critically impact transplant outcomes, including overall survival. In this article, we will review the pre-clinical and clinical literature, supporting the crucial roles that pDCs assume as key immune effector cells during HCT.

Immune Reconstitution after Allogeneic Hematopoietic Cell Transplantation in Children

Allogeneic (allo) hematopoietic cell transplantation (HCT) has evolved into a potent curative treatment option for a variety of malignant and nonmalignant diseases. The occurrence of complications and mortality after allo-HCT is, however, still high and is strongly associated with immune reconstitution (IR). Therefore, detailed information on IR through immunomonitoring is crucial to improve survival chances after HCT. To date, information about the reconstituting immune system after allo-HCT in pediatric patients is mostly derived from routine standard-of-care measurements. More profound knowledge on IR may provide tools to better predict and modulate adverse reactions and, subsequently, improve survival chances. Here, we provide an overview of IR (eg, immune cell subsets and circulating chemokines/cytokines) after allo-HCT in children, taking into account different cell sources and serotherapy, and discuss strategies to enhance immunomonitoring. We conclude that available IR data after allo-HCT contain limited information on immune cell families (mostly only generic T, B, and NK cells), which would improve with more detailed information on reconstituting cell subsets or effector cell functionality at earlier time points (<1 month). In addition, secretome data (eg, multiplex cytokine/chemokine profiles) could add to the understanding of IR mechanisms and cell functionality and may even provide (early) biomarkers for individual disease outcome, such as viral reactivity, graft-versus-host disease, or graft-versus-leukemia. The present data and suggestions for more detailed, standardized, and harmonized immunomonitoring in future (pediatric) allo-HCT studies will pave the path to "precision transplantation:" an individualized HCT approach (including conditioning), based on detailed information on IR and biomarkers, aiming to reduce transplantation related mortality and relapse, and subsequently improve survival chances.

Dendritic cell chimerism in oral mucosa of transplanted patients affected by graft-versus-host disease

OBJECTIVE

Graft-versus-host disease (GVHD) is one of the main complications after haematopoietic stem cell transplantation. Clinical features of GVHD include either an acute (aGVHD) or a chronic (cGVHD) condition that affects locations such as the oral mucosa. While the involvement of the host's dendritic cells (DCs) has been demonstrated in aGVHD, the origin (donor/host) and mechanisms underlying oral cGVHD have not been completely elucidated. In this study, we intend to determine the origin of DCs present in mucosal tissue biopsies from the oral cavity of transplanted patients affected by cGVHD.

METHODS

We purified DCs, from oral biopsies of three patients with cGVHD, through immunobeads and subsequently performed DNA extraction. The origin of the obtained DCs was determined by PCR amplification of 13 informative short tandem repeat (STR) alleles. We also characterised the DCs phenotype and the inflammatory infiltrate from biopsies of two patients by immunohistochemistry.

RESULTS

Clinical and histological features of the biopsies were concordant with oral cGVHD. We identified CD11c-, CD207- and CD1a-positive cells in the epithelium and beneath the basal layer. Purification of DCs from the mucosa of patients affected by post-transplantation cGVHD was >95%. PCR-STR data analysis of DCs DNA showed that 100% of analysed cells were of donor origin in all of the evaluated patients.

CONCLUSION

Our results demonstrate that resident DCs isolated from the oral tissue of allotransplanted patients affected by cGVHD are originated from the donor. Further research will clarify the role of DCs in the development and/or severity of oral cGVHD.

Peripheral Blood Plasmacytoid Dendritic Cells at Day 100 Can Predict Outcome after Allogeneic Stem Cell Transplantation

The rapidly increasing use of allogeneic stem cell transplantation (allo-SCT) emphasizes the need for identifying variables predictive of its outcome. Plasmacytoid dendritic cells (pDCs) play a major role in establishing immune competence and in several autoimmune diseases. Thus, we investigated whether pDCs might influence the outcome of patients after allo-SCT in 79 consecutive patients who underwent this procedure. pDCs were identified in the blood of patients at day 100 after allo-SCT by staining peripheral blood mononuclear cells for surface markers and intracellular cytokines and analyzing them on a flow cytometer. We found the pDC level at day 100 was not influenced by patient or graft characteristics, and only the absence of previous grades II to IV acute graft-versus-host disease was significantly associated with higher levels of blood pDCs after allo-SCT (OR, .67; 95% CI, .54 to .83; P = .0004). Using the median value of pDCs at day 100 to divide the patients into 2 distinct groups, we observed that a low pDC level was correlated with a worse overall survival (55% versus 86%, P = .007). In a multivariate analysis, only low pDC level (OR, 3.41; 95% CI, 1.19 to 9.79; P = .02) and older patient age (OR, 5.16; 95% CI, 1.15 to 23.14; P = .03) were significantly predictive of increased risk of death. We conclude that monitoring of pDC may be useful for patient management and may have a significant impact on the probability of a favorable outcome of allo-SCT.

Low Counts of Plasmacytoid Dendritic Cells after Engraftment Are Associated with High Early Mortality after Allogeneic Stem Cell Transplantation

Dendritic cells (DCs) are antigen-presenting cells that drive immune responses and tolerance and are divided in different subsets: myeloid DCs (mDCs: lineage-; HLA-DR+, 11c+), plasmacytoid dendritic cells (pDCs: HLA-DR+, CD123+), and monocyte-derived DCs (moDC: lineage-, 11c+, 16+). After hematopoietic stem cell transplantation (HSCT), low DC counts in the recipients' peripheral blood (PB) have been associated with worse outcomes, but the relevance of DC graft content remains unclear, and there are few data in the setting of unrelated donor HSCT. We evaluated the DC graft content and monitored DC recovery in PB from 111 HSCT recipients (median age, 17 years; range 1 to 74), who received bone marrow (46%), umbilical cord blood (32%), or PB (22%) from unrelated (81%) or related donors (19%). In 86 patients with sustained allogeneic recovery, patients with higher counts of all DC subsets (pDC, mDC, and moDC) 3 weeks after engraftment had lower incidence of nonrelapse mortality (NMR) and acute graft-versus-host disease (aGVHD) and better survival. pDC counts were associated with more striking results: patients with higher pDC counts had much lower incidences of NRM (3% versus 47%, P < .0001), lower incidence of aGVHD (24% versus 67%, P < .0001), and better overall survival (92% versus 45%, P < .0001). In contrast, higher pDC counts in the graft was associated with an increased risk of aGVHD (55% versus 26%, P = .02). Our results indicate that DC counts are closely correlated with HSCT outcomes and warrant further prospective evaluation and possible early therapeutic interventions to ameliorate severe aGVHD and decrease mortality.

Impaired interferon-alpha production by plasmacytoid dendritic cells after cord blood transplantation in children: implication for post-transplantation toll-like receptor ligand-based immunotherapy

Plasmacytoid dendritic cells (pDCs) initiate both innate and adaptive immune responses, making them attractive targets for post-transplantation immunotherapy, particularly after cord blood transplantation (CBT). Toll-like receptor (TLR) agonists are currently studied for pDC stimulation in various clinical settings. Their efficacy depends on pDC number and functionality, which are unknown after CBT. We performed a longitudinal study of pDC reconstitution in children who underwent bone marrow transplantation (BMT) and single-unit CBT. Both CBT and unrelated BMT patients received antithymocyte globulin as part of their graft-versus-host disease prophylaxis regimen. pDC blood counts were higher in CBT patients than in healthy volunteers from 2 to 9 months after transplantation, whereas they remained lower in BMT patients. We showed that cord blood progenitors gave rise in vitro to a 500-fold increase in functional pDCs over bone marrow counterparts. Upon stimulation with a TLR agonist, pDCs from both CBT and BMT recipients upregulated T cell costimulatory molecules, whereas interferon-alpha (IFN-α) production was impaired for 9 months after CBT. TLR agonist treatment is thus not expected to induce IFN-α production by pDCs after CBT, limiting its immunotherapeutic potential. Fortunately, in vitro production of large amounts of functional pDCs from cord blood progenitors paves the way for the post-transplantation adoptive transfer of pDCs.

Decreased dendritic cell numbers but increased TLR9-mediated interferon-alpha production in first degree relatives of type 1 diabetes patients

OBJECTIVE

Dendritic cells (DCs) play an important role in pathogenesis of autoimmunity, including type 1 diabetes (T1D). In this study, we investigated DC subpopulations and their responses to TLR stimulation in T1D patients and their relatives.

METHODS

We analyzed the frequency of myeloid (mDCs) and plasmacytoid DCs (pDCs) in 97 T1D patients (69 onset, 28 long-term), 67 first-degree relatives, and 64 controls. We additionally tested the IFN-alpha production by pDCs upon stimulation with TLR 7, 8 and 9 agonists.

RESULTS

A lower number of mDCs and pDCs were found in T1D patients and their relatives. Of all the tested TLR ligands, only stimulation with CpG 2216 induced IFN-alpha production that was the highest in T1D relatives, except of autoantibody-negative relatives bearing the protective haplotypes.

CONCLUSION

Our data demonstrate disturbances in DC number and function expressed most significantly in T1D relatives and point to a potential role of TLR9-induced IFN-alpha production in T1D development.

The role of dendritic cells in graft-versus-tumor effect

Dendritic cells (DCs) are the most potent antigen presenting cells. DCs play a pivotal role in determining the character and magnitude of immune responses to tumors. Host and donor hematopoietic-derived DCs play a critical role in the development of graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation. GVHD is tightly linked with the graft-versus-tumor (GVT) effect. Although both host and donor DCs are important regulators of GVHD, the role of DCs in GVT is poorly understood. GVT is caused by donor T cells that attack recipient tumor cells. The donor T cells recognize alloantigens, and tumor specific antigens (TSAs) are mediating GVHD. The process of presentation of these antigens, especially TSAs remains unknown. Recent data suggested that DC may be essential role for inducing GVT. The mechanisms that DCs possess may include direct presentation, cross-presentation, cross-dressing. The role they play in GVT will be reviewed.

Saikosaponin-d affects the differentiation, maturation and function of monocyte-derived dendritic cells

Saikosaponin-d (Ssd) is a triterpenoid saponin derived from Bupleurum falcatum L., which has been shown to exhibit a variety of pharmacological properties, including anti-inflammatory, antibacterial and antiviral properties. The aim of the present study was to investigate the effect of Ssd on the differentiation, maturation and function of human monocyte-derived dendritic cells (DCs) isolated from condylomata acuminata patients. The results of the present study demonstrated that Ssd reduced the differentiation of DCs, as evidenced by decreased expression levels of cluster of differentiation (CD)1a, CD80 and CD86 molecules and increased CD14 expression. Expression levels of the mannose receptor and CD32 were also significantly elevated, which was associated with enhanced fluorescein isothiocyanate-dextran endocytic activity. Furthermore, Ssd treatment promoted DC maturation by increasing the expression levels of CD40, CD83, CD80 and CD86. In addition, the function of mature DCs, including the secretion of IL-12 and the stimulation of lymphocyte proliferation, was significantly increased following Ssd administration. In conclusion, the present study indicated that Ssd exhibited immunomodulatory effects and may be a novel potent chemopreventive drug candidate for the treatment of condylomata acuminata.

Saikosaponin-d affects the differentiation, maturation and function of monocyte-derived dendritic cells

Saikosaponin-d (Ssd) is a triterpenoid saponin derived from Bupleurum falcatum L., which has been shown to exhibit a variety of pharmacological properties, including anti-inflammatory, antibacterial and antiviral properties. The aim of the present study was to investigate the effect of Ssd on the differentiation, maturation and function of human monocyte-derived dendritic cells (DCs) isolated from condylomata acuminata patients. The results of the present study demonstrated that Ssd reduced the differentiation of DCs, as evidenced by decreased expression levels of cluster of differentiation (CD)1a, CD80 and CD86 molecules and increased CD14 expression. Expression levels of the mannose receptor and CD32 were also significantly elevated, which was associated with enhanced fluorescein isothiocyanate-dextran endocytic activity. Furthermore, Ssd treatment promoted DC maturation by increasing the expression levels of CD40, CD83, CD80 and CD86. In addition, the function of mature DCs, including the secretion of IL-12 and the stimulation of lymphocyte proliferation, was significantly increased following Ssd administration. In conclusion, the present study indicated that Ssd exhibited immunomodulatory effects and may be a novel potent chemopreventive drug candidate for the treatment of condylomata acuminata.

Targeting CD83 for the treatment of graft-versus-host disease

Graft-versus-host disease (GVHD) is a common and often fatal complication of bone marrow transplantation. Antigen-presenting cells from donor and recipient play a critical role in the initiation and maintenance of GVHD. CD83, which is expressed in activated lymphocytes and dendritic cells, is regarded as a marker of mature dendritic cells. Targeting CD83 using soluble CD83 molecules or antibodies has been demonstrated to have therapeutic effects against GVHD in preclinical models. Understanding the biological function of CD83 and the underlying mechanisms through which targeting CD83 attenuates GVHD is likely to greatly improve current treatments and provide new methods for the treatment of GVHD.

Reconstitution of 6-sulfo LacNAc dendritic cells after allogeneic stem-cell transplantation

BACKGROUND

Infections and acute graft-versus-host disease (GvHD) represent major complications of allogeneic stem-cell transplantation (SCT). Dendritic cells (DCs) display an extraordinary capacity to induce innate and adaptive immune responses. Therefore, they play a crucial role in the elimination of pathogens and in the pathogenesis of acute GvHD. 6-Sulfo LacNAc DCs (slanDCs) are a major subpopulation of human blood DCs with a high proinflammatory capacity. We investigated for the first time the reconstitution of slanDCs in the blood of patients after SCT and the modulation of their frequency by bacterial infection, cytomegalovirus (CMV) reactivation, and acute GvHD.

METHODS

The frequency of slanDCs, CD1c myeloid DCs (mDCs), and plasmacytoid DCs (pDCs) in the peripheral blood was quantified by flow cytometry in 80 patients after SCT. To assess individual DC subsets, we used pregating of the HLADRLin subset and antibodies against slanDCs, blood DC antigen 1 (CD1c mDCs), and blood DC antigen 2 (pDCs).

RESULTS

SlanDCs showed the slowest reconstitution in the first month after SCT compared with CD1c mDCs and pDCs. Interestingly, in the second and third months after SCT, their percentage steadily increased, and slanDCs were the most abundant DC subset. In addition, we observed a markedly reduced frequency of slanDCs in the blood of patients with bacterial infection, CMV reactivation, or severe acute GvHD. Furthermore, slanDCs showed the most prominent reduction after steroid treatment of acute GvHD.

CONCLUSIONS

These results indicate that SCT-associated complications such as bacterial infection, CMV reactivation, and acute GvHD can significantly modulate the frequency of slanDCs.

Selective increase in blood dendritic cell antigen-3-positive dendritic cells in bronchoalveolar lavage fluid in allergic patients

Dendritic cells (DCs) are specific antigen-presenting cells that play critical roles in the initiation and polarization of immune responses. DCs residing in the lungs might be detected in the bronchoalveolar lavage fluid (BALF). We analysed DC compartment in the peripheral blood and BALF of patients with allergy and in controls. Plasmacytoid and four distinct subsets of myeloid DCs [characterized by the expression of blood dendritic cell antigen (BDCA)-1+ and -3+ and CD16 positivity or negativity] were detected in both tested compartments. We further evaluated the expression of C-type lectins [mannose receptor (MR), dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) and dendritic and epithelial cells (DEC)-205] relevant to the pathogenesis of asthma. Interestingly, we found a selective increase in the frequency of myeloid DC-expressing BDCA-3 and MR particularly in BALF from allergic patients. Specific and highly statistically significant increase in BDCA-3+ and/or MR+ DCs brings a novel characteristic to BAL analysis in allergic patients.

Case report: type 1 diabetes in monozygotic quadruplets

Type 1 diabetes (T1D) is an autoimmune disease characterized by the lack of insulin due to an autoimmune destruction of pancreatic beta cells. Here, we report a unique case of a family with naturally conceived quadruplets in which T1D was diagnosed in two quadruplets simultaneously. At the same time, the third quadruplet was diagnosed with the pre-diabetic stage. Remarkably, all four quadruplets were positive for anti-islet cell antibodies, GAD65 and IA-A2. Monozygotic status of the quadruplets was confirmed by testing 14 different short tandem repeat polymorphisms. Serological examination confirmed that all quadruplets and their father suffered from a recent enteroviral infection of EV68-71 serotype. To assess the nature of the molecular pathological processes contributing to the development of diabetes, immunocompetent cells isolated from all family members were characterized by gene expression arrays, immune-cell enumerations and cytokine-production assays. The microarray data provided evidence that viral infection, and IL-27 and IL-9 cytokine signalling contributed to the onset of T1D in two of the quadruplets. The propensity of stimulated immunocompetent cells from non-diabetic members of the family to secrete high level of IFN-α further corroborates this conclusion. The number of T regulatory cells as well as plasmacytoid and/or myeloid dendritic cells was found diminished in all family members. Thus, this unique family is a prime example for the support of the so-called 'fertile-field' hypothesis proposing that genetic predisposition to anti-islet autoimmunity is 'fertilized' and precipitated by a viral infection leading to a fully blown T1D.

The potential of patients' peripheral blood mononuclear cells to differentiate into dendritic cells after hematopoietic stem cell transplantation

AIMS

Although hematopoietic stem cell transplantation (HSCT) is a curative treatment for many hematological disorders, there is persistent immunosuppression in both allogeneic and autologous HSCT. Dendritic cells (DCs) play key roles in the immune system. This study investigated whether the DC progenitor cells within patients' peripheral blood after HSCT have the potential to differentiate into DCs.

MAIN METHODS

Twenty-eight patients were included in this study, and peripheral blood samples were basically taken before starting the conditioning regimen, on the day of transplantation (day 0), and on days +14, +28, +42, +70 and +170 after transplantation. Immature DCs (iDCs) were induced from adherent mononuclear cells by using recombinant human granulocyte-macrophage colony-stimulating factor plus interleukin-4.

KEY FINDINGS

The iDCs expressed cell surface antigens such as CD40 and HLA-DR, and they had phagocytotic activity, thus showing the characteristics of iDCs. The induction of iDCs was possible from day +14 after HSCT. However, there were differences between allogeneic and autologous HSCT in the expression of CCR5 in iDCs at day +14 after transplantation. Furthermore, the up-regulation of maturation-related antigens by maturation stimuli was higher after HSCT compared with before HSCT.

SIGNIFICANCE

We demonstrated that patients' peripheral blood mononuclear cells have the potential to differentiate into DCs beginning on day +14 after HSCT, although some differences exist between allogeneic and autologous HSCT and between before and after HSCT.

Preconditioning therapy with lentiviral vector-programmed dendritic cells accelerates the homeostatic expansion of antigen-reactive human T cells in NOD.Rag1-/-.IL-2rγc-/- mice

Dendritic cell (DC)-based immunization is a potent strategy to direct prompt and durable immune responses against viral reactivations after transplantations. Here, we show that overnight lentiviral vector (LV) gene transfer into human monocytes co-expressing granulocyte-macrophage colony stimulating factor and interleukin (IL)-4 induced self-differentiated DCs (SMART-DCs) with stable DC immunophenotype over weeks in culture and secreted several inflammatory cytokines. SMART-DCs injected subcutaneously in immunodeficient NOD.Rag1(-/-).IL2rγ(-/-) (NRG) mice 1 day after LV transduction were stable for a month in vivo. "Conventional" DCs (cDCs) and SMART-DCs were compared with regard to their potency to accelerate the expansion, biodistribution, and antigenic stimulation of autologous human T cells. Peripheral blood cells obtained from human cytomegalovirus (hCMV)-reactive donors and full-length hCMV pp65 antigenic protein or peptides were used. DCs loaded with pp65 were administered subcutaneously into NRG mice as a preconditioning treatment a week prior to intravenous infusion with T cells. Optical imaging analyses demonstrated that in mice preconditioned with SMART-DC-pp65, T cells were directly recruited to the immunization site and subsequently spread to the spleen and other organs. A dramatic expansion of both human CD8(+) and CD4(+) T cells could be observed within a few days after infusion, and this was associated with consistent measurable CD8(+) effector memory T-cell responses against different pp65 epitopes. Thus, this mouse model demonstrates the proof-of-principle for SMART-DCs to accelerate expansion of human lymphocytes, resulting in poly-functional and antigen-specific immune responses against hCMV-pp65.

Dendritic cell recovery post-lymphodepletion: a potential mechanism for anti-cancer adoptive T cell therapy and vaccination

Adoptive transfer of autologous tumor-reactive T cells holds promise as a cancer immunotherapy. In this approach, T cells are harvested from a tumor-bearing host, expanded in vitro and infused back to the same host. Conditioning of the recipient host with a lymphodepletion regimen of chemotherapy or radiotherapy before adoptive T cell transfer has been shown to substantially improve survival and anti-tumor responses of the transferred cells. These effects are further enhanced when the adoptive T cell transfer is followed by vaccination with tumor antigens in combination with a potent immune adjuvant. Although significant progress has been made toward an understanding of the reasons underlying the beneficial effects of lymphodepletion to T cell adoptive therapy, the precise mechanisms remain poorly understood. Recent studies, including ours, would indicate a more central role for antigen presenting cells, in particular dendritic cells. Unraveling the exact role of these important cells in mediation of the beneficial effects of lymphodepletion could provide novel pathways toward the rational design of more effective anti-cancer immunotherapy. This article focuses on how the frequency, phenotype, and functions of dendritic cells are altered during the lymphopenic and recovery phases post-induction of lymphodepletion, and how they affect the anti-tumor responses of adoptively transferred T cells.

Paricalcitol (19-nor-1,25-dihydroxyvitamin D2) and calcitriol (1,25-dihydroxyvitamin D3) exert potent immunomodulatory effects on dendritic cells and inhibit induction of antigen-specific T cells

Paricalcitol (19-nor-1,25/OH(2)/D(2)), a second generation vitamin D receptor (VDR) activator, is a synthetic analogue of vitamin D3. In contrast to calcitriol, paricalcitol has a reduced effect on intestinal calcium resorption thus avoiding undesirable hypercalcemia. Information about immunomodulatory activity of paricalcitol is scarce. In this study we show that, in all investigated aspects, paricalcitol retains significant immunomodulatory activity, comparable to calcitriol. Both VDR agonists impaired differentiation of immature dendritic cells (DCs) from monocytes. The presence of VDR agonists during DC differentiation abolished their capacity to be activated and, despite potent Toll-like receptor mediated stimulation, VDR agonist-treated DCs remained in the immature state. In accordance with these findings, VDR-treated DCs produced no bioactive IL-12 and had a significantly decreased capacity to induce antigen-specific T cells while the capacity to induce functional Tregs remained unchanged when compared to control DCs. As DCs and T cells play an important role in the pathogenesis of atherosclerosis, in end-stage renal disease patients, paricalcitol should be a VDR agonist of choice for the reduction of the risk of atherosclerosis due to its immunomodulatory effect proven in this study and known limited hypercalcemic effect. The immunomodulatory potency of paricalcitol makes it a drug of interest in the therapy of chronic immune-mediated inflammatory diseases.