Granulocyte-colony stimulating factor drives the in vitro differentiation of human dendritic cells that induce anergy in naïve T cells

Haploidentical transplants with a G-CSF/ATG-based protocol: Experience from China

Haploidentical donor stem cell transplantation (haplo-SCT) has made great advances in recent decades. The granulocyte colony-stimulating factor (G-CSF)- and antithymocyte globulin (ATG)-based protocol, which is known as the Beijing Protocol, represents one of the current T-cell repletion strategies in haplo-SCT. The key elements of the Beijing Protocol for graft versus host disease (GvHD) prophylaxis include G-CSF inducing T-cell tolerance and altering graft cell components, as well as ATG administration exerting an immunoregulatory effect for intensive prophylaxis. This review will summarize the GvHD incidence, the underlying novel mechanism for GvHD prophylaxis, how to optimize GvHD prophylaxis, and the recent advances of the Beijing Protocol, mainly focusing on the issues of GvHD.

Generation of Human Regulatory Dendritic Cells from Cryopreserved Healthy Donor Cells and Hematopoietic Stem Cell Transplant Recipients

Acute graft versus host disease (GVHD) remains a significant complication following hematopoietic stem cell transplant (HSCT), despite improved human leukocyte antigen (HLA) matching and advances in prophylactic treatment regimens. Previous studies have shown promising results for future regulatory dendritic cell (DCreg) therapies in the amelioration of GVHD. This study evaluates the effects of cryopreservation on the generation of DCreg, the generation of young and older DCreg in serum-free media, and the feasibility of generating DCreg from young and older HSCT patient monocytes. DCregs were generated in X-vivo 15 serum-free media from donor or patient monocytes. This study includes the use of monocytes from young and older healthy, donor, and HSCT patients with varying hematological diseases. Phenotypic differences in cell populations were assessed via flow cytometry while pro-inflammatory and anti-inflammatory cytokine production was evaluated in culture medium. The number of DCreg generated from cryopreserved monocytes of healthy donors was not significantly different from freshly isolated monocytes. DCreg generated from cryopreserved monocytes had comparable levels of co-stimulatory molecule expression, inhibitory molecule expression, and cytokine production as freshly isolated monocytes. Young and older healthy donor monocytes generated similar numbers of DCreg with similar cytokine production and phenotype. Although monocytes from older HSCT patients generated significantly fewer DCreg, DCreg from young and older HSCT patients had comparable phenotypes and cytokine production. Monocytes from young and older myelodysplastic syndrome (MDS) patients generated reduced numbers of DCreg compared to non-MDS-derived DCreg. We demonstrate that the cryopreservation of monocytes from HSCT patients of varying hematological diseases allows for the cost-effective generation of DCreg on an as-needed basis. Although the generation of DCreg from MDS patients requires further assessment, these data support the possibility of in vitro-generated DCreg as a therapy to reduce GVHD-associated morbidity and mortality in young and older HSCT recipients.

Contrariety of Human Bone Marrow Mesenchymal Stromal Cell Functionality in Modulating Circulatory Myeloid and Plasmacytoid Dendritic Cell Subsets

Mesenchymal Stromal Cells (MSCs) derived from bone marrow are widely tested in clinical trials as a cellular therapy for potential inflammatory disorders. The mechanism of action of MSCs in mediating immune modulation is of wide interest. In the present study, we investigated the effect of human bone-marrow-derived MSCs in modulating the circulating peripheral blood dendritic cell responses through flow cytometry and multiplex secretome technology upon their coculture ex vivo. Our results demonstrated that MSCs do not significantly modulate the responses of plasmacytoid dendritic cells. However, MSCs dose-dependently promote the maturation of myeloid dendritic cells. Mechanistic analysis showed that dendritic cell licensing cues (Lipopolysaccharide and Interferon-gamma) stimulate MSCs to secret an array of dendritic cell maturation-associated secretory factors. We also identified that MSC-mediated upregulation of myeloid dendritic cell maturation is associated with the unique predictive secretome signature. Overall, the present study demonstrated the dichotomy of MSC functionality in modulating myeloid and plasmacytoid dendritic cells. This study provides clues that clinical trials need to investigate if circulating dendritic cell subsets in MSC therapy can serve as potency biomarkers.

Single-cell clonal tracking of persistent T-cells in allogeneic hematopoietic stem cell transplantation

The critical balance between intended and adverse effects in allogeneic hematopoietic stem cell transplantation (alloHSCT) depends on the fate of individual donor T-cells. To this end, we tracked αβT-cell clonotypes during stem cell mobilization treatment with granulocyte-colony stimulating factor (G-CSF) in healthy donors and for six months during immune reconstitution after transfer to transplant recipients. More than 250 αβT-cell clonotypes were tracked from donor to recipient. These clonotypes consisted almost exclusively of CD8⁺ effector memory T cells (CD8TEM), which exhibited a different transcriptional signature with enhanced effector and cytotoxic functions compared to other CD8TEM. Importantly, these distinct and persisting clonotypes could already be delineated in the donor. We confirmed these phenotypes on the protein level and their potential for selection from the graft. Thus, we identified a transcriptional signature associated with persistence and expansion of donor T-cell clonotypes after alloHSCT that may be exploited for personalized graft manipulation strategies in future studies.

Immunomodulatory effects of G-CSF in cancer: Therapeutic implications

Numerous preclinical studies have reported a pro-tumour role for granulocyte colony-stimulating factor (G-CSF) that is predominantly mediated by neutrophils and MDSCs, the major G-CSF receptor expressing populations. In the presence of G-CSF (either tumour-derived or exogenous) these myeloid populations commonly exhibit a T cell suppressive phenotype. However, the direct effects of this cytokine on other immune lineages, such as T and NK cells, are not as well established. Herein we discuss the most recent data relating to the effect of G-CSF on the major immune populations, exclusively in the context of cancer. Recent publications have drawn attention to the other tumour-promoting effects of G-CSF on myeloid cells, including NETosis, promotion of cancer stemness and skewed differentiation of bone marrow progenitors towards myelopoiesis. Although G-CSF is safely and commonly used as a supportive therapy to prevent or treat chemotherapy-associated neutropenia in cancer patients, we also discuss the potential impacts of G-CSF on other anti-cancer treatments. Importantly, considerations for immune checkpoint blockade are highlighted, as many publications report a T cell suppressive effect of G-CSF that may diminish the effectiveness of this immunotherapy.

Innate Immune Cells in Pressure Overload-Induced Cardiac Hypertrophy and Remodeling

Pressure overload and heart failure are among the leading causes of cardiovascular morbidity and mortality. Accumulating evidence suggests that inflammatory cell activation and release of inflammatory mediators are of vital importance during the pathogenesis of these cardiac diseases. Yet, the roles of innate immune cells and subsequent inflammatory events in these processes remain poorly understood. Here, we outline the possible underlying mechanisms of innate immune cell participation, including mast cells, macrophages, monocytes, neutrophils, dendritic cells, eosinophils, and natural killer T cells in these pathological processes. Although these cells accumulate in the atrium or ventricles at different time points after pressure overload, their cardioprotective or cardiodestructive activities differ from each other. Among them, mast cells, neutrophils, and dendritic cells exert detrimental function in experimental models, whereas eosinophils and natural killer T cells display cardioprotective activities. Depending on their subsets, macrophages and monocytes may exacerbate cardiodysfunction or negatively regulate cardiac hypertrophy and remodeling. Pressure overload stimulates the secretion of cytokines, chemokines, and growth factors from innate immune cells and even resident cardiomyocytes that together assist innate immune cell infiltration into injured heart. These infiltrates are involved in pro-hypertrophic events and cardiac fibroblast activation. Immune regulation of cardiac innate immune cells becomes a promising therapeutic approach in experimental cardiac disease treatment, highlighting the significance of their clinical evaluation in humans.

Granulocyte colony-stimulating factor is not pathogenic in lupus nephritis

Systemic lupus erythematosus (lupus) is an autoimmune disease characterized by autoantibodies that form immune complexes with self‐antigens, which deposit in various tissues, leading to inflammation and disease. The etiology of disease is complex and still not completely elucidated. Dysregulated inflammation is an important disease feature, and the mainstay of lupus treatment still utilizes nonspecific anti‐inflammatory drugs. Granulocyte colony‐stimulating factor (G‐CSF) is a growth, survival, and activation factor for neutrophils and a mobilizer of hematopoietic stem cells, both of which underlie inflammatory responses in lupus. To determine whether G‐CSF has a causal role in lupus, we genetically deleted G‐CSF from Lyn‐deficient mice, an experimental model of lupus nephritis. Lyn^−/−G‐CSF^−/− mice displayed many of the inflammatory features of Lyn‐deficient mice; however, they had reduced bone marrow and tissue neutrophils, consistent with G‐CSF's role in neutrophil development. Unexpectedly, in comparison to aged Lyn‐deficient mice, matched Lyn^−/−G‐CSF^−/− mice maintained neutrophil hyperactivation and exhibited exacerbated numbers of effector memory T cells, augmented autoantibody titers, and worsened lupus nephritis. In humans, serum G‐CSF levels were not elevated in patients with lupus or with active renal disease. Thus, these studies suggest that G‐CSF is not pathogenic in lupus, and therefore G‐CSF blockade is an unsuitable therapeutic avenue.

Contrasting Immunopathogenic and Therapeutic Roles of Granulocyte Colony-Stimulating Factor in Cancer

Tumor cells are particularly adept at exploiting the immunosuppressive potential of neutrophils as a strategy to achieve uncontrolled proliferation and spread. Recruitment of neutrophils, particularly those of an immature phenotype, known as granulocytic myeloid-derived suppressor cells, is achieved via the production of tumor-derived granulocyte colony-stimulating factor (G-CSF) and neutrophil-selective chemokines. This is not the only mechanism by which G-CSF contributes to tumor-mediated immunosuppression. In this context, the G-CSF receptor is expressed on various cells of the adaptive and innate immune systems and is associated with induction of T cell polarization towards the Th2 and regulatory T cell (Treg) phenotypes. In contrast to the potentially adverse effects of sustained, endogenous production of G-CSF by tumor cells, stringently controlled prophylactic administration of recombinant (r) G-CSF is now a widely practiced strategy in medical oncology to prevent, and in some cases treat, chemotherapy-induced severe neutropenia. Following an overview of the synthesis, structure and function of G-CSF and its receptor, the remainder of this review is focused on: (i) effects of G-CSF on the cells of the adaptive and innate immune systems; (ii) mechanisms by which this cytokine promotes tumor progression and invasion; and (iii) current clinical applications and potential risks of the use of rG-CSF in medical oncology.

Generation of Powerful Human Tolerogenic Dendritic Cells by Lentiviral-Mediated IL-10 Gene Transfer

The prominent role of dendritic cells (DC) in promoting tolerance and the development of methods to generate clinical grade products allowed the clinical application of tolerogenic DC (tolDC)-based therapies for controlling unwanted immune responses. We established an efficient method to generate tolerogenic human DC, producing supra-physiological levels of IL-10, by genetically engineering monocyte-derived DC with a bidirectional Lentiviral Vector (bdLV) encoding for IL-10 and a marker gene. DC^IL−10 are mature DC, modulate T cell responses, promote T regulatory cells, and are phenotypically and functionally stable upon stimulation. Adoptive transfer of human DC^IL−10 in a humanized mouse model dampens allogeneic T cell recall responses, while murine DC^IL−10 delays acute graft-vs.-host disease in mice. Our report outlines an efficient method to transduce human myeloid cells with large-size LV and shows that stable over-expression of IL-10 generates an effective cell product for future clinical applications in the contest of allogeneic transplantation.

Combined GM-CSF and G-CSF administration mobilizes CD4+ CD25hi Foxp3hi Treg in leukapheresis products of rhesus monkeys

Early phase clinical trials are evaluating the feasibility, safety, and therapeutic potential of ex vivo expanded regulatory T cells (Treg) in transplantation. A limitation is the paucity of naturally occurring Treg numbers in peripheral blood. Hence, protracted ex vivo expansion is required to obtain sufficient Treg in order to meet target cell doses. Because cytokine administration has been used successfully to mobilize immune cells to the peripheral blood in experimental and clinical studies, we hypothesized that granulocyte macrophage-colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) administration would enhance Treg percentages in leukapheresis products of rhesus monkeys. Following combined GM-CSF and G-CSF administration, the incidence of Treg in peripheral blood and leukapheresis products was elevated significantly, where approximately 3.7 × 10⁶ /kg CD4⁺ CD25^hi Foxp3^hi or 6.8 × 10⁶ /kg CD4⁺ CD25^hi CD127^lo Treg can be collected from individual products. Mobilized Treg expressed a comparable repertoire of surface markers, chemokine receptors, and transcription factors to naïve monkey peripheral blood Treg. Furthermore, when expanded ex vivo, mobilized leukapheresis product and peripheral blood Treg exhibited similar ability to suppress autologous CD4⁺ and CD8⁺ T cell proliferation. These observations indicate that leukapheresis products from combined GM-CSF- and G-CSF-mobilized individuals are a comparatively rich source of Treg and may circumvent long-term ex vivo expansion required for therapeutic application.

Granulocyte Colony-Stimulating Factor-Primed Unmanipulated Haploidentical Blood and Marrow Transplantation

Granulocyte colony-stimulating factor (G-CSF), a growth factor for neutrophils, has been successfully used for stem cell mobilization and T cell immune tolerance induction. The establishment of G-CSF-primed unmanipulated haploidentical blood and marrow transplantation (The Beijing Protocol) has achieved outcomes for the treatment of acute leukemia, myelodysplastic syndrome, and severe aplastic anemia with haploidentical allografts comparable to those of human leukocyte antigen (HLA)-matched sibling donor transplantation. Currently, G-CSF-mobilized bone marrow and/or peripheral blood stem cell sources have been widely used in unmanipulated haploidentical transplant settings. In this review, we summarize the roles of G-CSF in inducing T cell immune tolerance. We discuss the recent advances in the Beijing Protocol, mainly focusing on strategies that have been used to improve transplant outcomes in cases of poor graft function, virus infections, and relapse. The application of G-CSF-primed allografts in other haploidentical modalities is also discussed.

The roles of CSFs on the functional polarization of tumor-associated macrophages

Macrophages have a central role in numerous physiological processes, such as immune defense, maintenance of tissue homeostasis, wound healing, and inflammation. Moreover, in numerous severe disorders, such as cancer or chronic inflammation, their functions can be profoundly affected. Macrophages continuously sense their environment and adapt their phenotypes and functions to the local requirements; this process is called plasticity. In addition to stress signals, metabolites, and direct cell-contact interactions with surrounding cells, numerous cytokines play a central role in controlling macrophage polarization. In this review, we will focus on three human macrophage differentiation factors: macrophage colony-stimulating factor (M-CSF), IL-34, and granulocyte M-CSF. These CSFs allow human monocyte survival, promote their differentiation into macrophages, and control macrophage polarization as they give rise to cells with different phenotype and functions. Based on recent observations, the role of granulocyte CSF on macrophage polarization is also addressed. Finally, our current knowledge on the expression of these growth factors in tumor microenvironment and their impact on the generation and polarization of tumor-associated macrophages are summarized.

Lymphoproliferative responses to dendritic cell presentation of sensitizing allergens in atopic children with multiple allergies

BACKGROUND

Peripheral blood mononuclear cells (PBMCs) proliferate inconsistently, rendering current lymphoproliferation assays unreliable in diagnosis.

OBJECTIVE

To investigate the utility and nature of proliferation responses in allergy by comparison of the standard lymphoproliferation with a new dendritic cell (DC) stimulated assay.

METHODS

Monocyte-derived DCs were pulsed with allergens and incubated with autologous T cells for 7 days. DC-stimulated and standard PBMC proliferation responses to 3 common dietary allergens in children with allergy and without atopy were measured by incorporation of tritiated thymidine and reduction of carboxyl fluorescein succinimidyl ester staining.

RESULTS

The DC presentation of sensitizing allergens induced significantly higher proliferative responses than PBMC stimulation (P = .04) and greater distinction between normal and allergic responses. DC-induced stimulation indices of children without sensitivity and those with allergy were significantly different with all 3 foods (P < .001). All children with allergy presented with peanut allergy and 12 of 14 (86%) β-lactoglobulin-pulsed DC preparations proliferated more than 3.3-fold above un-pulsed cells, but 8 of 18 children (44%) with ovalbumin egg allergy showed proliferation below this level. The stimulation index of DC tritiated thymidine incorporation correlated closely with carboxyl fluorescein succinimidyl ester reduction (P < .001). Sensitivity of detection of peanut, milk, or egg allergy was 100%, 85.7%, or 55.6% and specificity was 60%, 88.9%, or 86.7%, respectively. DC-stimulated T cells expressed increased levels of CD45 RO and CD25 and most produced interferon-γ. DC-stimulated proliferation correlated with total immunoglobulin E and peanut antigen-stimulated proliferation correlated with peanut specific immunoglobulin E (P = .03).

CONCLUSION

The DC-induced lymphoproliferation had higher sensitivity, specificity, and reproducibility than the standard assay and caused increased memory and activated T-cell proliferation in children with food allergy.

Antigen delivery to dendritic cells shapes human CD4+ and CD8+ T cell memory responses to Staphylococcus aureus

Intracellular persistence of Staphylococcus aureus favors bacterial spread and chronic infections. Here, we provide evidence for the existence of human CD4⁺ and CD8⁺ T cell memory against staphylococcal antigens. Notably, the latter could provide a missing link in our understanding of immune control of intracellular S. aureus. The analyses showed that pulsing of monocyte-derived dendritic cells (MoDC) with native staphylococcal protein antigens induced release of Th2-associated cytokines and mediators linked to T regulatory cell development (G-CSF, IL-2 and IL-10) from both CD4⁺ and CD8⁺ T cells, thus revealing a state of tolerance predominantly arising from preformed memory T cells. Furthermore, G-CSF was identified as a suppressor of CD8⁺ T cell-derived IFNγ secretion, thus confirming a tolerogenic role of this cytokine in the regulation of T cell responses to S. aureus. Nevertheless, delivery of in vitro transcribed mRNA-encoded staphylococcal antigens triggered Th1-biased responses, e.g. IFNγ and TNF release from both naïve and memory T cells. Collectively, our data highlight the potential of mRNA-adjuvanted antigen presentation to enable inflammatory responses, thus overriding the existing Th2/Treg-biased memory T cell response to native S. aureus antigens.

Staphylococcus aureus is deemed one of the most important nosocomial pathogens but, to date, there are no safe and protective vaccines. In this study we investigate the nature of the preformed T cell response to S. aureus antigens in healthy donors. Our data reveal that CD4⁺ and—so far not described—CD8⁺ T cell memory responses against native staphylococcal antigens exist but are skewed towards minimizing inflammation and promoting tolerance. The T cell response to staphylococcal antigens is characterized by the secretion of typical Th2 cytokines such as IL-5 and IL-13 and mediators associated with formation of T regulatory cells. Most importantly, G-CSF suppresses IFNγ release from pre-existent memory T cells. However, our data reveal that the use of mRNA-encoded antigens to trigger S. aureus-specific T cell responses bears the potential to override the tolerogenic bias. It favors TNF- and IFNγ-releasing T cells and may, thus, represent an innovative tool in prophylactic and therapeutic vaccine development.

G-CSF and Exenatide Might Be Associated with Increased Long-Term Survival of Allogeneic Pancreatic Islet Grafts

Background

Allogeneic human islet transplantation is an effective therapy for the treatment of patients with Type 1 Diabetes (T1D). The low number of islet transplants performed worldwide and the different transplantation protocols used limit the identification of the most effective therapeutic options to improve the efficacy of this approach.

Methods

We present a retrospective analysis on the data collected from 44 patients with T1D who underwent islet transplantation at our institute between 2000 and 2007. Several variables were included: recipient demographics and immunological characteristics, donor and transplant characteristics, induction protocols, and additional medical treatment received. Immunosuppression was induced with anti-CD25 (Daclizumab), alone or in association with anti-tumor necrosis factor alpha (TNF-α) treatments (Etanercept or Infliximab), or with anti-CD52 (Alemtuzumab) in association with anti-TNF-α treatments (Etanercept or Infliximab). Subsets of patients were treated with Filgrastim for moderate/severe neutropenia and/or Exenatide for post prandial hyperglycemia.

Results

The analysis performed indicates a negative association between graft survival (c-peptide level ≥ 0.3 ng/ml) and islet infusion volume, with the caveat that, the progressive reduction of infusion volumes over the years has been paralleled by improved immunosuppressive protocols. A positive association is instead suggested between graft survival and administration of Exenatide and Filgrastim, alone or in combination.

Conclusion

This retrospective analysis may be of assistance to further improve long-term outcomes of protocols for transplant of islets and other organs.

Human monocytes undergo functional re-programming during differentiation to dendritic cell mediated by human extravillous trophoblasts

Maternal immune adaptation is required for a successful pregnancy to avoid rejection of the fetal–placental unit. Dendritic cells within the decidual microenvironment lock in a tolerogenic profile. However, how these tolerogenic DCs are induced and the underlying mechanisms are largely unknown. In this study, we show that human extravillous trophoblasts redirect the monocyte-to-DC transition and induce regulatory dendritic cells. DCs differentiated from blood monocytes in the presence of human extravillous trophoblast cell line HTR-8/SVneo displayed a DC-SIGN⁺CD14⁺CD1a⁻ phenotype, similar with decidual DCs. HTR8-conditioned DCs were unable to develop a fully mature phenotype in response to LPS, and altered the cytokine secretory profile significantly. Functionally, conditioned DCs poorly induced the proliferation and activation of allogeneic T cells, whereas promoted CD4⁺CD25⁺Foxp3⁺ Treg cells generation. Furthermore, the supernatant from DC and HTR-8/SVneo coculture system contained significant high amount of M-CSF and MCP-1. Using neutralizing antibodies, we discussed the role of M-CSF and MCP-1 during monocyte-to-DCs differentiation mediated by extravillous trophoblasts. Our data indicate that human extravillous trophoblasts play an important role in modulating the monocyte-to-DC differentiation through M-CSF and MCP-1, which facilitate the establishment of a tolerogenic microenvironment at the maternal–fetal interface.

Therapeutic Potential of Hyporesponsive CD4(+) T Cells in Autoimmunity

The interaction between dendritic cells (DCs) and T cells is crucial on immunity or tolerance induction. In an immature or semi-mature state, DCs induce tolerance through T-cell deletion, generation of regulatory T cells, and/or induction of T-cell anergy. Anergy is defined as an unresponsive state that retains T cells in an “off” mode under conditions in which immune activation is undesirable. This mechanism is crucial for the control of T-cell responses against self-antigens, thereby preventing autoimmunity. Tolerogenic DCs (tDCs), generated in vitro from peripheral blood monocytes of healthy donors or patients with autoimmune pathologies, were shown to modulate immune responses by inducing T-cell hyporesponsiveness. Animal models of autoimmune diseases confirmed the impact of T-cell anergy on disease development and progression in vivo. Thus, the induction of T-cell hyporesponsiveness by tDCs has become a promising immunotherapeutic strategy for the treatment of T-cell-mediated autoimmune disorders. Here, we review recent findings in the area and discuss the potential of anergy induction for clinical purposes.

Controlled release strategies for modulating immune responses to promote tissue regeneration

Advances in the field of tissue engineering have enhanced the potential of regenerative medicine, yet the efficacy of these strategies remains incomplete, and is limited by the innate and adaptive immune responses. The immune response associated with injury or disease combined with that mounted to biomaterials, transplanted cells, proteins, and gene therapies vectors can contribute to the inability to fully restore tissue function. Blocking immune responses such as with anti-inflammatory or immunosuppressive agents are either ineffective, as the immune response contributes significantly to regeneration, or have significant side effects. This review describes targeted strategies to modulate the immune response in order to limit tissue damage following injury, promote an anti-inflammatory environment that leads to regeneration, and induce antigen (Ag)-specific tolerance that can target degenerative diseases that destroy tissues and promote engraftment of transplanted cells. Focusing on targeted immuno-modulation, we describe local delivery techniques to sites of inflammation as well as systemic approaches that preferentially target subsets of immune populations.

Assessment of the effector function of CMV-specific CTLs isolated using MHC-multimers from granulocyte-colony stimulating factor mobilized peripheral blood

BACKGROUND

Adoptive transfer of CMV-specific T cells has shown promising results in preventing pathological effects caused by opportunistic CMV infection in immunocompromised patients following allogeneic hematopoietic stem cell transplantation. The majority of studies have used steady-state leukapheresis for CMV-reactive product manufacture, a collection obtained prior to or months after G-CSF mobilization, but the procurement of this additional sample is often not available in the unrelated donor setting. If the cellular product for adoptive immunotherapy could be generated from the same G-CSF mobilized collection, the problems associated with the additional harvest could be overcome. Despite the tolerogenic effects associated with G-CSF mobilization, recent studies described that CMV-primed T cells generated from mobilized donors remain functional.

METHODS

MHC-multimers are potent tools that allow the rapid production of antigen-specific CTLs. Therefore, in the present study we have assessed the feasibility and efficacy of CMV-specific CTL manufacture from G-CSF mobilized apheresis using MHC-multimers.

RESULTS

CMV-specific CTLs can be efficiently isolated from G-CSF mobilized samples with Streptamers and are able to express activation markers and produce cytokines in response to antigenic stimulation. However, this anti-viral functionality is moderately reduced when compared to non-mobilized products.

CONCLUSIONS

The translation of Streptamer technology for the isolation of anti-viral CTLs from G-CSF mobilized PBMCs into clinical practice would widen the number of patients that could benefit from this therapeutic strategy, although our results need to be taken into consideration before the infusion of antigen-specific T cells obtained from G-CSF mobilized samples.

HLA-G expression levels influence the tolerogenic activity of human DC-10

Human leukocyte antigen (HLA)-G is a non-classical HLA class I molecule with known immune-modulatory functions. Our group identified a subset of human dendritic cells, named DC-10, that induce adaptive interleukin-10-producing T regulatory type 1 (Tr1) cells via the interleukin-10-dependent HLA-G/ILT4 pathway. In this study we aimed at defining the role of HLA-G in DC-10-mediated Tr1 cell differentiation. We analyzed phenotype, functions, and genetic variations in the 3' untranslated region of the HLA-G locus of in vitro-differentiated DC-10 from 67 healthy donors. We showed that HLA-G expression on DC-10 is donor-dependent. Functional studies demonstrated that DC-10, independently of HLA-G expression, secrete interleukin-10 and negligible levels of interleukin-12. Interestingly, DC-10 with high HLA-G promote allo-specific anergic T cells that contain a significantly higher frequency of Tr1 cells, defined as interleukin-10-producing (P=0.0121) or CD49b(+)LAG-3(+) (P=0.0031) T cells, compared to DC-10 with low HLA-G. We found that the HLA-G expression on DC-10 is genetically imprinted, being associated with specific variations in the 3' untranslated region of the gene, and it may be finely tuned by microRNA-mediated post-transcriptional regulation. These data highlight the important role of HLA-G in boosting DC-10 tolerogenic activity and confirm that interleukin-10 production by DC-10 is necessary but not sufficient to promote Tr1 cells at high frequency. These new insights into the role of HLA-G in DC-10-mediated induction of Tr1 cells provide additional information for clinical use in Tr1- or DC-10-based cell therapy approaches.

HLA-G as a tolerogenic molecule in transplantation and pregnancy

HLA-G is a nonclassical HLA class I molecule. In allogeneic situations such as pregnancy or allograft transplantation, the expression of HLA-G has been related to a better acceptance of the fetus or the allograft. Thus, it seems that HLA-G is crucially involved in mechanisms shaping an allogeneic immune response into tolerance. In this contribution we focus on (i) how HLA-G is involved in transplantation and human reproduction, (ii) how HLA-G is regulated by genetic and microenvironmental factors, and (iii) how HLA-G can offer novel perspectives with respect to therapy.

Who is the best donor for a related HLA haplotype-mismatched transplant?

The best donor for a related donor for a human leukocyte antigen (HLA) haplotype-mismatched transplant for hematological neoplasms is controversial. We studied outcomes in 1210 consecutive transplant recipients treated on a uniform protocol. Younger donors and male donors were associated with less nonrelapse mortality (NRM; hazard ratio [HR] = 0.30; 95% confidence interval [CI] = 0.01-0.39; P = .008 and HR = 0.65; 95% CI = 0.49-0.85; P = .002) and better survival (HR = 0.73; 95% CI = 0.54-0.97; P = .033 and HR = 0.73; 95% CI = 0.59-0.91; P = .005). Father donors were associated with less NRM (HR = 0.65; 95% CI = 0.45-0.95; P = .02), acute graft-versus-host disease (GVHD) (HR = 0.69; 95% CI = 0.55-0.86; P = .001), and better survival (HR = 0.66; 95% CI = 0.50-0.87; P = .003) compared with mother donors. Children donors were associated with less acute GVHD than sibling donors (HR = 0.57; 95% CI = 0.31-0.91; P = .01). Older sister donors were inferior to father donors with regard to NRM (HR = 1.87; 95% CI = 1.10-3.20; P = .02) and survival (HR = 1.59; 95% CI = 1.05-2.40; P = .03). Noninherited maternal antigen-mismatched sibling donors were associated with the lowest incidence of acute GVHD compared with parental donors and noninherited paternal antigen-mismatched sibling donors. Specific HLA disparities were not significantly correlated with transplant outcomes. Our data indicate which HLA haplotype-mismatched related donors are associated with the best transplant outcomes in persons with hematological neoplasms.

Haploidentical SCT: the mechanisms underlying the crossing of HLA barriers

Research on the different mechanisms for crossing HLA barriers has progressed over the past 10 years. General outlines have come into view for a solution to this issue and are often presented as 'haploidentical SCT' immunology. In this review, we discuss several mechanisms that have recently been described in ex vivo and in vivo settings that can either avoid GVHD or promote hematopoietic reconstitution in haploidentical settings. The host and donor T-cell responses to allogeneic HLA molecules are a fundamental obstacle to the successful application of haploidentical transplantation, which results in unacceptably high incidences of GVHD and graft rejection. Thus, the T-cell response is a central factor in the establishment of a novel haploidentical transplant protocol with superior outcomes.

Tr1 cells and the counter-regulation of immunity: natural mechanisms and therapeutic applications

T regulatory Type 1 (Tr1) cells are adaptive T regulatory cells characterized by the ability to secrete high levels of IL-10 and minimal amounts of IL-4 and IL-17. Recently, CD49b and LAG-3 have been identified as Tr1-cell-specific biomarkers in mice and humans. Tr1 cells suppress T-cell- and antigen-presenting cell- (APC) responses primarily via the secretion of IL-10 and TGF-β. In addition, Tr1 cells release granzyme B and perforin and kill myeloid cells. Tr1 cells inhibit T cell responses also via cell-contact dependent mechanisms mediated by CTLA-4 or PD-1, and by disrupting the metabolic state of T effector cells via the production of the ectoenzymes CD39 and CD73. Tr1 cells were first described in peripheral blood of patients who developed tolerance after HLA-mismatched fetal liver hematopoietic stem cell transplant. Since their discovery, Tr1 cells have been proven to be important in maintaining immunological homeostasis and preventing T-cell-mediated diseases. Furthermore, the possibility to generate and expand Tr1 cells in vitro has led to their utilization as cellular therapy in humans. In this chapter we summarize the unique and distinctive biological properties of Tr1 cells, the well-known and newly discovered Tr1-cell biomarkers, and the different methods to induce Tr1 cells in vitro and in vivo. We also address the role of Tr1 cells in infectious diseases, autoimmunity, and transplant rejection in different pre-clinical disease models and in patients. Finally, we highlight the pathological settings in which Tr1 cells can be beneficial to prevent or to cure the disease.

Molecular pathways: human leukocyte antigen G (HLA-G)

Human leukocyte antigen G (HLA-G) is a nonclassical MHC class I molecule that exerts important tolerogenic functions. Its main physiologic expression occurs in the placenta, where it participates in the maternal tolerance toward the fetus. HLA-G expression was found in embryonic tissues, in adult immune privileged organs, and in cells of the hematopoietic lineage. It is expressed in various types of primary solid (melanoma, head and neck, lung, urogenital, gastrointestinal, and breast cancers) and hematologic malignancies (acute leukemia, lymphomas) and metastases. HLA-G ectopic expression is observed in cancer, suggesting that its expression is one strategy used by tumor cells to escape immune surveillance. In this review, we will focus on HLA-G expression in cancers and its association with the prognosis. We will highlight the underlying molecular mechanisms of impaired HLA-G expression, the immune tolerant function of HLA-G in tumors, and the potential diagnostic use of membrane-bound and soluble HLA-G as a biomarker to identify tumors and to monitor disease stage. As HLA-G is a potent immunoinhibitory molecule, its blockade remains an attractive therapeutic strategy against cancer. Elimination of HLA-G-expressing cancer cells would be important in the efficacy of anticancer therapies.

CCL22-producing CD8α- myeloid dendritic cells mediate regulatory T cell recruitment in response to G-CSF treatment

G-CSF prevents type 1 diabetes in the NOD mouse by promoting the local recruitment of T regulatory cells (Tregs). This is an indirect effect because adoptive transfer of G-CSF-induced tolerogenic dendritic cells (DCs) promotes Treg accumulation. However, the identity of the particular DC subset and the molecule(s) mediating this effect remain unknown. We demonstrate in this study that the adoptive transfer of CD11c(high)CD8α(-) DCs isolated from pegylated G-CSF (pegG-CSF) recipients, but not that of other DC subtypes, enhanced the pancreatic recruitment of CD4(+)CD25(+)Foxp3(+) Tregs, which generated increased amounts of TGF-β. Likewise, only CD11c(high)CD8α(-) DCs from pegG-CSF recipients secreted the chemokine CCL22 at levels that effectively attracted Tregs. PegG-CSF was more efficient at enhancing the synthesis of CCL22 by CD11c(high)CD8α(-) DCs from the pancreatic lymph nodes compared with those from the spleen. Accordingly, CD11c(high)CD8α(-) DCs from the pancreatic lymph nodes of pegG-CSF recipients were more efficient than their splenic counterparts in the recruitment of Tregs upon adoptive transfer. Predictably, CD11c(high)CD8α(-) DCs failed to recruit these Tregs both in vivo and in vitro following intracellular neutralization of CCL22. These data assign a key role to CD8α(-) DCs and CCL22 in Treg recruitment in the protection of NOD mice against type 1 diabetes following the treatment with G-CSF.

Comparative analysis of monocyte subsets in the pig

Human and mouse monocyte can be divided into two different subpopulations based on surface marker expression: CD14/16 and Ly6C/CX3CR1, respectively. Monocyte subpopulations in the pig were identified based on reciprocal expression of CD14 and the scavenger receptor CD163. The two populations, CD14(hi)-CD163(low) and CD14(low)-CD163(hi), show approximately equal abundance in the steady-state. Culture of pig PBMCs in CSF1 indicates that the two populations are a maturation series controlled by this growth factor. Gene expression in pig monocyte subpopulations was profiled using the newly developed and annotated pig whole genome snowball microarray. Previous studies have suggested a functional equivalence between human and mouse subsets, but certain genes such as CD36, CLEC4E, or TREM-1 showed human-specific expression. The same genes were expressed selectively in pig monocyte subsets. However, the profiles suggest that the pig CD14(low)-CD163(high) cells are actually equivalent to intermediate human monocytes, and there is no CD14(-) CD16(+) "nonclassical" population. The results are discussed in terms of the relevance of the pig as a model for understanding human monocyte function.

Semen promotes the differentiation of tolerogenic dendritic cells

Seminal plasma is not just a carrier for spermatozoa. It contains high concentrations of cytokines, chemokines, and other biological compounds that are able to exert potent effects on the immune system of the receptive partner. Previous studies have shown that semen induces an acute inflammatory response at the female genital mucosa after coitus. Moreover, it induces regulatory mechanisms that allow the fetus (a semiallograft) to grow and develop in the uterus. The mechanisms underlying these regulatory mechanisms, however, are poorly understood. In this study, we show that seminal plasma redirects the differentiation of human dendritic cells (DCs) toward a regulatory profile. DCs differentiated from human monocytes in the presence of high dilutions of seminal plasma did not express CD1a but showed high levels of CD14. They were unable to develop a fully mature phenotype in response to LPS, TNF-α, CD40L, Pam2CSK4 (TLR2/6 agonist), or Pam3CSK4 (TLR1/2 agonist). Upon activation, they produced low amounts of the inflammatory cytokines IL-12p70, IL-1β, TNF-α, and IL-6, but expressed a high ability to produce IL-10 and TGF-β. Inhibition of the PG receptors E-prostanoid receptors 2 and 4 prevented the tolerogenic effect induced by seminal plasma on the phenotype and function of DCs, suggesting that E-series PGs play a major role. By promoting a tolerogenic profile in DCs, seminal plasma might favor fertility, but might also compromise the capacity of the receptive partner to mount an effective immune response against sexually transmitted pathogens.

Human tolerogenic DC-10: perspectives for clinical applications

Dendritic cells (DCs) are critically involved in inducing either immunity or tolerance. During the last decades efforts have been devoted to the development of ad hoc methods to manipulate DCs in vitro to enhance or stabilize their tolerogenic properties. Addition of IL-10 during monocyte-derived DC differentiation allows the induction of DC-10, a subset of human tolerogenic DCs characterized by high IL-10/IL-12 ratio and co-expression of high levels of the tolerogenic molecules HLA-G and immunoglobulin-like transcript 4. DC-10 are potent inducers of adaptive type 1 regulatory T cells, well known to promote and maintain peripheral tolerance. In this review we provide an in-depth comparison of the phenotype and mechanisms of suppression mediated by DC-10 and other known regulatory antigen-presenting cells currently under clinical development. We discuss the clinical therapeutic application of DC-10 as inducers of type 1 regulatory T cells for tailoring regulatory T-cell-based cell therapy, and the use of DC-10 as adoptive cell therapy for promoting and restoring tolerance in T-cell-mediated diseases.

The immunosuppressive molecule HLA-G and its clinical implications

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex (MHC) class I molecule that, through interaction with its receptors, exerts important tolerogenic functions. Its main physiological expression occurs in placenta where it seems to participate in the maternal tolerance toward the fetus. HLA-G has been studied as a marker of pregnancy complications such as abortion or pre-eclapmsia. Although HLA-G is not expressed in most adult tissues, its ectopic expression has been observed in some diseases such as viral infections, autoimmune disorders, and especially cancer. HLA-G neo-expression in cancer is associated with the capability of tumor cells to evade the immune control. In this review, we will summarize HLA-G biology and how it participates in these physiopathological processes. Special attention will be paid to its role as a diagnostic tool and also as a therapeutic target.

Leukotriene C(4) prevents the complete maturation of murine dendritic cells and modifies interleukin-12/interleukin-23 balance

Leukotriene C(4) is an important mediator in the development of inflammatory reactions and ischaemia. Previous studies have shown that leukotriene C(4) is able to modulate the function of dendritic cells (DCs) and induce their chemotaxis from skin to lymph node. In this study, we decided to evaluate the modulation exerted by leukotriene C(4) on DCs, depending on their status of activation. We showed for the first time that leukotriene C(4) stimulates endocytosis both in immature and lipopolysaccharide (LPS) -activated DCs. Moreover, it suppressed the interleukin-12p70 (IL-12p70) release, but induces the secretion of IL-23 by DCs activated with LPS and promotes the expansion of T helper type 17 (Th17) lymphocytes. Furthermore, blocking the release of IL-23 reduced the percentages of CD4(+) T cells producing IL-17 in a mixed lymphocyte reaction. Ours results suggest that leukotriene C(4) interferes with the complete maturation of inflammatory DCs in terms of phenotype and antigen uptake, while favouring the release of IL-23, the main cytokine involved in the maintenance of the Th17 profile.

The tolerogenic interplay(s) among HLA-G, myeloid APCs, and regulatory cells

Myeloid antigen-presenting cells (APCs), regulatory cells, and the HLA-G molecule are involved in modulating immune responses and promoting tolerance. APCs are known to induce regulatory cells and to express HLA-G as well as 2 of its receptors; regulatory T cells can express and act through HLA-G; and HLA-G has been directly involved in the generation of regulatory cells. Thus, interplay(s) among HLA-G, APCs, and regulatory cells can be easily envisaged. However, despite a large body of evidence on the tolerogenic properties of HLA-G, APCs, and regulatory cells, little is known on how these tolerogenic players cooperate. In this review, we first focus on key aspects of the individual relationships between HLA-G, myeloid APCs, and regulatory cells. In its second part, we highlight recent work that gathers individual effects and demonstrates how intertwined the HLA-G/myeloid APCs/regulatory cell relationship is.

Tolerogenic dendritic cells and rheumatoid arthritis: current status and perspectives

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by the influxation of synovia and synovial compartments with immune cells including dendritic cells (DCs). DCs that induce autoimmune tolerance are called tolerogenic DCs (tolDCs). As a promising immunotherapeutic strategy for RA, tolDCs have received increasing attention. In this review, we first introduce the significant role of tolDCs in autoimmune regulation and then describe the manipulation strategies to generate tolDCs; next, we summarize recent progress in the experimental application of tolDCs for RA therapy, and finally we discuss the perspectives of tolerogenic vaccination for the treatment for RA in clinic.

Clinical tolerance in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) has been a curative therapeutic option for a wide range of immune hematologic malignant and non-malignant disorders including genetic diseases and inborn errors. Once in the host, allogeneic transplanted cells have not only to ensure myeloid repopulation and immunological reconstitution but also to acquire tolerance to host human leukocyte antigens via central or peripheral mechanisms. Peripheral tolerance after allogeneic HSCT depends on several regulatory mechanisms aimed at blocking alloimmune reactivity while preserving immune responses to pathogens and tumor antigens. Patients transplanted with HSCT represent an ideal model system in humans to identify and characterize the key cellular and molecular players underlying these mechanisms. The knowledge gained from these studies has allowed the development of novel therapeutic strategies aimed at inducing long-term peripheral tolerance, which can be applicable not only in allogeneic HSCT but also in autoimmune diseases and solid-organ transplantation. In the present review, we describe Type 1 regulatory T cells, initially discovered and characterized in chimeric patients transplanted with human leukocyte antigen-mismatched HSCT, and how their presence correlates to tolerance induction and maintenance. Furthermore, we summarize different cell therapy approaches with regulatory T cells, designed to facilitate tolerance induction, minimizing pharmaceutical interventions.

Effects of pegylated G-CSF on immune cell number and function in patients with gynecological malignancies

Background

Pegylated granulocyte colony-stimulating factor (G-CSF; pegfilgrastim) is a longer-acting form of G-CSF, whose effects on dendritic cell (DC) and regulatory T cell (Treg) mobilization, and on the in vivo and ex vivo release of immune modulating cytokines remain unexplored.

Methods

Twelve patients with gynecological cancers received carboplatin/paclitaxel chemotherapy and single-dose pegfilgrastim as prophylaxis of febrile neutropenia. Peripheral blood was collected prior to pegfilgrastim administration (day 0) and on days +7, +11 and +21, to quantify immunoregulatory cytokines and to assess type 1 DC (DC1), type 2 DC (DC2) and Treg cell mobilization. In vitro-differentiated, monocyte-derived DC were used to investigate endocytic activity, expression of DC maturation antigens and ability to activate allogeneic T-cell proliferation.

Results

Pegfilgrastim increased the frequency of circulating DC1 and DC2 precursors. In contrast, CD4⁺FoxP3⁺ bona fide Treg cells were unchanged compared with baseline. Serum levels of hepatocyte growth factor and interleukin (IL)-12p40, but not transforming growth factor-β1 or immune suppressive kynurenines, significantly increased after pegfilgrastim administration. Interestingly, pegfilgrastim fostered in vitro monocytic secretion of IL-12p40 and IL-12p70 when compared with unconjugated G-CSF. Finally, DC populations differentiated in vitro after clinical provision of pegfilgrastim were phenotypically mature, possessed low endocytic activity, and incited a robust T-cell proliferative response.

Conclusions

Pegfilgrastim induced significant changes in immune cell number and function. The enhancement of monocytic IL-12 secretion portends favorable implications for pegfilgrastim administration to patients with cancer, a clinical context where the induction of immune deviation would be highly undesirable.