Immunophenotypic and Functional Characterization of Cord Blood Dendritic Cells

Umbilical cord blood: an undervalued and underutilized resource in allogeneic hematopoietic stem cell transplant and novel cell therapy applications

PURPOSE OF REVIEW

The purpose of this review is to primarily discuss the unwarranted decline in the use of umbilical cord blood (UCB) as a source of donor hematopoietic stem cells (HSC) for hematopoietic cell transplantation (HCT) and the resulting important implications in addressing healthcare inequities, and secondly to highlight the incredible potential of UCB and related birthing tissues for the development of a broad range of therapies to treat human disease including but not limited to oncology, neurologic, cardiac, orthopedic and immunologic conditions.

RECENT FINDINGS

When current best practices are followed, unrelated donor umbilical cord blood transplant (CBT) can provide superior quality of life-related survival compared to other allogeneic HSC donor sources (sibling, matched or mismatched unrelated, and haploidentical) through decreased risks of relapse and chronic graft vs. host disease. Current best practices include improved UCB donor selection criteria with consideration of higher resolution human leukocyte antigen (HLA) typing and CD34+ cell dose, availability of newer myeloablative but reduced toxicity conditioning regimens, and rigorous supportive care in the early posttransplant period with monitoring for known complications, especially related to viral and other infections that may require intervention. Emerging best practice may include the use of ex vivo expanded single-unit CBT rather than double-unit CBT (dCBT) or 'haplo-cord' transplant, and the incorporation of posttransplant cyclophosphamide as with haploidentical transplant and/or incorporation of novel posttransplant therapies to reduce the risk of relapse, such as NK cell adoptive transfer. Novel, non-HCT uses of UCB and birthing tissue include the production of UCB-derived immune effector cell therapies such as unmodified NK cells, chimeric antigen receptor-natural killer cells and immune T-cell populations, the isolation of mesenchymal stem cells for immune modulatory treatments and derivation of induced pluripotent stem cells haplobanks for regenerative medicine development and population studies to facilitate exploration of drug development through functional genomics.

SUMMARY

The potential of allogeneic UCB for HCT and novel cell-based therapies is undervalued and underutilized. The inventory of high-quality UCB units available from public cord blood banks (CBB) should be expanding rather than contracting in order to address ongoing healthcare inequities and to maintain a valuable source of cellular starting material for cell and gene therapies and regenerative medicine approaches. The expertise in Good Manufacturing Practice-grade manufacturing provided by CBB should be supported to effectively partner with groups developing UCB for novel cell-based therapies.

Expression of Siglec-1, -3, -5 and -10 in porcine cDC1 and cDC2 subsets from blood, spleen and lymph nodes and functional capabilities of these cells

Dendritic cells are professional antigen-presenting cells that play a critical role in the development of immune responses. DCs express a variety of Siglecs on their surface, which play a regulatory role modulating their activation through interaction with sialylated structures expressed by cells or pathogens. Here, we characterized the phenotype of porcine conventional dendritic cells subsets from blood, spleen and lymph nodes, emphasizing the analysis of the expression of Siglecs. Siglec-1 was detected in type 1 cDC and, at lower levels, in type 2 cDC in the spleen, being low to negative in blood and lymph node cDC. Siglec-3 and Siglec-5 were expressed in cDC1 at lower levels than in cDC2. Porcine cDCs did not express Siglec-10. cDC2 showed a higher capacity to phagocytose microspheres and to process DQ™-OVA than cDC1, but none of these functions was affected by engagement of Siglec-3 and -5 with antibodies on blood cDC.

Induction of Antitumor Immunity by Exosomes Isolated from Cryopreserved Cord Blood Monocyte-Derived Dendritic Cells

(1) Background: Dendritic cell (DC) vaccination has shown outstanding achievements in cancer treatment, although it still has some adverse side effects. Vaccination with DC-derived exosomes has been thought to overcome the side effects of the parental DCs. (2) Method: We performed the experiments to check the ability of cryopreserved umbilical cord blood mononuclear cell-derived DCs (cryo CBMDCs) and their exosomes to prime allogeneic T cell proliferation and allogeneic peripheral blood mononuclear cell (alloPBMCs) cytotoxicity against A549 lung cancer cells. (3) Results: We found that both lung tumor cell lysate-pulsed DCs and their exosomes could induce allogeneic T cell proliferation. Moreover, alloPBMCs primed with tumor cell lysate-pulsed DCs and their exosomes have a greater cytotoxic activity against A549 cells compared to unprimed cells and cells primed with unpulsed DCs and their exosomes. (4) Conclusion: Tumor cell lysate-pulsed DCs and their exosomes should be considered to develop into a novel immunotherapeutic strategy-e.g., vaccines-for patients with lung cancer. Our results also suggested that cryo umbilical cord blood mononuclear cells source, which is a readily and available source, is effective for generation of allogeneic DCs and their exosomes will be material for vaccinating against cancer.

Immune reconstitution following hematopoietic stem cell transplantation using different stem cell sources

Introduction: Adequate immune reconstitution post-HSCT is crucial for the success of transplantation, and can be affected by both patient- and transplant-related factors. Areas covered: A systematic literature search in PubMed, Scopus, and abstracts of international congresses is performed to investigate immune recovery posttransplant. In this review, we discuss the pattern of immune recovery in the post-transplant period focusing on the impact of stem cell source (bone marrow, peripheral blood stem cells, and cord blood) on immune recovery and HSCT outcome. We examine the impact of serotherapy on immune reconstitution and the need to tailor dosing of serotherapy agents when using different stem cell sources. We discuss new techniques being used particularly with cord blood and haploidentical grafts to improve immune recovery in each scenario. Expert opinion: Cord blood T cells provide a unique CD4+ biased immune reconstitution. Initial studies using targeted serotherapy with cord grafts showed improved immune recovery with limited alloreactivity. Two competing haploidentical approaches have developed in recent years including TCRαβ/CD19 depleted grafts and post-cyclophosphamide haplo-HSCT. Both approaches have comparable survival rates with limited alloreactivity. However, delayed immune reconstitution is still an ongoing problem and could be improved by modified donor lymphocyte infusions from the same haploidentical donor.

Modulation of Immune Tolerance via Siglec-Sialic Acid Interactions

One of the key features of the immune system is its extraordinary capacity to discriminate between self and non-self and to respond accordingly. Several molecular interactions allow the induction of acquired immune responses when a foreign antigen is recognized, while others regulate the resolution of inflammation, or the induction of tolerance to self-antigens. Post-translational signatures, such as glycans that are part of proteins (glycoproteins) and lipids (glycolipids) of host cells or pathogens, are increasingly appreciated as key molecules in regulating immunity vs. tolerance. Glycans are sensed by glycan binding receptors expressed on immune cells, such as C-type lectin receptors (CLRs) and Sialic acid binding immunoglobulin type lectins (Siglecs), that respond to specific glycan signatures by triggering tolerogenic or immunogenic signaling pathways. Glycan signatures present on healthy tissue, inflamed and malignant tissue or pathogens provide signals for “self” or “non-self” recognition. In this review we will focus on sialic acids that serve as “self” molecular pattern ligands for Siglecs. We will emphasize on the function of Siglec-expressing mononuclear phagocytes as sensors for sialic acids in tissue homeostasis and describe how the sialic acid-Siglec axis is exploited by tumors and pathogens for the induction of immune tolerance. Furthermore, we highlight how the sialic acid-Siglec axis can be utilized for clinical applications to induce or inhibit immune tolerance.

Flagellin is a Th1 polarizing factor for human CD4+ T cells and induces protection in a murine neonatal vaccination model of rotavirus infection

Neonates have an increased susceptibility to infections, particularly those caused by intracellular pathogens, leading to high morbidity and mortality rates. This is partly because of a poor response of neonatal CD4⁺ T cells, leading to deficient antibody production and a low production of IFN-γ, resulting in deficient elimination of intracellular pathogens. The poor memory response of human neonates has underpinned the need for improving vaccine formulations. Molecular adjuvants that improve the response of neonatal lymphocytes, such as the ligands of toll-like receptors (TLRs), are attractive candidates. Among them, flagellin, the TLR5 ligand, is effective at very low doses; prior immunity to flagellin does not impair its adjuvant activity. Human CD4⁺ and CD8⁺ T cells express TLR5. We found that flagellin induces the expression of IFN-γ, IL-1β and IL-12 in mononuclear cells from human neonate and adult donors. When human naïve CD4⁺ T cells were activated in the presence of flagellin, there was high level of expression of IFN-γ in both neonates and adults. Furthermore, flagellin induced IFN-γ production in Th1 cells obtained from adult donors; in the Th2 population, it inhibited IL-4 cytokine production. Flagellin also promoted expression of the IFN-γ receptor in naive CD4⁺ T cells from neonates and adults. To test the adjuvant capacity of flagellin in vivo, we used a murine neonate vaccination model for infection with rotavirus, a pathogen responsible for severe diarrhea in young infants. Using the conserved VP6 antigen, we observed an 80% protection against rotavirus infection in the presence of flagellin, but only in those mice previously primed in the neonatal period. Our data suggest that flagellin could be an attractive adjuvant for achieving a Th1 response.

Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies

Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal.

Sera from patients with active systemic lupus erythematosus patients enhance the toll-like receptor 4 response in monocyte subsets

Background

Systemic Lupus Erythematosus (SLE) is an auto-immune disease whose complex pathogenesis remains unraveled. Here we aim to explore the inflammatory ability of SLE patients’ sera upon peripheral blood (PB) monocyte subsets and myeloid dendritic cells (mDCs) obtained from healthy donors.

Methods

In this study we included 11 SLE patients with active disease (ASLE), 11 with inactive disease (ISLE) and 10 healthy controls (HC). PB from healthy donors was stimulated with patients’ sera, toll-like receptor (TLR) 4 ligand – lipopolysaccharide or both. The intracellular production of TNF-α was evaluated in classical, non-classical monocytes and mDCs, using flow cytometry. TNF-α mRNA expression was assessed in all these purified cells, after sera treatment.

Results

We found that sera of SLE patients did not change spontaneous TNF-α production by monocytes or dendritic cells. However, upon stimulation of TLR4, the presence of sera from ASLE patients, but not ISLE, significantly increased the intracellular expression of TNF-α in classical and non-classical monocytes. This ability was related to titers anti-double stranded DNA antibodies in the serum. High levels of anti-TNF-α in the patients’ sera were associated with increased TNF-α expression by co-cultured mDCs. No relationship was found with the levels of a wide variety of other pro-inflammatory cytokines. A slight increase of TNF-α mRNA expression was observed in these purified cells when they were cultured only in the presence of SLE serum.

Conclusions

Our data suggest that SLE sera induce an abnormal in vitro TLR4 response in classical and non-classical monocytes, reflected by a higher TNF-α intracellular expression. These effects may be operative in the pathogenesis of SLE.

Immunology of infants through adolescents: responses to emulate for HIV vaccines

PURPOSE OF REVIEW

The major target groups for an HIV vaccine include breastfeeding infants and adolescents. Differential immune maturity in these age groups may significantly impact vaccine efficacy, and should be taken into account when developing vaccines. Here we review these differences, with an emphasis on the immune response to vaccines for HIV and other pathogens. Recommendations for potential adaptation of current HIV vaccines are also made.

RECENT FINDINGS

An effective neonatal vaccine needs to be immunogenic in the presence of maternal antibody, and must induce cytotoxic T-lymphocyte responses, neutralizing antibody responses, both systemic and mucosal. There is renewed hope in the possibility of stimulating neutralizing antibodies with HIV vaccination. DNA vaccines are promising for neonates, but will need appropriate boosting. Certain adjuvants and vector delivery systems are more suitable for neonates. Adolescents may have stronger immune responses to HIV vaccines than adults, and will also require induction of mucosal neutralizing humoral and cellular immunity.

SUMMARY

Some current HIV vaccine strategies may need adaptation for neonates and suitable product development should be accelerated. Vaccines could induce better responses in adolescents and therefore should not be discarded prematurely. Development of vaccines that have potential for these age groups is an urgent global priority.

Attenuated mRNA expression of inflammatory mediators in neonatal rat lung following lipopolysaccharide treatment

Neonates are known to exhibit increased susceptibility to bacterial and viral infections and increasing evidence demonstrates that the increased susceptibility is related to their attenuated immune response to infections. The lung is equipped with an innate defense system involving both cellular and humoral mediators. The present study was performed to characterize the expression of inflammatory mediators in the lung of neonatal rats in comparison with older animals. Rats at postnatal day 1 (P1), P21, and P70 were treated with saline or 0.25 mg/kg lipopolysaccharide (LPS) via intraperitoneal injection. Two hours later, animals were sacrificed and the transcriptional response of key inflammatory mediators and enzyme activity of myeloperoxidase (MPO) in the lung of these animals were examined. LPS-induced messenger RNA (mRNA) expression of pro-inflammatory cytokines, namely interleukin (IL)-1β, IL-6, and tumor necrosis factor-α, antiinflammatory cytokines, namely IL-10 and IL-1 receptor antagonist (IL-1ra), and chemokines, namely macrophage inflammatory protein (MIP)-1β, MIP-2, and monocyte chemotactic protein-1, in P1 lung was much reduced compared to that in P21 and P70 animals at 2 hours postinjection. These data suggest that LPS-induced transcriptional response of cytokines and chemokines was much reduced in P1 lung even though the protein levels of these genes were not ascertained and mRNA levels of these genes may not reflect their final protein levels. MPO activity in LPS-treated P1 lung was also significantly attenuated compared to that in LPS-treated P70 lung, suggesting impaired neutrophil infiltration in P1 lung at 2 hours following LPS treatment. In parallel, the baseline mRNA expression of LPS-binding protein (LBP) in P1 lung was much lower than that in P21 and P70 lungs. While the protein level of LBP was not examined and the mRNA level of LBP may not reflect its final protein level, the reduced transcriptional response of cytokines and chemokines in P1 lung at 2 hours following LPS treatment may be attributed to lower LBP expression in P1 lung as compared to P21 and P70 lungs.

Tolerogenic versus inflammatory activity of peripheral blood monocytes and dendritic cells subpopulations in systemic lupus erythematosus

Abnormalities in monocytes and in peripheral blood dendritic cells (DC) subsets have been reported in systemic lupus erythematosus (SLE). We aim to clarify the tolerogenic or inflammatory role of these cells based on ICOSL or IFN-α and chemokine mRNA expression, respectively, after cell purification. The study included 18 SLE patients with active disease (ASLE), 25 with inactive disease (ISLE), and 30 healthy controls (HG). In purified plasmacytoid DC (pDC) was observed a lower ICOSL mRNA expression in ASLE and an increase in ISLE; similarly, a lower ICOSL mRNA expression in monocytes of ALSE patients was found. However, a higher ICOSL mRNA expression was observed in ASLE compared to HG in myeloid DCs. Interestingly, clinical parameters seem to be related with ICOSL mRNA expression. Regarding the inflammatory activity it was observed in purified monocytes and CD14^−/low CD16⁺ DCs an increase of CCL2, CXCL9, and CXCL10 mRNA expression in ASLE compared to HG. In myeloid DC no differences were observed regarding chemokines, and IFN-α mRNA expression. In pDC, a higher IFN-α mRNA expression was observed in ASLE. Deviations in ICOSL, chemokine, and IFN-α mRNA expression in peripheral blood monocytes and dendritic cells subpopulations in SLE appear to be related to disease activity.

Phenotypic and functional alterations on inflammatory peripheral blood cells after acute myocardial infarction

The frequency and function of T cells, monocytes, and dendritic cell subsets were investigated in 12 patients after acute myocardial infarction (AMI)-(T0), 1 month after the episode (T1), and in 12 healthy individuals (HG). The cell characterization and the functional studies were performed by flow cytometry and by RT-PCR, after cell sorting. The most important findings at T0 moment, when compared with T1 and HG, were: a decrease in the frequency of IL-2-producing T cells; a lower frequency of TNF-α- and IL-6-producing monocytes, myeloid dendritic cells, and CD14(-/low)CD16(+)DCs; and a lower TNF-α mRNA expression, after sorting these cells. Moreover, the regulatory function of Treg cells, at T0 moment, was upregulated, based on the FoxP3, CTLA-4, and TGF-β mRNA expression increase. The majority of these phenotypic and functional alterations disappeared at T1. Our data demonstrate that AMI induces a significant change in the immune system homeostasis.

Dendritic cells in cord blood transplantation: a review

Dendritic cells (DCs) are a heterogeneous population of antigen-presenting cells derived from hematopoietic progenitors that bridge the transition between the innate and adaptive immune responses, while maintaining self-tolerance and Th1/Th2 homeostasis, by priming other cells in either an immunogenic or tolerogenic direction. Through their role in both innate and adaptive immunity, DCs play a major part in transplant engraftment and rejection and in graft-versus-host disease (GvHD). Preferentially tolerogenic or immunogenic DC subtypes offer targets for immunotherapy, to optimize transplant success rates and prolong disease-free and overall survival. Cord blood DCs are immature and preferentially tolerogenic, due to maternal-fetal tolerance, leading to better graft acceptance and immune reconstitution and explaining the lower incidence and severity of GvHD in CB transplantation, despite donor-host mismatching. Manipulation of DC maturation and cell loading with tumor-antigens can direct antitumor immunity and target minimal residual disease, as demonstrated for acute myeloid leukemia, optimizing the graft-versus-leukemia effect.

Cytokine production by monocytes, neutrophils, and dendritic cells is hampered by long-term intensive training in elite swimmers

Elite level athletes seem to be prone to illness especially during heavy training phases. The aim of this study was to investigate the influence of long term intensive training on the functional features of innate immune cells from high competitive level swimmers, particularly the production of inflammatory mediators and the possible relationship with upper respiratory symptoms (URS) occurrence. A group of 18 swimmers and 11 healthy non athletes was studied. Peripheral blood samples were collected from athletes after 36 h of resting recovery from exercise at four times during the training season and at three times from non athletes. Samples were incubated in the presence or absence of LPS and IFN-γ and the frequency of cytokine-producing cells and the amount produced per cell were evaluated by flow cytometry. In addition, plasma cortisol levels were measured and URS recorded through daily logs. The athletes, but not the controls, showed a decrease in the number of monocytes, neutrophils, and dendritic cell (DC) subsets and in the amount of IL-1β, IL-6, IL-12, TNF-α, and MIP-1β produced after stimulation, over the training season. Differences were most noticeable between the first and second blood collections (initial increase in training volume). Athlete's cortisol plasma levels partially correlated with training intensity and could help explain the reduced in vitro cell response to stimulation. Our results support the idea that long-term intensive training may affect the function of innate immune cells, reducing their capacity to respond to acute challenges, possibly contributing to an elevated risk of infection.

Functional characterization of peripheral blood dendritic cells and monocytes in systemic lupus erythematosus

With the purpose of contributing to a better knowledge of the APCs functional activity in SLE, we evaluated the distribution and functional ability to produce pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-12) of peripheral blood (PB) monocytes and DC (tDC), particularly myeloid (mDC) and CD14(-/low)CD16(+) DC subpopulations comparing them with those obtained from healthy individuals. The study was performed in 34 SLE patients with diverse disease activity scores (SLEDAI) and 13 healthy age- and sex-matched controls (NC). Our results show an overall decrease in absolute number and relative frequency of tDC in SLE patients with active disease when compared to those with inactive disease and NC, although this decrease did not seem to have an effect on the distribution of PB DC subsets. The monocytes number in SLE patients was similar to those found in NC, whereas a higher frequency of monocytes producing cytokines as well as the amount of each cytokine per cell found without stimulation was particularly observed in those patients with active disease. After stimulation, we observed a higher frequency of IL-12-producing monocytes in active SLE patients. On the other hand, we found among DCs higher frequencies of cytokine-producing CD14(-/low)CD16(+) DCs and a higher amount of cytokines produced per cell, particularly in active disease. These findings support an increased production of inflammatory cytokines by APCs in active SLE, mostly associated with alterations in CD14(-/low)CD16(+) DC subset homeostasis that might contribute to explain the dynamic role of these cells in disease pathogenesis.

Immune regulatory cells in umbilical cord blood and their potential roles in transplantation tolerance

Umbilical cord blood (UCB) is a source of primitive hematopoietic stem (HSC) and progenitor cells, that served as an alternative to bone marrow (BM) for effective transplantation therapy. Success of HSC transplantation (HSCT) is limited in part by graft-versus-host disease (GVHD), graft rejection and delayed immune reconstitution, which all relate to immunological complications. GVHD after UCB transplantation is lower compared to that of BM HSCT. This may relate to the tolerogenic nature of T cells, mononuclear cells (MNCs) and especially immune regulatory cells existing in UCB. UCB contains limiting numbers of HSC or CD34(+) cell dose for adult patients resulting in delayed engraftment after UCB transplantation (UCBT). This needs to be improved for optimal transplantation outcomes. Approaches have been undertaken to promote HSC engraftment, including co-infusion of multiple units of UCB cells. These new methods however added additional immunological complications. Herein, we describe current knowledge on features of UCB immune cells, including regulatory T cells (Tregs) and mesenchymal stem/stromal cells (MSCs) and their potential future usage to reduce GVHD.

Cord blood nucleated cells induce delayed T cell alloreactivity

Cord blood (CB) mononuclear cells (MNCs) can be transplanted in HLA mismatched recipients with limited graft rejection or graft-versus-host disease (GVHD). Previous studies have shown that naive T cells and hyporesponsive dendritic cells are largely represented in CB. Data presented here demonstrate that CB MNCs are unable to stimulate allogeneic T cell proliferative or cytotoxic responses in standard in vitro assays. However, a suppressive effect of CB MNCs was ruled out because purified CD34(+) cells or CD14(+) monocytes stimulated T cell responses that were not inhibited by add-back of CB MNCs. The lack of antigen-presenting cell (APC) activity of CB MNCs in primary mixed lymphocyte culture (MLC) did not induce allogeneic T cell anergy. In fact, rechallenge of T cells with CB CD34(+) cells, or immature monocyte-derived dendritic cells (iMo-DCs) in secondary MLC induced potent T cell proliferative responses. A delayed APC activity of CB MNCs was observed after stimulation with irradiated allogeneic T cells for 6 days, likely because of the upregulation of CD86 and HLA-DR on CB cells. Cytotoxic lymphocytes (CTL) were generated after stimulation of blood T cells with CB MNCs for 4 weeks or CB-derived iMo-DCs for 1 week. Concomitant stimulation of T cells with CB iMo-DC obtained from 2 CB units resulted in the generation of CTLs specific for each CB, independently of the CB:CB cell ratio. These data suggest that the APC activity of CB cells possibly increases posttransplant, and may contribute to delayed graft rejection and/or acute and chronic GVHD.

Effect of intrauterine HIV-1 exposure on the frequency and function of uninfected newborns' dendritic cells

Immaturity of the neonatal immune system is considered an underlying factor for enhanced severity of infections in newborns. Functional defects of neonatal antigen-presenting cells lead to defective T-cell responses. T cells from uninfected neonates exposed in utero to HIV-1 (EU) exhibit phenotypic and functional alterations; however, the function of their circulating dendritic cells (DCs) has not been characterized. We hypothesized that an HIV-1-infected maternal environment may influence the infants' DC number, phenotype and function. EU exhibited a higher percentage of myeloid DCs (mDCs) than unexposed neonates, although this frequency remained lower than that observed in adults. Plasmacytoid DC (pDC) frequencies were similar in all groups, although both groups of infants tended to have lower frequencies than adults. After LPS stimulation, mDCs from EU up-regulated CD80, CD86 and B7-H1, whereas mDCs from unexposed infants upregulated B7-H1, but not CD80/CD86, and adult mDCs up-regulated mainly CD80 and CD86. IFN-alpha production was similar in all groups, indicating a normal pDC function. Therefore, in utero exposure to HIV-1 induces quantitative and qualitative changes in neonatal DCs, particularly in mDCs, which might be associated with alterations observed in T cells from these EU.

The phenotypical and functional characteristics of cord blood monocytes and CD14(-/low)/CD16(+) dendritic cells can be relevant to the development of cellular immune responses after transplantation

Umbilical cord blood (UCB) has been used as an alternative source of haematopoietic progenitors for transplantation presenting advantages over bone marrow (BM) that are related with known shortages of newborns' immune system at adaptive and innate levels. Using flow cytometry, we studied the expression of Toll-like receptors (TLRs) and chemokine receptors (CKRs) and the production of pro-inflammatory cytokines by monocytes and CD14(-/low)/CD16(+)DCs from peripheral blood (PB; n=10), and umbilical cord blood (UCB; n=10). CKRs and cytokines were studied before and after stimulation of cells with LPS plus IFN-gamma. We also identified the two populations in normal bone marrow samples (BM; n=5). BM presented lower frequencies of both studied populations when compared to UCB and PB. CD14(-/low)/CD16(+)DCs presented a pattern of TLR expression different from mature monocytes reflecting distinct functions for these two populations. UCB cells presented reduced expression of TLR-4 and lower capability to produce cytokines prior stimulation. The populations studied presented different patterns of CKR expression reflecting distinct migratory pathways. Moreover, UCB cells presented higher expressions of CXCR4 and CCR7 that may be involved in immune system maturation and stem cell homing. Monocytes and CD14(-/low)/CD16(+)DCs present functional and phenotypical characteristics that may contribute to the lower incidence and severity of GVHD.

Dendritic cell vaccination

There has been a surge of interest in the use of dendritic cell (DC) vaccination as cellular immunotherapy for numerous cancers. Despite some encouraging results, this therapeutic modality is far from being considered as a therapy for cancer. This review will first discuss preclinical DC vaccination in murine models of cancer, with an emphasis on comparative studies investigating different methods of antigen priming. We will then comment on the various murine DC subsets and how these relate to human DC preparations used for clinical studies. Finally, the methodology used to generate human DCs and some recent clinical trials in several cancers are reviewed.

Defective antigen-presenting cell function in human neonates

Immaturity of the immune system has been suggested as an underlying factor for the high rate of morbidity and mortality from infections in newborns. Functional impairment of neonatal T cells is frequently quoted as the main underlying mechanism for such immaturity. However, recent studies suggest that neonatal antigen-presenting cells (APCs) also exhibit functional alterations, which could lead to secondary defects of adaptive T-cell responses. In this review, we summarize what is known on the functionality of APC at birth and during early childhood. Compared to adults, neonatal APCs display markers of immaturity and produce low levels of cytokines. Multiple factors could be involved in neonatal APC alteration, such as intrinsic immaturity, defective interaction between APCs and T cells and regulatory T-cell-mediated inhibition. Characterization of the relative contribution of each mechanism is clearly needed to better understand the functional capability of the neonatal immune system.

The link between bronchiolitis and asthma

Bronchiolitis and asthma are common wheezing illnesses of childhood. Respiratory syncytial virus is the main causative agent of Bronchiolitis. Rhinovirus is the most common trigger of exacerbations of asthma, but also has been detected increasingly in doing children with Bronchiolitis. Reportedly, childhood asthma develops in 40% of children with a history of Bronchiolitis. No convincing link has been reported between Bronchiolitis and development of atopy, although atopy generally is regarded as the main risk factor for chronic asthma. This article focuses on the association between bronchiolitis and the development of asthma. The authors address the question how respiratory syncytial virus and rhinovirus infections in young children, together with genetics and immunologic immaturity, may contribute to the development of asthma.

Dendritic cells in allogeneic hematopoietic stem cell transplantation

In allogeneic hematopoietic stem cell transplantation (SCT), dendritic cells (DCs) as the most potent antigen-presenting cells play a central role in the development of acute and chronic graft-vs-host disease (GVHD), in graft-vs-leukemia or -malignancy reactions and in fighting infectious complications. Functional maturity and distribution of DC sub-types (DC1 and DC2) differ between the different stem cell sources used (bone marrow, granulocyte colony-stimulating factor-mobilised peripheral blood and cord blood) resulting in various rates of graft-vs-host disease and graft-vs-leukemia activity. Although DC recovery following stem cell transplantation is prompt, graft-vs-host disease and the use of immunosuppressive drugs result in qualitative and quantitative disturbances in DC homeostasis and have been observed for up to 1 year after transplantation. Complete donor DC chimerism seems to be a pre-requisite for the development of chronic GVHD and for graft-vs-leukemia activity, at least following reduced-intensity transplants, although in the early phase of acute graft-vs-host disease the presence of host antigen-presenting cells is essential. Preliminary data show promising results with DC-based immunotherapy for treatment of viral and fungal infections and of leukemic relapse following allogeneic stem cell transplantation. More information on the mechanisms and interactions between dendritic cells and regulatory T cells is needed for DC vaccination concepts for modulation of graft-vs-host disease.

Activated human umbilical cord blood dendritic cells kill tumor cells without damaging normal hematological progenitor cells

Apart from their role as antigen presenting cells, human peripheral blood monocyte and CD34+ cell-derived dendritic cells (DC), have been demonstrated to exert cytotoxicity against some tumor cells, and their tumoricidal activity can be enhanced by some stimili. However, there have been no reports concerning the tumoricidal activity of human cord blood dendritic cells (CBDC). In this article, we report that human cord blood monocyte-derived DC acquire the ability to kill hematological tumor cells, after activation with lipopolysaccharide (LPS) or gamma-interferon (IFN-gamma), associated with the enhanced TNF-alpha-related apoptosis-inducing ligand (TRAIL) expression in CBDC cytoplasm. The CD14-positive cells collected from cord blood were induced to CBDC in vitro. After activation with IFN-gamma for 12 h, CBDC exhibited cytotoxicity against HL60 and Jurkat cells, while activation with LPS induced cytotoxicity against Daudi and Jurkat cells. However, both LPS- and IFN-gamma-stimulated CBDC showed no cytotoxic activity against normal CD14-negative cord blood mononuclear cells. The formation of umbilical cord hematopoietic progenitor colonies, identified as burst-forming unit-erythroid and colony-forming unit granulocyte-macrophage, was not inhibited by stimulated or unstimulated CBDC. IFN-gamma or LPS stimulation enhanced intracellular but not cellular surface TRAIL, and neither intracellular nor cellular surface tumor necrosing factor-alpha and Fas Ligand as analyzed by flow cytometry. Our results show that activated CBDC can serve as cytotoxic cells against hematological tumor cells without damaging the normal hematopoietic progenitor cells.