Role of dendritic cells: a step forward for the hygiene hypothesis

Effect of early postnatal supplementation of newborns with probiotic strain E. coli O83:K24:H31 on allergy incidence, dendritic cells, and microbiota

Introduction

Probiotic administration seems to be a rational approach to promote maturation of the neonatal immune system. Mutual interaction of the microbiota with the host immune system is critical for the setting of appropriate immune responses including a tolerogenic one and thevmaintenance of homeostasis. On the other hand, our knowledge on the modes of actions of probiotics is still scarce.

Methods

In our study, probiotic strain Escherichia coli O83:K24:H31 (EcO83) was administered to neonates of allergic mothers (AMs; neonates with increased risk for allergy development) within 48 h after the delivery, and the impact of this early postnatal supplementation on allergy incidence and selected immune markers has been analyzed 10 years after the primary EcO83 administration.

Results

We have observed decreased allergy incidence in 10-year-old children supplemented with EcO83 (13 of 52 children were allergic) in comparison with non-supplemented children of AMs (16 of 42 children were allergic). The early postnatal EcO83 supplementation appeared to limit the allergy in the high-risk group (children of AMs) compared to that in the low-risk group (children of healthy mothers). Dendritic cells (DCs) in the peripheral blood of EcO83-supplemented children do not differ significantly in cell surface presence of CD83. The immunomodulatory capacity of EcO83 on DCs was tested in vitro as well. Both directly isolated myeloid and in vitro monocyte-derived DCs from cord blood increased CD83 expression together with interleukin (IL)-10 secretion after EcO83 stimulation. The effect of early postnatal EcO83 supplementation on the microbiota composition of 10-year-old children was characterized by next-generation sequencing, and we have not observed significant changes in the microbiota composition of EcO83-supplemented and non-supplemented children at the age of 10 years.

Conclusions

Early postnatal EcO83 supplementation appears to lower allergy incidence in children of AMs. It seems that the beneficial effect of EcO83 is mediated via modulation of DC functional capacities without impacting the microbiota composition. Larger-scale studies will be necessary to confirm these preliminary findings.

Twenty-five-year research progress in hookworm excretory/secretory products

Hookworm infection is a major public health problem that threatens about 500 million people throughout tropical areas of the world. Adult hookworms survive for many years in the host intestine, where they suck blood, causing iron deficiency anemia and malnutrition. Numerous molecules, named excretory/secretory (ES) products, are secreted by hookworm adults and/or larvae to aid in parasite survival and pathobiology. Although the molecular cloning and characterization of hookworm ES products began 25 years ago, the biological role and molecular nature of many of them are still unclear. Hookworm ES products, with distinct structures and functions, have been linked to many essential events in the disease pathogenesis. These events include host invasion and tissue migration, parasite nourishment and reproduction, and immune modulation. Several of these products represent promising vaccine targets for controlling hookworm disease and therapeutic targets for many inflammatory diseases. This review aims to summarize our present knowledge about hookworm ES products, including their role in parasite biology, host-parasite interactions, and as vaccine and pharmaceutical targets and to identify research gaps and future research directions in this field.

Anti-Inflammatory Activities of Pentaherbs formula and Its Influence on Gut Microbiota in Allergic Asthma

Allergic asthma is a highly prevalent airway inflammatory disease, which involves the interaction between the immune system, environmental and genetic factors. Co-relation between allergic asthma and gut microbiota upon the change of diet have been widely reported, implicating that oral intake of alternative medicines possess a potential in the management of allergic asthma. Previous clinical, in vivo, and in vitro studies have shown that the Pentaherbs formula (PHF) comprising five traditional Chinese herbal medicines Lonicerae Flos, Menthae Herba, Phellodendri Cortex, Moutan Cortex, and Atractylodis Rhizoma possesses an anti-allergic and anti-inflammatory potential through suppressing various immune effector cells. In the present study, to further investigate the anti-inflammatory activities of PHF in allergic asthma, intragastrical administration of PHF was found to reduce airway hyperresponsiveness, airway wall remodeling and goblet cells hyperplasia in an ovalbumin (OVA)-induced allergic asthma mice model. PHF also significantly suppressed pulmonary eosinophilia and asthma-related cytokines IL-4 and IL-33 in bronchoalveolar lavage (BAL) fluid. In addition, PHF modulated the splenic regulatory T cells population, up-regulated regulatory interleukin (IL)-10 in serum, altered the microbial community structure and the short chain fatty acids content in the gut of the asthmatic mice. This study sheds light on the anti-inflammatory activities of PHF on allergic asthma. It also provides novel in vivo evidence that herbal medicines can ameliorate symptoms of allergic diseases may potentially prevent the development of subsequent atopic disorder such as allergic asthma through the influence of the gut microbiota.

Cow's Milk and Immune Function in the Respiratory Tract: Potential Mechanisms

During the last decades, the world has witnessed a dramatic increase in allergy prevalence. Epidemiological evidence shows that growing up on a farm is a protective factor, which is partly explained by the consumption of raw cow’s milk. Indeed, recent studies show inverse associations between raw cow’s milk consumption in early life and asthma, hay fever, and rhinitis. A similar association of raw cow’s milk consumption with respiratory tract infections is recently found. In line with these findings, controlled studies in infants with milk components such as lactoferrin, milk fat globule membrane, and colostrum IgG have shown to reduce respiratory infections. However, for ethical reasons, it is not possible to conduct controlled studies with raw cow’s milk in infants, so formal proof is lacking to date. Because viral respiratory tract infections and aeroallergen exposure in children may be causally linked to the development of asthma, it is of interest to investigate whether cow’s milk components can modulate human immune function in the respiratory tract and via which mechanisms. Inhaled allergens and viruses trigger local immune responses in the upper airways in both nasal and oral lymphoid tissue. The components present in raw cow’s milk are able to promote a local microenvironment in which mucosal immune responses are modified and the epithelial barrier is enforced. In addition, such responses may also be triggered in the gut after exposure to allergens and viruses in the nasal cavity that become available in the GI tract after swallowing. However, these immune cells that come into contact with cow’s milk components in the gut must recirculate into the blood and home to the (upper and lower) respiratory tract to regulate immune responses locally. Expression of the tissue homing-associated markers α4β7 and CCR9 or CCR10 on lymphocytes can be influenced by vitamin A and vitamin D3, respectively. Since both vitamins are present in milk, we speculate that raw milk may influence homing of lymphocytes to the upper respiratory tract. This review focuses on potential mechanisms via which cow’s milk or its components can influence immune function in the intestine and the upper respiratory tract. Unraveling these complex mechanisms may contribute to the development of novel dietary approaches in allergy and asthma prevention.

LPS priming in early life decreases antigen uptake of dendritic cells via NO production

Immunological mechanisms of hygiene hypothesis are expected to develop a novel strategy for allergy prevention. Although a large number of studies has investigated the relation between allergies and infection, little is known about the influence of the exposure to infections on antigen uptake by dendritic cells (DCs). In this study, we examined the effect of lipopolysaccharide (LPS) priming in early life on the antigen uptake ability of DCs by using an original mouse model. LPS priming in juvenile mice decreased the migration of antigen-capturing CD11c⁺ cells in the lymph nodes, but not in aged mice. Besides, the bone marrow-derived DCs (BMDCs) from juvenile LPS-primed mice had the poor antigen uptake ability, and constitutively produced NO through the inducible nitric oxide synthase (iNOS). Interestingly, the LPS priming-induced poor antigen uptake of BMDCs was mimicked by the NO donor, and recovered by the iNOS inhibitor. Additionally, LPS priming in juvenile mice prevented the allergic reactions, but not in aged mice. Our results suggested that an exposure to infections in early life prevents allergy through the alteration of the BM cells fate that is to induce the differentiation of BM cells into inhibitory DCs such as NO-producing DCs.

Multi-target drugs to address multiple checkpoints in complex inflammatory pathologies: evolutionary cues for novel "first-in-class" anti-inflammatory drug candidates: a reviewer's perspective

Inflammation is a complex, metabolically expensive process involving multiple signaling pathways and regulatory mechanisms which have evolved over evolutionary timescale. Addressing multiple targets of inflammation holistically, in moderation, is probably a more evolutionarily viable strategy, as compared to current therapy which addresses drug targets in isolation. Polypharmacology, addressing multiple targets, is commonly used in complex ailments, suggesting the superior safety and efficacy profile of multi-target (MT) drugs. Phenotypic drug discovery, which generated successful MT and first-in-class drugs in the past, is now re-emerging. A multi-pronged approach, which modulates the evolutionarily conserved, robust and pervasive cellular mechanisms of tissue repair, with AMPK at the helm, regulating the complex metabolic/immune/redox pathways underlying inflammation, is perhaps a more viable strategy than addressing single targets in isolation. Molecules that modulate multiple molecular mechanisms of inflammation in moderation (modulating TH cells toward the anti-inflammatory phenotype, activating AMPK, stimulating Nrf2 and inhibiting NFκB) might serve as a model for a novel Darwinian "first-in-class" therapeutic category that holistically addresses immune, redox and metabolic processes associated with inflammatory repair. Such a multimodal biological activity is supported by the fact that several non-calorific pleiotropic natural products with anti-inflammatory action have been incorporated into diet (chiefly guided by the adaptive development of olfacto-gustatory preferences over evolutionary timescales) rendering such molecules, endowed with evolutionarily privileged molecular scaffolds, naturally oriented toward multiple targets.

Gut microbiota biomodulators, when the stork comes by the scalpel

The microbial communities that reside in the human gut (microbiota) and their impact on human health and disease are nowadays one of the most exciting new areas of research. A well-balanced microbial intestinal colonization in early postnatal life is necessary for the development of appropriate innate and adaptive immune responses and to establish immune homeostasis later in life. Although the composition and functional characteristics of a 'healthy' gut microbiota remain to be elucidated, perturbations in the microbial colonization of an infant's gastrointestinal tract have been associated with an increased risk of short- and long-term immunologically mediated diseases. Emerging evidence suggests that gut microbiota biomodulators, such as probiotics, prebiotics, synbiotics, and postbiotics may support disease prevention in infants who tend to have a delayed and/or aberrant initial colonization with reduced microbiota diversity (delivery by caesarean section, premature delivery, and excessive use of perinatal antibiotics). Under these dysbiosis conditions probiotics could act as 'surrogate' colonizers to prevent immune-mediated diseases. This review focuses on the influence of delivery mode on the colonization of the infant gastro-intestinal tract. In particular, it examines the manipulation of the gut microbiota composition through the use of gut microbiota biomodulators, in the management of aberrant initial gut colonization and subsequent consequences for the health of the offspring.

CD8α¯ DC is the major DC subset which mediates inhibition of allergic responses by Schistosoma infection

Our and others' previous studies have shown that Schistosoma japonicum (SJ) infection can inhibit allergic reactions. We recently reported that DCs played an important role in SJ infection-mediated inhibition of allergy, which was associated with enhanced IL-10 and T regulatory cell responses. Here, we further compared the role of CD8α(+) DC and CD8α(-) DC subsets for the inhibitory effect. We sorted CD8α(+) DC (SJCD8α(+) DC) and CD8α(-) DC (SJCD8α(-) DC) from SJ-infected mice and tested their ability to modulate allergic responses in vivo. The data showed that the adoptive transfer of SJCD8α(-) DC was much more efficient than SJCD8α(+) DC for the suppression of allergic airway eosinophilia, mucus overproduction, antigen-specific IgE responses, and Th2 cytokines (IL-4 and IL-5). More importantly, we found that the transfer of SJCD8α(-) DC, but not SJCD8α(+) DC, significantly increased IL-10 and TGF-β production following OVA exposure. As control, the transfer of DC subsets from naïve mice had no significant effect on allergic inflammation. In addition, SJCD8α-DC expressed significantly higher IL-10 but lower IL-12, CD80 and CD86 than SJCD8α(+) DC, fitting a tolerogenic phenotype. The results suggest that CD8α(-) DC is the predominant DC subset which is involved in the parasitic infection-mediated inhibition of allergic inflammation and possibly through enhancing immunomodulatory cytokine (IL-10 and TGF-β) production.

Age-related and historical changes in the clinical characteristics of sarcoidosis in Japan

BACKGROUND

National surveys conducted in Japan between 1960 and 2004 suggest a gradually increasing incidence of sarcoidosis in women >50 years old with increased involvement of the eye, skin, and heart. However, whether this involvement is due to the increased age at diagnosis is still unclear. We aimed here to identify the age-related differences in organ involvement in sarcoidosis in Japan, as well as the historical changes in clinical characteristics and the age-specific distribution of cases at diagnosis.

METHODS

We reviewed 588 consecutive Japanese patients newly diagnosed with sarcoidosis between 1974 and 2012 at Jichi Medical University Hospital. We compared organ involvement between subgroups differentiated by sex and age (<45 years; n = 275; ≥45 years; n = 313) at diagnosis and identified historical changes in the age-specific distribution in 10-year intervals.

RESULTS

Younger patients had more common involvement of extrathoracic lymph nodes, parotid/salivary gland, and liver, while older patients had more common involvement of non-lymphatic extrathoracic organs such as the eye, heart, muscle, and kidney. The age at diagnosis has consistently increased over the past four decades. The monophasic distribution in men has tended to become biphasic, and the biphasic distribution in women monophasic. Increasing trends were apparent for hypercalcemia and involvement of the gastrointestinal tract, skin, nervous system, muscle, and kidney.

CONCLUSIONS

Elderly patients at diagnosis had various extrathoracic involvement including eye, skin, and cardiac lesions. Moreover, the age at diagnosis of sarcoidosis has continued to increase in both sexes, influencing the recent trends in clinical characteristics.

Probing of a human proteome microarray with a recombinant pathogen protein reveals a novel mechanism by which hookworms suppress B-cell receptor signaling

Na-ASP-2 is an efficacious hookworm vaccine antigen. However, despite elucidation of its crystal structure and studies addressing its immunobiology, the function of Na-ASP-2 has remained elusive. We probed a 9000-protein human proteome microarray with Na-ASP-2 and showed binding to CD79A, a component of the B-cell antigen receptor complex. Na-ASP-2 bound to human B lymphocytes ex vivo and downregulated the transcription of approximately 1000 B-cell messenger RNAs (mRNAs), while only approximately 100 mRNAs were upregulated, compared with control-treated cells. The expression of a range of molecules was affected by Na-ASP-2, including factors involved in leukocyte transendothelial migration pathways and the B-cell signaling receptor pathway. Of note was the downregulated transcription of lyn and pi3k, molecules that are known to interact with CD79A and control B-cell receptor signaling processes. Together, these results highlight a previously unknown interaction between a hookworm-secreted protein and B cells, which has implications for helminth-driven immunomodulation and vaccine development. Further, the novel use of human protein microarrays to identify host-pathogen interactions, coupled with ex vivo binding studies and subsequent analyses of global gene expression in human host cells, demonstrates a new pipeline by which to explore the molecular basis of infectious diseases.

Programming of the lung by early-life infection

Many important human diseases, such as asthma, have their developmental origins in early life. Respiratory infections in particular may alter the course of asthma and may either protect against or promote the development of this disease. It is likely that the nature of the effects depends on the type and age of infection and is determined by the impact of infection on the immune and respiratory systems. Immunity in early life is plastic and can be moulded by antigen encounter, which may enhance or reinforce the asthmatic phenotype of early life, or induce protective responses. Chlamydial respiratory infections have specific effects and may increase asthma severity in early life by promoting systemic interleukin 13 responses and causing permanent changes in lung structure. Respiratory viral infections, such as those of respiratory syncytial virus and rhinovirus, promote pro-asthmatic responses in early life that contribute to the induction of asthma. By contrast, probiotics or infection or exposure to certain bacteria, such as Streptococcus pneumoniae, may have protective effects in asthma by increasing the numbers and activity of regulatory T cells. Here, we review the impact of infections on the developmental origins of asthma. Understanding these effects may lead to new therapeutic approaches for asthma that either target deleterious infections or utilize beneficial ones.

Survival of porcine fibroblasts enhanced by human FasL and dexamethasone-treated human dendritic cells in vitro

Cell-mediated and acute vascular rejections remain to be one of the primary hurdles to achieve successful xenotransplantation. Fas ligand is known to be an important molecule for the formation of 'immune-privileged' condition and dendritic cells treated with dexamethasone (Dex-DCs) acting like tolerogenic DCs (tDCs) which are known to protect transplanted cells and organs from unwanted immune responses. The present study investigated the possibility that porcine fibroblasts expressing human Fas ligand (PhF) together with human Dex-DCs could induce prolonged survival of porcine fibroblasts in vitro. PhF was collected from an ear of human Fas ligand transgenic porcine and cell-line was established by MGEM Inc. PhF labeled with CFSE co-cultured with human peripheral blood mononuclear cells (hPBMCs) were examined with respect to induction of tolerance and cell death when co-cultured with Dex-DCs for 3days. PhF induced the apoptosis in hPBMCs, especially CD4(+) T cells. Dex-DCs showed significant (P<0.05) reduction on the expression of CD80, CD86 and MHC class I/II, and the secretion of IL-12p70, TNF-α and IL-10, but increase of latency-associated peptide (LAP). Survival of PhF was significantly higher than that of WT and it was increased in the presence of Dex-DCs when compared to the other DCs (i.e.,DCs, LPS-treated DCs and LPS/Dex-treated DCs) in vitro. Survival of PhF did not change by co-culture with Dex-DCs due to apoptotic cell death of Dex-DCs. Dex-DCs reduced the death of porcine fibroblasts and, at the same time, PhF induced the apoptosis from hPBMCs, but it was not synergistic.

A fresh look at the hygiene hypothesis: how intestinal microbial exposure drives immune effector responses in atopic disease

There currently is no consensus on which immunological mechanisms can best explain the rise in atopic disease post industrialization. The hygiene hypothesis lays groundwork for our understanding of how altered microbial exposures can drive atopy; yet since its introduction increasing evidence suggests the exposure of our immune system to the intestinal microbiota plays a key role in development of atopic disease. As societal change shifts our microbial exposure, concordant shifts in the tolerant and effector functions of our immune systems give rise to more hypersensitive responses to external antigens. This is contrasted with the greater immune tolerant capabilities of individuals still living in regions with lifestyles more representative of our evolutionary history. Recent findings, buoyed by technological advances in the field, suggest a direct role for the intestinal microbiota-immune system interplay in the development of atopic disease mechanisms. Overall, harnessing current mechanistic studies for translational research into microbiota composition and function in relation to atopy have potential for the design of therapeutics that could moderate these diseases.

Characterization of the liver-draining lymph nodes in mice and their role in mounting regional immunity to HBV

The lymphatic system is important in mounting an immune response to foreign antigens and tumors in humans and animal models. The liver produces a large amount of lymph, and its lymphatic system is divided into three major components: the portal, sublobular and superficial lymphatic vessels. Despite the fact that mice are the most commonly used laboratory animals, detailed descriptions of the anatomical location and function of the lymph nodes (LNs) that drain the liver are surprisingly absent. In this study, we found that the portal and celiac LNs adjacent to mouse liver were stained with Evans blue within 5-8 min. Enhanced green fluorescence protein (EGFP)-positive cells from the liver also drained into the two aforementioned LNs. These data indicate that the portal and celiac LNs drain the mouse liver. Lymphadenectomy of the identified liver-draining LNs resulted in hepatitis B virus (HBV) persistence in immunocompetent mice compared with the sham group. In addition, the frequencies of CD8(+) T cells and dendritic cells (DCs) increased significantly in the liver-draining LNs after hydrodynamic injection of HBV plasmid. Liver-draining LN cells in HBV plasmid-injected mice also showed significant antigen-specific proliferation in response to stimulation with recombinant hepatitis B core antigen in vitro. Adoptive transfer of these cells into Rag1(-/-) mice induced a reduction in the serum concentration of hepatitis B surface antigen (HBsAg) compared to liver-draining LN cells in uninjected mice. Altogether our data characterize the liver-draining LNs and provide evidence that the liver-draining LNs induce an anti-HBV-specific immune response responsible for HBV clearance.

Immune factors in breast milk and the development of atopic disease

Breast-feeding provides protection against infections and contains numerous factors that modulate and promote the development of the infant immune system. These factors include secretory IgA, antimicrobial proteins like CD14, cytokines, and fatty acids. Studies examining the role of breast-feeding in the development of allergic disease in infants demonstrate potentially protective as well as neutral or nonprotective effects, likely due to the heterogeneity in their study design. In this overview, we explore the potential role of immune factors in the breast milk, as well as selected probiotics, in the development of allergy.

Toll-like receptor activation during cutaneous allergen sensitization blocks development of asthma through IFN-gamma-dependent mechanisms

Toll-like receptors (TLRs) are pattern-recognition receptors that have a pivotal role as primary sensors of microbial products and as initiators of innate and adaptive immune responses. We investigated the role of TLR2, TLR3, and TLR4 activation during cutaneous allergen sensitization in the modulation of allergic asthma. The results show that dermal exposure to TLR4 ligand lipopolysaccharide (LPS) or TLR2 ligand Pam3Cys suppresses asthmatic responses by reducing airway hyperreactivity, mucus production, Th2-type inflammation in the lungs, and IgE antibodies in serum in a dose-dependent manner. In contrast, TLR3 ligand Poly(I:C) did not protect the mice from asthmatic symptoms but reduced IgE and induced IgG2a in serum. LPS (especially) and Pam3Cys enhanced the activation of dermal dendritic cell (DCs) by increasing the expression of CD80 and CD86 but decreased DC numbers in draining lymph nodes at early time points. Later, these changes in DCs led to an increased number of CD8(+) T cells and enhanced the production of IFN-γ in bronchoalveolar lavage fluid. In conclusion, dermal exposure to LPS during sensitization modulates the asthmatic response by skewing the Th1/Th2 balance toward Th1 by stimulating the production of IFN-γ. These findings support the hygiene hypothesis and pinpoint the importance of dermal microbiome in the development of allergy and asthma.

The hygiene hypothesis revisited: does exposure to infectious agents protect us from allergy?

PURPOSE OF REVIEW

The increase in incidence and prevalence of allergic disease remains a mystery and cannot be explained solely by genetic factors. The hygiene hypothesis provides the strongest epidemiological explanation for the rise in allergic disease. This review evaluates the recent epidemiological and mechanistic research in the role of infectious agents in the pathogenesis of or protection from allergic disease.

RECENT FINDINGS

Recent literature has extended the epidemiological findings of the protective effect of being born and reared in a farm environment and associates an increased diversity of organisms in house-dust samples with protection from allergic disease. Furthermore, human and animal studies provide increasing evidence for the role of both the innate and adaptive immune systems, including regulatory cells, as mediators of this protective effect.

SUMMARY

There is evidence that exposure to some infectious organisms can protect from atopy, whereas other infections appear to promote allergic diseases. The timing of exposure to infection and the properties of the infectious agent, in addition to the genetic susceptibility of the host, play an important role in the future development of allergic disease.

The transcriptome of Trichuris suis--first molecular insights into a parasite with curative properties for key immune diseases of humans

BACKGROUND

Iatrogenic infection of humans with Trichuris suis (a parasitic nematode of swine) is being evaluated or promoted as a biological, curative treatment of immune diseases, such as inflammatory bowel disease (IBD) and ulcerative colitis, in humans. Although it is understood that short-term T. suis infection in people with such diseases usually induces a modified Th2-immune response, nothing is known about the molecules in the parasite that induce this response.

METHODOLOGY/PRINCIPAL FINDINGS

As a first step toward filling the gaps in our knowledge of the molecular biology of T. suis, we characterised the transcriptome of the adult stage of this nematode employing next-generation sequencing and bioinformatic techniques. A total of ∼65,000,000 reads were generated and assembled into ∼20,000 contiguous sequences ( = contigs); ∼17,000 peptides were predicted and classified based on homology searches, protein motifs and gene ontology and biological pathway mapping.

CONCLUSIONS

These analyses provided interesting insights into a number of molecular groups, particularly predicted excreted/secreted molecules (n = 1,288), likely to be involved in the parasite-host interactions, and also various molecules (n = 120) linked to chemokine, T-cell receptor and TGF-β signalling as well as leukocyte transendothelial migration and natural killer cell-mediated cytotoxicity, which are likely to be immuno-regulatory or -modulatory in the infected host. This information provides a conceptual framework within which to test the immunobiological basis for the curative effect of T. suis infection in humans against some immune diseases. Importantly, the T. suis transcriptome characterised herein provides a curated resource for detailed studies of the immuno-molecular biology of this parasite, and will underpin future genomic and proteomic explorations.

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.