Molecular cloning and characterization of a human metalloprotease disintegrin— a novel marker for dendritic cell differentiation

Host transcriptome response to Borrelia burgdorferi sensu lato

The host immune response to infection is a well-coordinated system of innate and adaptive immune cells working in concert to prevent the colonization and dissemination of a pathogen. While this typically leads to a beneficial outcome and the suppression of disease pathogenesis, the Lyme borreliosis bacterium, Borrelia burgdorferi sensu lato, can elicit an immune profile that leads to a deleterious state. As B. burgdorferi s.l. produces no known toxins, it is suggested that the immune and inflammatory response of the host are responsible for the manifestation of symptoms, including flu-like symptoms, musculoskeletal pain, and cognitive disorders. The past several years has seen a substantial increase in the use of microarray and sequencing technologies to investigate the transcriptome response induced by B. burgdorferi s.l., thus enabling researchers to identify key factors and pathways underlying the pathophysiology of Lyme borreliosis. In this review we present the major host transcriptional outcomes induced by the bacterium across several studies and discuss the overarching theme of the host inflammatory and immune response, and how it influences the pathology of Lyme borreliosis.

FLT3/FLT3L-mediated CD103+ dendritic cells alleviates hepatic ischemia-reperfusion injury in mice via activation of treg cells

BACKGROUND

This study was conducted to investigate the protective effect of Fms-like tyrosine kinase 3 (FLT3)/FLT3 ligand (FLT3L)-dependent CD103⁺ dendritic cells (DCs) on hepatic ischemia-reperfusion injury (IRI).

METHODS

A mouse model of hepatic IRI and cellular model following hypoxia-reperfusion (H/R) treatment were established. Peripheral blood and liver tissues were obtained and analyzed by flow cytometer in terms of percentage of CD103⁺DCs and regulatory T (Treg) cells. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were determined to assess liver function. Moreover, pro-inflammatory cytokines levels including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were measured using enzyme-linked immunosorbent assay (ELISA). The histological morphology of liver tissues was examined with hematoxylin and eosin (HE) staining. The apoptosis was detected by terminal deoxynucleotidyl transferase (TdT) dUTP Nick End Labeling (TUNEL) assay. Treg-associated cytokines transforming growth factor (TGF)-β and IL-10 expressions were measured using quantitative real time polymerase chain reaction (qRT-PCR).

RESULTS

CD103⁺ DCs were significantly decreased in peripheral blood and liver tissues of mouse model of hepatic IRI. In vivo experiments indicated that CD103⁺ DCs infusion ameliorated IRI-induced liver damage and Treg inhibition. Further investigations demonstrated that FLT3/FLT3L-dependent CD103⁺ DCs suppressed hepatocyte apoptosis via activation of Treg cells in vitro.

CONCLUSION

FLT3/FLT3L-induced CD103⁺ DCs alleviated hepatic IRI through activating Treg cells.

A Disintegrin and Metalloprotease (ADAM): Historical Overview of Their Functions

Since the discovery of the first disintegrin protein from snake venom and the following identification of a mammalian membrane-anchored metalloprotease-disintegrin implicated in fertilization, almost three decades of studies have identified additional members of these families and several biochemical mechanisms regulating their expression and activity in the cell. Most importantly, new in vivo functions have been recognized for these proteins including cell partitioning during development, modulation of inflammatory reactions, and development of cancers. In this review, we will overview the a disintegrin and metalloprotease (ADAM) family of proteases highlighting some of the major research achievements in the analysis of ADAMs' function that have underscored the importance of these proteins in physiological and pathological processes over the years.

Molecular mechanism of cell death induced by king cobra (Ophiophagus hannah) venom l-amino acid oxidase

Snake venom LAAOs have been reported to exhibit a wide range of pharmacological activities, including cytotoxic, edema-inducing, platelet aggregation-inducing/platelet aggregation-inhibiting, bactericidal and antiviral activities. A heat-stable form of l-amino acid oxidase isolated from king cobra (Ophiophagus hannah) venom (OH-LAAO) has been shown to exhibit very potent cytotoxicity against human tumorigenic cells but not in their non-tumorigenic counterparts, and the cytotoxicity was due to the apoptosis-inducing effect of the enzyme. In this work, the molecular mechanism of cell death induced by OH-LAAO was investigated. The enzyme exerts its apoptosis-inducing effect presumably via both intrinsic and extrinsic pathways as suggested by the increase in caspase-8 and -9 activities. Oligonucleotide microarray analysis showed that the expression of a total of 178 genes was significantly altered as a result of oxidative stress induced by the hydrogen peroxide generated by the enzyme. Of the 178 genes, at least 27 genes are involved in apoptosis and cell death. These alterations of gene expression was presumably caused by the direct cytotoxic effect of H2O2 generated during the enzymatic reaction, as well as the non-specific oxidative modifications of signaling molecules that eventually lead to apoptosis and cell death. The very substantial up-regulation of cytochrome P450 genes may also contribute to the potent cytotoxic action of OH-LAAO by producing excessive reactive oxygen species (ROS). In conclusion, the potent apoptosis inducing activity of OH-LAAO was likely due to the direct cytotoxic effect of H2O2 generated during the enzymatic reaction, as well as the non-specific oxidation of signalling molecules.

Dynamic change of Adamalysin 19 (ADAM19) in human placentas and its effects on cell invasion and adhesion in human trophoblastic cells

Human ADAM19 is a recently identified member of the ADAM family. It is highly expressed in human placentas, but its dynamic change and function at the human feto-maternal interface during placentation remain to be elucidated. In this present study, the spatial and temporal expression and cellular localization of ADAM19 in normal human placentas were first demonstrated, and the effects of ADAM19 on trophoblast cell adhesion and invasion were further investigated by using a human choriocarcinoma cell line (JEG-3) as an in vitro model. The data demonstrated that ADAM19 was widely distributed in villous cytotrophoblast cells, syncytiotrophoblast cells, column trophoblasts, and villous capillary endothelial cells during early pregnancy. The mRNA and protein level of ADAM19 in placentas was high at gestational weeks 8-9, but diminished significantly at mid- and term pregnancy. In JEG-3 cells, the overexpression of ADAM19 led to diminished cell invasion, as well as increases in cell adhesiveness and the expression of E-cadherin, with no changes in beta-catenin expression observed. These data indicate that ADAM19 may participate in the coordinated regulation of human trophoblast cell behaviors during the process of placentation.

In vitro allergen challenge of peripheral blood induces differential gene expression in mononuclear cells of asthmatic patients: inhibition of cytosolic phospholipase A2alpha overcomes the asthma-associated response

BACKGROUND

Existing treatments for asthma are not effective in all patients and disease exacerbations are common, highlighting the need for increased understanding of disease mechanisms and novel treatment strategies. The leukotriene pathway including the enzyme responsible for arachidonic acid release from cellular phospholipids, cPLA(2)alpha, is a major contributor to asthmatic responses and an attractive target in asthma therapies.

OBJECTIVE

The study reported here investigates (a) the differential effects of in vitro exposure of peripheral blood mononuclear cells (PBMCs) to allergen between asthma and healthy subjects, and (b) the contribution of cPLA(2)alpha to these differences in gene expression.

METHODS

In vitro responses of asthma (N=26) and healthy (N=11) subject PBMC samples to allergen stimulation in the presence and absence of cPLA(2)alpha inhibition or 5-lipoxygenase inhibition were compared at the gene expression level using oligonucleotide arrays and at the protein level using ELISA.

RESULTS

Subject samples within both asthma and healthy groups showed allergen-dependent cytokine production and allergen-dependent gene expression changes, although transcriptional profiling identified 153 genes that were modulated significantly differently by allergen between asthma and healthy subjects. Among these were genes previously associated with asthma, but the majority (about 80%) have not previously been associated with asthma.

CONCLUSIONS

Transcriptional profiling elucidated novel gene expression differences between the asthmatic and healthy subject samples. Although 5-lipoxygenase inhibition did not significantly affect allergen-modulated gene expression, the inhibition of cPLA(2)alpha activity affected many of the allergen-dependent, asthma-associated gene expression changes.

Expression of cytokine-associated genes in dendritic cells (DCs): comparison between adult peripheral blood- and umbilical cord blood-derived DCs by cDNA microarray

OBJECTIVE

The expression of cytokine-associated genes in dendritic cells (DCs) derived from umbilical cord blood (UCB) and adult peripheral blood (APB) was comprehensively compared in order to elucidate the difference in DC function between newborns and adults.

STUDY DESIGN

Immature DCs were obtained from UCB and APB of healthy human donors. Several cytokines were added to generate mature DCs. Gene expression was compared using cDNA microarray containing 553 cytokine-associated genes. Eleven genes with differential expression were selected and determined their expression levels in DCs by quantitative real-time RT-PCR.

RESULTS

The expression of the Th1 response-related genes (IL-12B and IL-18) and chemokine genes (CXCL9, CXCL13, CCL18 and CCL24) was significantly lower in UCB-DCs than in APB-DC in both maturation states. On the other hand, calgranulins A and B, which are speculated to induce immune tolerance, showed higher expression in UCB-DCs. The expression of cell cycle-related genes (CDC2 and cyclin B1) was significantly higher in UCB-DCs than in APB-DCs, and immature UCB-DCs proliferated more rapidly than immature APB-DCs.

CONCLUSION

The expression of genes related to immune responses was significantly different between UCB- and APB-DCs, which may cause a decreased DC-mediated immunity and an increased susceptibility to infection in newborns.

ADAM proteins in the brain

ADAM proteins are a family of metalloproteinases with a disintegrin domain. They have proteolytic as well as adhesive functions and can be involved in cell fusion events. Some ADAM proteins are expressed in a highly tissue restricted fashion, whereas others are expressed quite ubiquitously. In the brain, ADAM proteins have a role in neural development, axon guidance and inflammatory responses. Although there may be some functional overlap, homozygous deletion of some ADAM genes in mice can have fatal consequences. The expression and possible role of ADAM proteins in the brain will be discussed.

ADAM19 expression in human nephrogenesis and renal disease: Associations with clinical and structural deterioration

ADAM19, an enzyme from the ADAM (a disintegrin and metalloproteinase) family, is involved in various cell-cell and cell-matrix interactions. It can cleave epidermal growth factor (EGF)-like growth factors, such as heparin-binding (HB)-EGF and neuregulin (NRG), from the cell membrane. ADAM-mediated EGF receptor activation is crucial in the development of renal pathology. Based on these data, we studied ADAM19 in human nephrogenesis and renal disease. We collected 20 fetal kidneys and 56 biopsies from patients with various renal diseases. The unaffected part of kidneys from eight patients with renal cell carcinoma served as control. RNA in situ hybridization revealed widespread ADAM19 mRNA expression in the nephrogenic zone of human fetal kidneys. Normal human kidneys showed constitutive ADAM19 expression in distal tubules and endothelial cells, whereas proximal tubules were negative. In renal disease, ADAM19 was de novo expressed in proximal tubules and glomerular mesangium and upregulated in distal tubules and endothelial cells. ADAM19 colocalized with tubular and interstitial NRG, however, not with HB-EGF. Independent of renal disorder, mesangial ADAM19 expression was associated with glomerular damage as assessed by mesangial matrix expansion, focal glomerulosclerosis, and glomerular macrophage influx (all P<0.001). ADAM19 in proximal tubules and in peritubular capillaries was associated with interstitial fibrosis (P<0.05). Finally, increasing tubular ADAM19 was associated with declining renal function (P<0.05). The abundant ADAM19 expression during nephrogenesis points to a role in growth promotion and regulation. The high ADAM19 expression in renal disease suggests involvement in profibrotic and proinflammatory processes leading to renal deterioration.

Upregulation of ADAM19 in chronic allograft nephropathy

ADAM19 (a disintegrin and metalloproteinase 19) is involved in cell-cell and cell-matrix interactions and tumor necrosis factor (TNF)-alpha shedding. We studied ADAM19 in chronic allograft nephropathy (CAN) nephrectomies and in normal human kidneys. Reverse transcriptase (RT) PCR revealed an upregulation of ADAM19 mRNA in CAN when compared with control kidneys (p = 0.002). Using RNA in situ hybridization (ISH), we detected moderate ADAM19 mRNA expression in vascular smooth muscle cells (SMCs) and distal tubuli of control kidneys. In CAN, massive ADAM19 expression was detected in SMCs, distal tubuli, glomerular sclerotic lesions and inflammatory CD4+ cells. To determine whether ADAM19 is specifically related to CAN, we studied transplant biopsies with and without CAN, acute rejection and non-transplant-related kidney diseases: interstitial fibrosis (IF), interstitial atrophy, glomerular fibrosis and interstitial inflammation. In various renal structures, ADAM19 mRNA was significantly higher in CAN when compared with renal allografts without CAN or acute rejection. ADAM19 expression in renal endothelium was significantly higher in acute rejection when compared with renal allografts without CAN. When compared to CAN, ADAM19 was expressed to a similar extent in non-transplant-related interstitial and glomerular fibrosis, interstitial atrophy and inflammation. Although these observational data do not establish a cause and effect relationship, ADAM19 may have a modulatory role in the dysfunctional renal allograft state.

Epigenetic regulation of the dendritic cell-marker gene ADAM19

Human ADAM19 (MADDAM) is a molecular marker for human dendritic cells and not expressed in macrophages. To investigate its cell-type-specific expression, we defined the transcriptional start site and the proximal promoter. Sequence analysis of the promoter revealed putative binding sites for several transcription factors including Sp1, Sp3, NF-kappaB, and VDR. A minimal promoter construct of 150 bp showed little difference in reporter activity between macrophages and dendritic cells. Transfection of monocytic THP-1 with the 150-bp fragment also resulted in significant reporter activity, despite the lack of endogenous MADDAM expression. TSA, a known inhibitor of histone deacetylation, led to a dose-dependent induction of MADDAM mRNA in THP-1. ChIP assays demonstrated high levels of acetylated histone H3 in the proximal promoter region of the MADDAM gene in TSA-treated THP-1 cells and dendritic cells as compared to macrophages, indicating an important role of histone acetylation in the regulation of the MADDAM gene.

Expression of adamalysin 19/ADAM19 in the endometrium and placenta of rhesus monkey (Macaca mulatta) during early pregnancy

A disintegrin and metalloproteinase (ADAM) 19 may contribute to multiple processes including proteolysis, adhesion and intracellular signalling. These processes are also critical for embryo implantation. The aim of this study was to investigate the spatio-temporal expression of the ADAM19 in rhesus monkey uteri on days 12, 18 and 26 of pregnancy. The results showed that in the cloned monkey 346 bp ADAM19 gene fragment and 114 amino acid residues were 98 and 100% identical to those of human homologues, respectively. In-situ hybridization confirmed that the ADAM19 mRNA was located in the luminal and glandular epithelium on day 12 of pregnancy. On day 18 of pregnancy, strong signals of the ADAM19 mRNA were detected in the placental villi, trophoblastic column and glandular epithelium near the myometrium. Moderate expression of the ADAM19 mRNA was seen in the trophoblastic shell and stromal cells. The placental villi and trophoblastic column expressed abundant ADAM19 mRNA, and ADAM19 transcripts were also detected in the trophoblastic shell and fetal-maternal border on day 26 of pregnancy. The expression pattern of the ADAM19 protein was similar to its transcript, but signals for the ADAM19 protein in the stromal cells and trophoblastic shell increased more than its mRNA on day 18 of pregnancy. Statistical analysis demonstrated that the expression level of ADAM19 significantly increased on day 18 of pregnancy. These data suggest that the ADAM19 may be involved in the key processes of glandular secretion, trophoblast invasion and degradation of extracellular matrix during early pregnancy.

Targeting dendritic cells for priming cellular immune responses

The cardinal role of dendritic cells (DC) in priming adaptive immunity and in orchestrating immune responses against all classes of pathogens and also against tumors is well established. Their unique potential both to maintain self-tolerance and to initiate protective immune responses against foreign and/or dangerous structures is based on the functional diversity and flexibility of these cells. Tissue DC lining antigenic portals such as mucosal surfaces and the skin are specialized to take up a wide array of compounds including proteins, lipids, carbohydrates, glycoproteins, glycolipids and oligonucleotides, particles carrying such structures and apoptotic or necrotic cells. This process is facilitated by specialized receptors with high endocytic capacity, which provides potential targets for delivering designed molecules. The best route for targeting B- and/or T cell epitopes, however, is still the subject of intense investigation. Immature DC, which reside in various tissues, can be activated by pathogens, stress and inflammation or modified metabolic products, which induce mobilization of cells to draining lymph nodes where they act as highly potent professional antigen presenting cells. This is brought about by the ability to present their accumulated intracellular content for both CD4+ helper (Th) and CD8+ cytotoxic/cytolytic T lymphocytes (Tc/CTL). Engulfed proteins are processed intracellularly and their peptide fragments are transported to the cell surface in the context of major histocompatibility complex encoded class I and II molecules for presentation to Th cells and CTLs, respectively. The T cell priming capacity of DC, however, depends not only on antigen presentation but also on other features of DC. Human monocyte-derived DC provide an excellent tool to study the internalizing, antigen-presenting and T cell-activating functions of DC at their immature and activated differentiation states. These biological activities of DC, however, are highly dependent on their migratory potential from the peripheral non-lymphoid tissues to the lymph nodes, on the expression of adhesion molecules, which support the interaction of DC with T lymphocytes, and the cytokines secreted by DC, which polarize immune responses to Th1-mediated cellular or Th2-mediated antibody responses. These results altogether demonstrate that monocyte-derived DC are useful candidates for in vitro or in vivo targeting of antigens to induce efficient adaptive immune responses against pathogens and also against tumors.

Inverse regulation of the ADAM-family members, decysin and MADDAM/ADAM19 during monocyte differentiation

Two members of the ADAM (a disintegrin and metalloprotease)-family, MADDAM and decysin, were described as dendritic cell (DC) maturation markers. We are interested in monocyte differentiation and investigated in particular the expression pattern of both genes during the differentiation of human monocytes into DC and macrophages (MAC). Both genes are weakly expressed in freshly isolated monocytes. In immature DC decysin mRNA was absent, even after induction of the terminal differentiation of DC by CD40L or tumour necrosis factor-alpha (TNF-alpha). Only in DC maturated by lipopolysaccharide (LPS) strong signals of decysin mRNA were detected. However, MADDAM mRNA was expressed in immature DC and the expression was markedly increased after induction of the terminal DC differentiation by various stimuli. In contrast, MAC showed a high constitutive decysin mRNA expression, but expressed no MADDAM mRNA. On protein level similar results of MADDAM expression were obtained. Stimulation of MAC by LPS did not induce MADDAM mRNA expression, while decysin mRNA expression was strongly increased. Further investigations revealed that the well-known inducer of MAC differentiation, 1alpha,25-dihydroxyvitamin D3 up-regulated decysin mRNA expression during the differentiation of primary monocytes and myelomonocytic THP-1 cells into MAC. In vivo decysin mRNA expression was only detected in human colon, but not in other tissues we examined. Accordingly, isolated intestinal MAC expressed decysin mRNA. In conclusion, decysin and MADDAM mRNA expression were regulated in an opposite way during monocyte differentiation: MADDAM mRNA and protein was mainly detected in DC, whereas decysin mRNA expression was mainly found in MAC. Therefore only MADDAM, but not decysin is a suitable marker for human monocyte-derived DC.

Human ADAM33 messenger RNA expression profile and post-transcriptional regulation

We examined transcript expression and post-transcriptional regulation of human ADAM33, a recently identified asthma gene. A detailed messenger RNA (mRNA) expression profile was obtained using Northern, reverse transcription polymerase chain reaction, and in situ hybridization analyses. ADAM33 mRNA was expressed significantly in smooth muscle-containing organs, minimally in immune organs and hematopoietic cells, and highly in repairing duodenal granulation tissue. Expression was seen in asthmatic subepithelial fibroblasts and smooth muscle but not in respiratory epithelium. In all tissues, transcripts of approximately 5 kb predominated over those of approximately 3.5 kb by 2- to 5-fold. The effect of the 3' untranslated region (UTR) on ADAM33 protein expression and maturation was examined. The presence of the 3'UTR in untagged full-length constructs promoted prodomain removal, detected as mature approximately 100 kD protein by ADAM33-reactive antibodies; in its absence, maturation was 2- to 3-fold less in HEK293 cells. His-tagged and untagged constructs lacking the 3'UTR demonstrated that lack of maturation was not a result of tag-mediated effects. Minimal maturation of ADAM33 occurred in primary lung and MRC5 fibroblasts following adenoviral-mediated expression of ADAM33 lacking the 3'UTR. In contrast, prodomain removal was observed with plasmids and adenovirus encoding only the pro- and catalytic domains. Thus, the 3'UTR of ADAM33 and domains downstream of the catalytic domain regulate potential ADAM33 activity. Mechanisms of regulation of ADAM33, distinct from closely related ADAMs, thus include mRNA localization and processing and protein maturation.

Regulation of 25-hydroxyvitamin D3-1 alpha-hydroxylase and production of 1 alpha,25-dihydroxyvitamin D3 by human dendritic cells

25-Hydroxyvitamin D3-1 alpha-hydroxylase (25(OH)D3-1 alpha-hydroxylase), the key enzyme of 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) production, is expressed in monocyte-derived macrophages (MACs). Here we show for the first time constitutive expression of 25(OH)D3-1 alpha-hydroxylase in monocyte-derived dendritic cells (DCs), which was increased after stimulation with lipopolysaccharide (LPS). Accordingly, DCs showed low constitutive production of 1,25(OH)2D3, but activation by LPS increased 1,25(OH)2D3 synthesis. In addition, 25(OH)D3-1 alpha-hydroxylase expression was found in blood DCs but not in CD34+-derived DCs. Next we analyzed the functional consequences of these results. Addition of 1,25(OH)2D3 at concentrations comparable with those produced by DCs inhibited the allostimulatory potential of DCs during the early phase of DC differentiation. However, terminal differentiation decreased the responsiveness of DCs to 1,25(OH)2D3. In conclusion, DCs are able to produce 1,25(OH)2D3 especially following stimulation with LPS. Terminal maturation renders DCs unresponsive to the effects of 1,25(OH)2D3, but those cells are able to suppress the differentiation of their own precursor cells in a paracrine way through the production of 1,25(OH)2D3.

Towards determining the differentiation program of antigen-presenting dendritic cells by transcriptional profiling

Dendritic cells (DC) represent professional antigen-presenting cells that develop from hematopoietic progenitors through successive steps of differentiation. Employing DNA microarray technology, we analysed the specific changes in gene expression that occur when human progenitor cells differentiate into DC. CD34 progenitor cells were first amplified in vitro with stem cell factor (SCF), Flt3 ligand (FL), thrombopoietin and IL-6/soluble IL-6 receptor fusion protein, and cells were then induced to differentiate into DC with IL-4 and GM-CSF. DC maturation was induced by TNFalpha. Progenitor cells and DC were subjected to transcriptional profiling by DNA microarrays that represent 13000 human genes. Our analysis revealed specific changes in the expression of a large number of cell surface antigens including molecules involved in antigen uptake and processing, cell migration and antigen presentation. Genes encoding such molecules were upregulated during DC differentiation as were genes encoding cytokines, cytokine receptors, chemokines and chemokine receptors. Stem cell genes and genes related to the multilineage differentiation potential and proliferative state of progenitor cells were downregulated. Our analysis also provides information on the expression profiles of transcriptional regulators such as the NF-kappaB/rel and STAT transcription factors. Interestingly, NF-kappaB/rel factors were found to be expressed in both progenitor cells and DC at similar levels and were induced by TNFalpha. In contrast, expression of STAT factors increased during DC differentiation and their expression was virtually unaffected by TNFalpha.

Rapid establishment of dendritic cell chimerism in allogeneic hematopoietic cell transplant recipients

Regeneration of hematopoiesis after allogeneic hematopoietic cell transplantation (HCT) involves conversion of the recipient's immune system to donor type. It is likely that distinct cell lineages in the recipient reconstitute at different rates. Dendritic cells (DCs) are a subset of hematopoietic cells that function as a critical component of antigen-specific immune responses because they modulate T-cell activation, as well as induction of tolerance. Mature DCs are transferred with hematopoietic grafts and subsequently arise de novo. Little information exists about engraftment kinetics and turnover of this cell population in patients after allogeneic HCT. This study examined the kinetics of DC chimerism in patients who underwent matched sibling allogeneic HCT. T-cell, B-cell, and myelocytic and monocytic chimerism were also studied. Peripheral blood cells were analyzed at defined intervals after transplantation from 19 patients with various hematologic malignancies after treatment with myeloablative or nonmyeloablative preparatory regimens. Cell subsets were isolated before analysis of chimerism. Despite the heterogeneity of the patient population and preparatory regimens, all showed rapid and consistent development of DC chimerism. By day +14 after transplantation approximately 80% of DCs were of donor origin with steady increase to more than 95% by day +56. Earlier time points were examined in a subgroup of patients who had undergone nonmyeloablative conditioning and transplantation. These data suggest that a major proportion of blood DCs early after transplantation is donor-derived and that donor chimerism develops rapidly. This information has potential implications for manipulation of immune responses after allogeneic HCT.

Expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases define the migratory characteristics of human monocyte-derived dendritic cells

Dendritic cells (DCs) have an essential role in the initiation of immune responses as they deliver antigen/epitope and the appropriate signals to activate naïve T cells and thus start an immune response. In order to fulfil their function, DCs have to patrol different part of the body, thus migrating through the extracellular matrix to sample the local 'antigenic' environment. In the present study, we have investigated which enzymes might be involved in this process using the Matrigel trans-well migration assay, an in vitro model of extracellular matrix migration. In this assay we analysed the migratory ability of interleukin-4 (IL-4)/granulocyte macrophage-colony-stimulating factor (GM-CSF)-derived immature DCs as well as mature DCs, induced by tumour necrosis factor-alpha (TNF-alpha) and modified vaccinia virus Ankara (MVA). The 'mature' DCs showed an increased migration through Matrigel, which was significantly inhibited by inhibitors of matrix metalloproteinases (MMP). We also observed that the dominant MMP involved in this process was MMP-9, and a concomitant decrease of the endogenous tissue inhibitors of metalloproteinases (TIMP)-1 and TIMP-2 was also observed. Collectively these data suggest that the balance between MMP/TIMP determines the net migratory capacity of human DCs. Surprisingly, TIMP-3 was significantly increased in mature DC. Our data thus indicate that MMP and TIMP play a role in the migratory ability of human DCs. Our results also suggest that TIMP-3 expression might represent a new marker of maturation of human DCs.