The porcine skin has striking similarities to the human skin in terms of general structure, thickness, hair follicle content, pigmentation, collagen and lipid composition. This has been the basis for numerous studies using the pig as a model for wound healing, transdermal delivery, dermal toxicology, radiation and UVB effects. Considering that the skin also represents an immune organ of utmost importance for health, immune cells present in the skin of the pig will be reviewed. The focus of this review is on dendritic cells, which play a central role in the skin immune system as they serve as sentinels in the skin, which offers a large surface area exposed to the environment. Based on a literature review and original data we propose a classification of porcine dendritic cell subsets in the skin corresponding to the subsets described in the human skin. The equivalent of the human CD141(+) DC subset is CD1a(-)CD4(-)CD172a(-)CADM1(high), that of the CD1c(+) subset is CD1a(+)CD4(-)CD172a(+)CADM1(+/low), and porcine plasmacytoid dendritic cells are CD1a(-)CD4(+)CD172a(+)CADM1(-). CD209 and CD14 could represent markers of inflammatory monocyte-derived cells, either dendritic cells or macrophages. Future studies for example using transriptomic analysis of sorted populations are required to confirm the identity of these cells.

Endosialin (tumor endothelial marker 1) is expressed preferentially by tumor endothelial cells but not by normal endothelium. Its protein domain architecture is homologous to that of CD93 and thrombomodulin (CD141), suggesting a similar function in mediating cell-cell interactions. The aim of this study was to investigate the expression pattern of endosialin in human brain tumors in a bid to decipher its contribution to tumor angiogenesis. We generated an antibody specifically recognizing human endosialin and used it to study endosialin expression in 30 human brain tumor specimens by immunoblotting and immunohistochemistry. Twenty of 30 tumors expressed endosialin in a heterogeneous manner. The largest proportion of endosialin-expressing tumors was found in highly invasive glioblastoma multiforme, anaplastic astrocytomas, and metastatic carcinomas. Endosialin was localized to the endothelium of small and large vessels strongly stained for CD31 and was also expressed by Thy-1-positive fibroblast-like cells close to the meninges and alpha-smooth muscle actin-positive cells in some vessels. Endosialin colocalized with thrombomodulin, suggesting the proteins may have complementary functions in tumor progression.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in the world. Immunological analysis of the tumor microenvironment (immunoscore) shows great promise for improved prognosis and prediction of response to immunotherapy. However, the exact immune cell composition in NSCLC remains unclear. Here, we used flow cytometry to characterize the immune infiltrate in NSCLC tumors, non-cancerous lung tissue, regional lymph node, and blood. The cellular identity of >95% of all CD45⁺ immune cells was determined. Thirteen distinct immune cell types were identified in NSCLC tumors. T cells dominated the lung cancer landscape (on average 47% of all CD45⁺ immune cells). CD4⁺ T cells were the most abundant T cell population (26%), closely followed by CD8⁺ T cells (22%). Double negative CD4^-CD8^- T cells represented a small fraction (1.4%). CD19⁺ B cells were the second most common immune cell type in NSCLC tumors (16%), and four different B cell sub-populations were identified. Macrophages and natural killer (NK) cells composed 4.7 and 4.5% of the immune cell infiltrate, respectively. Three types of dendritic cells (DCs) were identified (plasmacytoid DCs, CD1c⁺ DCs, and CD141⁺ DCs) which together represented 2.1% of all immune cells. Among granulocytes, neutrophils were frequent (8.6%) with a high patient-to-patient variability, while mast cells (1.4%), basophils (0.4%), and eosinophils (0.3%) were less common. Across the cohort of patients, only B cells showed a significantly higher representation in NSCLC tumors compared to the distal lung. In contrast, the percentages of macrophages and NK cells were lower in tumors than in non-cancerous lung tissue. Furthermore, the fraction of macrophages with high HLA-DR expression levels was higher in NSCLC tumors relative to distal lung tissue. To make the method readily accessible, antibody panels and flow cytometry gating strategy used to identify the various immune cells are described in detail. This work should represent a useful resource for the immunomonitoring of patients with NSCLC.

Targeting antigens to cross-presenting dendritic cells (DCs) is a promising method for enhancing CD8(+) T-cell responses. However, expression patterns of surface receptors often vary between species, making it difficult to relate observations in mice to other animals. Recent studies have indicated that the chemokine receptor Xcr1 is selectively expressed on cross-presenting murine CD8α(+) DCs, and that the expression is conserved on homologous DC subsets in humans (CD141(+) DCs), sheep (CD26(+) DCs), and macaques (CADM1(+) DCs). We therefore tested if targeting antigens to Xcr1 on cross-presenting DCs using antigen fused to Xcl1, the only known ligand for Xcr1, could enhance immune responses. Bivalent Xcl1 fused to model antigens specifically bound CD8α(+) DCs and increased proliferation of antigen-specific T cells. DNA vaccines encoding dimeric Xcl1-hemagglutinin (HA) fusion proteins induced cytotoxic CD8(+) T-cell responses, and mediated full protection against a lethal challenge with influenza A virus. In addition to enhanced CD8(+) T-cell responses, targeting of antigen to Xcr1 induced CD4(+) Th1 responses and highly selective production of IgG2a antibodies. In conclusion, targeting of dimeric fusion vaccine molecules to CD8α(+) DCs using Xcl1 represents a novel and promising method for induction of protective CD8(+) T-cell responses.

HIV infects activated CD4⁺ T cells and induces their depletion. Progressive HIV infection leading to AIDS is fueled by chronic immune hyperactivation, mediated by inflammatory cytokines like TNFα. This has been related to intestinal epithelial damage and microbial LPS translocation into the circulation. Using 11-color flow cytometry, cell sorting, and cell culture, we investigated the numbers and TNFα production of fully defined circulating dendritic cell and monocyte populations during HIV-1 infection. In 15 viremic, untreated patients, compared with 8 treated, virologically suppressed patients or to 13 healthy blood donors, circulating CD141 (BDCA-3)⁺ and CD1c (BDCA-1)⁺ dendritic cell counts were reduced. Conversely, CD14⁺ CD16⁺⁺ monocyte counts were increased, particularly those expressing M-DC8, while classical CD14⁺⁺ CD16⁻ M-DC8⁻ monocyte numbers were unchanged. Blood mononuclear cells from viremic patients produced more TNFα in response to LPS than those from virologically suppressed patients. M-DC8⁺ monocytes were mostly responsible for this overproduction. Moreover, M-DC8⁺ monocytes differentiated in vitro from classical monocytes using M-CSF and GM-CSF, which is increased in viremic patient's plasma. This M-DC8⁺ monocyte population, which is involved in the pathogenesis of chronic inflammatory diseases like Crohn disease, might thus be considered as a major actor in the immune hyperactivation fueling HIV infection progression.

Respiratory syncytial virus (RSV) causes recurrent infections throughout life. Vaccine development may depend upon understanding the molecular basis for induction of ineffective immunity. Because dendritic cells (DCs) are critically involved in early responses to infection, their interaction with RSV may determine the immunological outcome of RSV infection. Therefore, we investigated the ability of RSV to infect and activate primary mDCs and pDCs using recombinant RSV expressing green fluorescent protein (GFP). At a multiplicity of infection of 5, initial studies demonstrated ∼6.8% of mDC1 and ∼0.9% pDCs were infected. We extended these studies to include CD1c(-)CD141(+) mDC2, finding mDC2 infected at similar frequencies as mDC1. Both infected and uninfected cells upregulated phenotypic markers of maturation. Divalent cations were required for infection and maturation, but maturation did not require viral replication. There is evidence that attachment and entry/replication processes exert distinct effects on DC activation. Cell-specific patterns of RSV-induced maturation and cytokine production were detected in mDC1, mDC2, and pDC. We also demonstrate for the first time that RSV induces significant TIMP-2 production in all DC subsets. Defining the influence of RSV on the function of selected DC subsets may improve the likelihood of achieving protective vaccine-induced immunity.

Adriamycin (ADR) is a commonly used chemotherapeutic agent that is believed to exert its effects through the generation of oxygen free radicals. We hypothesized that administration of a single dose of ADR results in endothelial nitric oxide synthase (eNOS)-dependent generation of superoxide (O2*-) and acute endothelial dysfunction. A single dose of ADR (10 mg/kg i.v.) administered to rabbits resulted in rapid attenuation of agonist-dependent responses to acetylcholine and calcium ionophore (A23187). In vitro exposure of ring segments to ADR for < 30 min resulted in O2*- generation measured by electron spin resonance (ESR) with the spin trap segments 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) that was abolished by endothelial denudation and incubation with diphenyliodonium (DPI) (10 microM) but not L-NMMA (10 microM). Brachial artery flow-mediated dilation (FMD) in patients undergoing chemotherapy with ADR was markedly attenuated after a single dose of ADR (6.5 +/- 1.0 to 2.5 +/- 1.1% (p = 0.0004, time to end of infusion 27 +/- 8 min) while endothelial-independent dilatation with nitroglycerin was unchanged (16.3 +/- 3.1 and 14.33 +/- 2.1% respectively, p = 0.36). Serum nitrite and nitrate concentrations fell from 50 +/- 6 micromol/l pre-ADR to 33 +/- 6 micromol/l post-ADR infusion (p = 0.0005) while serum concentrations of CD141 thrombomodulin and von Willebrand factor (vWF) activity remained unchanged after ADR infusion (36 +/- 13 to 52 +/- 22% ng/ml versus 3.25 +/- 0.98 to 3.01 +/- 0.91%, respectively, p = NS for pre versus post for both). Doppler indices of diastolic function (IVRT, DT and E/A ratios) were not altered in response to ADR. In conclusion, ADR administration results in rapid depletion of systemic NO* levels and attenuation of agonist-dependent responses in rabbits and flow-mediated dilation in the brachial artery of humans. ESR measurements in rabbit ring suggest an endothelial origin for radical production via flavin-containing oxido-reductases such as eNOS or NADPH cytochrome P450 reductase. These findings may have implications for cardiovascular complications noted with ADR.

Synovial sarcoma (SS) is a mesenchymal neoplasm that typically shows epithelial differentiation. SS commonly metastasizes to lung and pleura, and has also been reported as the primary in these locations. The histologic distinction of SS from mesothelioma may be difficult because of the combination of epithelioid and spindle cells, potentially shared locations, and antigenic expression. In this study the authors examined 103 well-documented SSs including 41 biphasic, 44 monophasic, and 18 poorly differentiated SSs in comparison with 23 epithelioid and seven sarcomatous mesotheliomas. Most biphasic SSs (29 of 41, 71%) had fields or foci of calretinin-positive tumor cells. The spindle cell components were more often positive (55%), whereas 14% of tumors had positive epithelial cells. The monophasic and poorly differentiated SSs commonly had foci of calretinin-positive cells (in 52% and 56% of cases respectively). In comparison, all 23 epithelioid mesotheliomas (EM) were extensively calretinin positive and seven sarcomatoid mesotheliomas were variably calretinin positive. HBME-1 positivity was similarly detected in biphasic SS and EM (100% and 87% respectively). Among the other sarcomas, two of 15 malignant peripheral nerve sheath tumors were focally calretinin positive, whereas 16 epithelioid sarcomas, 20 leiomyosarcomas, 20 gastrointestinal stromal tumors, and 20 angiosarcomas were negative. Biphasic SSs differed from mesotheliomas by their more common BerEp4 positivity (90%) whereas EMs showed focal reactivity in 13% cases. Marked CD15 reactivity was rare in both. Wilms tumor protein-1 (WT1) was not detected in SS, but was present in 12 of 17 EMs. CD141 was rare in SS, limited to spindle cell components, whereas EMs typically showed prominent membrane staining in epithelial cells. Simple epithelial keratins were present in all epithelial cells of biphasic SS and mesothelioma (keratin 7[K7], K19), but were only focal in monophasic and poorly differentiated SS. Biphasic SSs were extensively K14 positive (89% of cases), whereas epithelial and sarcomatoid mesotheliomas typically showed only scattered positive cells. The potentially shared calretinin patterns in SS and mesothelioma require the use of other markers. The discriminating features include extensive BerEp4 positivity, rarity of CD141, and lack of WT1 in SS. Global expression of K7 and K19 in mesotheliomas versus focal expression in monophasic and poorly differentiated SSs, and differential patterns of K14 expression may also be helpful.

OBJECTIVE

Extensive populations of liver immune cells detect and respond to homeostatic perturbation caused by damage, infection or malignancy. Dendritic cells (DCs) are central to these activities, governing the balance between tolerance and immunity. Most of our knowledge about human liver DCs is derived from studies on peritumoral tissue. Little is known about the phenotype and function of DCs, in particular the recently described CD141(+) subset, in healthy human liver and how this profile is altered in liver disease.

METHODS

During liver transplantation, healthy donor and diseased explant livers were perfused and hepatic mononuclear cells isolated. Dendritic cell subset frequency and phenotype were characterised in liver perfusates by flow cytometry and the function of CD141(+) DCs was evaluated by mixed lymphocyte reactions (MLRs) and measuring cytokine secretion.

RESULTS

Almost one third of liver CD11c(+) myeloid DCs (mDCs) expressed CD141 compared to <5% of circulating mDCs. Hepatic CD141(+) DCs demonstrated pro-inflammatory function in allogeneic MLRs, inducing T cell production of interferon gamma (IFN-γ) and interleukin (IL)-17. While CD123(+) plasmacytoid DCs (pDCs) and CD1c(+) mDCs were expanded in diseased liver perfusates, CD141(+) DCs were significantly depleted. Despite their depletion, CD141(+) DCs from explant livers produced markedly increased poly(I:C)-induced IFN lambda (IFN-λ) compared with donor DCs.

CONCLUSIONS

Accumulation of CD141(+) DCs in healthy liver, which are significantly depleted in liver disease, suggests differential involvement of mDC subsets in liver immunity.

We established a humanized mouse model incorporating FLT3-ligand (FLT3-L) administration after hematopoietic cell reconstitution to investigate expansion, phenotype, and function of human dendritic cells (DC). FLT3-L increased numbers of human CD141(+) DC, CD1c(+) DC, and, to a lesser extent, plasmacytoid DC (pDC) in the blood, spleen, and bone marrow of humanized mice. CD1c(+) DC and CD141(+) DC subsets were expanded to a similar degree in blood and spleen, with a bias toward expansion of the CD1c(+) DC subset in the bone marrow. Importantly, the human DC subsets generated after FLT3-L treatment of humanized mice are phenotypically and functionally similar to their human blood counterparts. CD141(+) DC in humanized mice express C-type lectin-like receptor 9A, XCR1, CADM1, and TLR3 but lack TLR4 and TLR9. They are major producers of IFN-λ in response to polyinosinic-polycytidylic acid but are similar to CD1c(+) DC in their capacity to produce IL-12p70. Although all DC subsets in humanized mice are efficient at presenting peptide to CD8(+) T cells, CD141(+) DC are superior in their capacity to cross-present protein Ag to CD8(+) T cells following activation with polyinosinic-polycytidylic acid. CD141(+) DC can be targeted in vivo following injection of Abs against human DEC-205 or C-type lectin-like receptor 9A. This model provides a feasible and practical approach to dissect the function of human CD141(+) and CD1c(+) DC and evaluate adjuvants and DC-targeting strategies in vivo.

BACKGROUND

A novel concept providing prenatally tissue engineered human autologous heart valves based on routinely obtained fetal amniotic fluid progenitors as single cell source is introduced.

RESULTS

Fetal human amniotic progenitors were isolated from routinely sampled amniotic fluid and sorted using CD133 magnetic beads. After expansion and differentiation, cell phenotypes of CD133- and CD133+ cells were analyzed by immunohistochemistry and flowcytometry. After characterization, CD133- derived cells were seeded onto heart valve leaflet scaffolds (n=18) fabricated from rapidly biodegradable polymers, conditioned in a pulse duplicator system, and subsequently coated with CD133+ derived cells. After in vitro maturation, opening and closing behavior of leaflets was investigated. Neo-tissues were analyzed by histology, immunohistochemistry, and scanning electron microscopy (SEM). Extracellular matrix (ECM) elements and cell numbers were quantified biochemically. Mechanical properties were assessed by tensile testing. CD133- derived cells demonstrated characteristics of mesenchymal progenitors expressing CD44 and CD105. Differentiated CD133+ cells showed features of functional endothelial cells by eNOS and CD141 expression. Engineered heart valve leaflets demonstrated endothelialized tissue formation with production of ECM elements (GAG 80%, HYP 5%, cell number 100% of native values). SEM showed intact endothelial surfaces. Opening and closing behavior was sufficient under half of systemic conditions.

CONCLUSIONS

The use of amniotic fluid as single cell source is a promising low-risk approach enabling the prenatal fabrication of heart valves ready to use at birth. These living replacements with the potential of growth, remodeling, and regeneration may realize the early repair of congenital malformations.

In mice, conventional and plasmacytoid dendritic cells (DCs) derive from separate hematopoietic precursors before they migrate to peripheral tissues. Moreover, two classes of conventional DCs (cDC1 and cDC2 DCs) and one class of plasmacytoid DCs (pDCs) have been shown to be transcriptionally and functionally distinct entities. In humans, these three DC subtypes can be identified using the cell surface markers CD1c (cDC2), CD141 (cDC1), and CD303 (pDCs), albeit it remains elusive whether DC functionality is mainly determined by ontogeny or the tissue microenvironment. By phenotypic and transcriptional profiling of these three DC subtypes in different human tissues derived from a large number of human individuals, we demonstrate that DC subpopulations in organs of the lymphohematopoietic system (spleen, thymus, and blood) are strongly defined by ontogeny rather than by signals from the microenvironment. In contrast, DC subsets derived from human lung or skin differed substantially, strongly arguing that DCs react toward modulatory signals from tissue microenvironments. Collectively, the data obtained in this study may serve as a major resource to guide further studies into human DC biology during homeostasis and inflammation.

Dendritic cells (DCs) play the central role in the priming of naive T cells and the differentiation of unique effector T cells. In this study, using lung tissues and blood from both humans and humanized mice, we analyzed the response of human CD1c(+) and CD141(+) DC subsets to live-attenuated influenza virus. Specifically, we analyzed the type of CD4(+) T cell immunity elicited by live-attenuated influenza virus-exposed DCs. Both DC subsets induce proliferation of allogeneic naive CD4(+) T cells with the capacity to secrete IFN-γ. However, CD141(+) DCs are uniquely able to induce the differentiation of IL-4- and IL-13-producing CD4(+) T cells. CD141(+) DCs induce IL-4- and IL-13-secreting CD4(+) T cells through OX40 ligand. Thus, CD141(+) DCs demonstrate remarkable plasticity in guiding adaptive immune responses.

Characterization of functionally distinct dendritic cell (DC) subsets in mice has fueled interest in whether analogous counterparts exist in humans. Transcriptional modules of coordinately expressed genes were used for defining shared functions between the species. Comparing modules derived from four human skin DC subsets and modules derived from the Immunological Genome Project database for all mouse DC subsets revealed that human Langerhans cells (LCs) and the mouse XCR1(+)CD8α(+)CD103(+) DCs shared the class I-mediated antigen processing and cross-presentation transcriptional modules that were not seen in mouse LCs. Furthermore, human LCs were enriched in a transcriptional signature specific to the blood cross-presenting CD141/BDCA-3(+) DCs, the proposed equivalent to mouse CD8α(+) DCs. Consistent with our analysis, LCs were highly adept at inducing primary CTL responses. Thus, our study suggests that the function of LCs may not be conserved between mouse and human and supports human LCs as an especially relevant therapeutic target.

Dendritic cells (DCs) can initiate and direct adaptive immune responses. This ability is exploitable in DC vaccination strategies, in which DCs are educated ex vivo to present tumor antigens and are administered into the patient with the aim to induce a tumor-specific immune response. DC vaccination remains a promising approach with the potential to further improve cancer immunotherapy with little or no evidence of treatment-limiting toxicity. However, evidence for objective clinical antitumor activity of DC vaccination is currently limited, hampering the clinical implementation. One possible explanation for this is that the most commonly used monocyte-derived DCs may not be the best source for DC-based immunotherapy. The novel approach to use naturally circulating DCs may be an attractive alternative. In contrast to monocyte-derived DCs, naturally circulating DCs are relatively scarce but do not require extensive culture periods. Thereby, their functional capabilities are preserved, the reproducibility of clinical applications is increased, and the cells are not dysfunctional before injection. In human blood, at least three DC subsets can be distinguished, plasmacytoid DCs, CD141⁺ and CD1c⁺ myeloid/conventional DCs, each with distinct functional characteristics. In completed clinical trials, either CD1c⁺ myeloid DCs or plasmacytoid DCs were administered and showed encouraging immunological and clinical outcomes. Currently, also the combination of CD1c⁺ myeloid and plasmacytoid DCs as well as the intratumoral use of CD1c⁺ myeloid DCs is under investigation in the clinic. Isolation and culture strategies for CD141⁺ myeloid DCs are being developed. Here, we summarize and discuss recent clinical developments and future prospects of natural DC-based immunotherapy.

The emergence of the targeted therapies for non-small cell lung carcinoma (NSCLC) has generated a need for accurate histologic subtyping of NSCLC. In this study, we assessed the utility of immunohistochemical markers that could be helpful in distinction between adenocarcinoma (ADC) and squamous cell carcinoma (SCC). We performed a battery of immunohistochemistry using tissue microarray for napsin-A, Thyroid transcription factor 1 (TTF-1), p63, cytokeratin (CK) 5/6, thrombomodulin (CD141), Epithelial-related antigen (MOC-31), carcinoembryonic antigen (CEA), Cyclooxygenase 2 (COX-2), high-molecular-weight CK (HMWCK), p27kip1 (p27), and Rb protein in 129 resected primary NSCLC with 81 ADCs and 48 SCCs and 10 metastatic ADC to the lung (primary in colon, 7 cases; stomach, 2 cases; vagina, 1 case). Cases of ADC and SCC were morphologically unequivocal and solid tumors with no definite squamous or glandular differentiation were excluded for this analysis. Napsin-A and TTF-1 were positive in 81% and 70% of ADC and in 0% and 2% of SCC, respectively, whereas P63 and CK5/6 were positive in 91% and 90% of SCC and in 9% and 4% of ADC, respectively (P < .001). CD141 stained significantly higher in SCC over ADC (positive in 2% of ADC and 46% of SCC. MOC-31, CEA, COX-2, HMWCK, p27, and Rb appeared to be not useful markers in distinction between ADC and SCC because of their low specificity. None of metastatic ADC to the lung showed positive for napsin-A and TTF-1. It was evident that combination of napsin-A, TTF-1, CK5/6, and p63 was the best immunohistochemical panel in differentiating ADC from SCC of the lung in this study. CD141 appeared to be a potential new marker for SCC with high specificity. Cyclooxygenase 2, MOC-31, CEA, HMWCK, p27, and Rb showed less specificity for differentiation ADC from SCC.

BACKGROUND

Mature circulating endothelial cells (CEC) are surrogate markers of endothelial damage. CEC measured in patients with advanced cancer are thought not only to derive from damaged normal vasculature (n-CEC), but also from damaged (t-CEC). Therefore, assays that allow the discrimination between these two putative types of CEC are thought to improve the specificity of the enumeration of CEC in cancer.

METHODS

Identification of tumour-associated endothelial markers (TEM) by comparing antigen expression on normal vs t-CEC and assess the presence of t-CEC in peripheral blood of cancer patients by incorporating TEM in our novel flow cytometry-based CEC detection assay.

RESULTS

No difference in antigen expression between normal and malignant endothelial cells (ECs) was found for CD54, CD109, CD137, CD141, CD144 and CXCR7. In contrast, overexpression for CD105, CD146, CD276 and CD309 was observed in tumour ECs compared with normal ECs. CD276 was most differentially expressed and chosen as a marker for further investigation. CD276-expressing CEC were significantly higher in 15 patients with advanced colorectal cancer (median 9 (range 1-293 cell per 4 ml); P<0.005), in 83 patients with a glioblastoma multiforme (median 10 (range 0-804); P<0.0001) and in 14 patients with advanced breast cancer (median 14 (range 0-390) P<0.05) as compared with 24 healthy individuals (median 3 (range 0-11)). Of all patients with malignancies, 58% had CD276(+) CEC counts above the ULN (8 cell per 4 ml).

CONCLUSIONS

The present study shows that CD276 can be used to discriminate ECs from malignant tissue from ECs from normal tissue. In addition, CD276(+) CEC do occur in higher frequencies in patients with advanced cancer.

Disruption of the homeostatic balance of intestinal dendritic cells (DCs) and macrophages (MQs) may contribute to inflammatory bowel disease. We characterized DC and MQ populations, including their ability to produce retinoic acid, in clinical material encompassing Crohn's ileitis, Crohn's colitis and ulcerative colitis (UC) as well as mesenteric lymph nodes (MLNs) draining these sites. Increased CD14(+)DR(int) MQs characterized inflamed intestinal mucosa while total CD141(+) or CD1c(+) DCs numbers were unchanged. However, CD103(+) DCs, including CD141(+)CD103(+) and CD1c(+)CD103(+) DCs, were reduced in inflamed intestine. In MLNs, two CD14(-) DC populations were identified: CD11c(int)HLADR(hi) and CD11c(hi)HLADR(int) cells. A marked increase of CD11c(hi)HLADR(int) DC, particularly DR(int)CD1c(+) DCs, characterized MLNs draining inflamed intestine. The fraction of DC and MQ populations expressing aldehyde dehydrogenase (ALDH) activity, reflecting retinoic acid synthesis, in UC colon, both in active disease and remission, were reduced compared to controls and inflamed Crohn's colon. In contrast, no difference in the frequency of ALDH(+) cells among blood precursors was detected between UC patients and non-inflamed controls. This suggests that ALDH activity in myeloid cells in the colon of UC patients, regardless of whether the disease is active or in remission, is influenced by the intestinal environment.

Although fish constitute the most ancient animal group in which an acquired immune system is present, the presence of dendritic cells (DCs) in teleosts has been addressed only briefly, and the identification of a specific DC subset in teleosts remained elusive because of the lack of specific Abs. In mice, DCs expressing CD8α(+) in lymphoid tissues have the capacity to cross-present extracellular Ags to T cells through MHC I, similarly to tissue-derived CD103(+) DCs and the human CD141(+) DC population. In the current study, we identified a large and highly complex subpopulation of leukocytes coexpressing MHC class II and CD8α. This CD8α(+) MHC II(+) DC-like subpopulation constituted ∼1.2% of the total leukocyte population in the skin, showing phenotypical and functional characteristics of semimature DCs that seem to locally regulate mucosal immunity and tolerance in a species lacking lymph nodes. Furthermore, we identified trout homologs for CD141 and CD103 and demonstrated that, in trout, this skin CD8(+) DC-like subpopulation expresses both markers. To our knowledge, these results provide the first evidence of a specific DC-like subtype in nonimmune tissue in teleosts and support the hypothesis of a common origin for all mammalian cross-presenting DCs.

Tumors employ multiple mechanisms to evade immune surveillance. One mechanism is tumor-induced myelopoiesis, whereby the expansion of immunosuppressive myeloid cells can impair tumor immunity. As myeloid cells and conventional dendritic cells (cDCs) are derived from the same progenitors, we postulated that myelopoiesis might impact cDC development. The cDC subset, cDC1, which includes human CD141+ DCs and mouse CD103+ DCs, supports anti-tumor immunity by stimulating CD8+ T-cell responses. Here, to understand how cDC1 development changes during tumor progression, we investigated cDC bone marrow progenitors. We found localized breast and pancreatic cancers induce systemic decreases in cDC1s and their progenitors. Mechanistically, tumor-produced granulocyte-stimulating factor downregulates interferon regulatory factor-8 in cDC progenitors, and thus results in reduced cDC1 development. Tumor-induced reductions in cDC1 development impair anti-tumor CD8+ T-cell responses and correlate with poor patient outcomes. These data suggest immune surveillance can be impaired by tumor-induced alterations in cDC development.

BACKGROUND

Dendritic cells (DCs) are important in allergic diseases such as asthma, although little is known regarding the mechanisms by which DCs induce T(H)2-polarized responses in atopic individuals. It has been suggested that intrinsic properties of allergens can directly stimulate T(H)2 polarizing functions of DCs, but little is known of the underlying mechanisms.

OBJECTIVE

To identify novel genes expressed by house dust mite (HDM) allergen-exposed DCs.

METHODS

We screened for allergen-induced gene expression by microarray, and validated differentially expressed genes at the mRNA and protein levels.

RESULTS

Thrombomodulin (CD141, blood dendritic cell antigen 3) expression by microarray was higher on HDM-stimulated DCs from atopic (relative to nonatopic) individuals. These findings were confirmed at both the mRNA and protein levels in an independent group. Purified thrombomodulin(+) DCs induced a strongly T(H)2-polarized cytokine response by allergen-specific T cells compared with DCs lacking thrombomodulin. In vivo, thrombomodulin(+) circulating DCs were significantly more frequent in subjects with HDM allergy and asthma, compared with control subjects. Furthermore, thrombomodulin expression in blood leukocytes was higher in children with acute asthma than at convalescence 6 weeks later.

CONCLUSIONS

Thrombomodulin expression on DCs may be involved in the pathogenesis of atopy and asthma.

Immune-enhancing adjuvants usually targets antigen (Ag)-presenting cells to tune up cellular and humoral immunity. CD141(+) dendritic cells (DC) represent the professional Ag-presenting cells in humans. In response to microbial pattern molecules, these DCs upgrade the maturation stage sufficient to improve cross-presentation of exogenous Ag, and upregulation of MHC and costimulators, allowing CD4/CD8 T cells to proliferate and liberating cytokines/chemokines that support lymphocyte attraction and survival. These DCs also facilitate natural killer-mediated cell damage. Toll-like receptors (TLRs) and their signaling pathways in DCs play a pivotal role in DC maturation. Therefore, providing adjuvants in addition to Ag is indispensable for successful vaccine immunotherapy for cancer, which has been approved in comparison with antimicrobial vaccines. Mouse CD8α(+) DCs express TLR7 and TLR9 in addition to the TLR2 family (TLR1, 2, and 6) and TLR3, whereas human CD141(+) DCs exclusively express the TLR2 family and TLR3. Although human and mouse plasmacytoid DCs commonly express TLR7/9 to respond to their agonists, the results on mouse adjuvant studies using TLR7/9 agonists cannot be simply extrapolated to human adjuvant immunotherapy. In contrast, TLR2 and TLR3 are similarly expressed in both human and mouse Ag-presenting DCs. Bacillus Calmette-Guerin peptidoglycan and polyinosinic-polycytidylic acid are representative agonists for TLR2 and TLR3, respectively, although they additionally stimulate cytoplasmic sensors: their functional specificities may not be limited to the relevant TLRs. These adjuvants have been posted up to a certain achievement in immunotherapy in some cancers. We herein summarize the history and perspectives of TLR2 and TLR3 agonists in vaccine-adjuvant immunotherapy for cancer.

Chronic hepatitis C virus (HCV) infection is a serious disease that can result in numerous long-term complications leading to liver failure or death. Approximately 80% of people fail to clear their infection, largely as the result of weak, narrowly targeting or waning antiviral T-cell responses. Although professional antigen presenting cells (APCs) like dendritic cells (DCs) might serve as targets for modulation of T-cell immunity, the particular role of DCs in immunity to HCV is not known. Moreover the identity, phenotype, and functional characteristics of such populations in the liver, the site of HCV replication, have proven difficult to elucidate. Using a multicolor flow-based approach, we identified six distinct populations of professional APCs among liver interstitial leukocytes isolated from uninfected and HCV-infected patients. Although a generalized enrichment of DCs in the liver compared to blood was observed for all patients, HCV infection was characterized by a significant increase in the frequency of intrahepatic myeloid DCs (both CD1c+ and CD141+). Phenotypic analyses of liver plasmacytoid (pDC) and myeloid DCs (mDC) further revealed the HCV-induced expression of maturation molecules CD80, CD83, CD40, and programmed death ligand-1. Importantly, pDC and mDCs from HCV-infected liver were capable of secreting effector cytokines, interferon-alpha and interleukin-12, respectively, in response to Toll-like receptor stimulation in vitro.

CONCLUSIONS

Chronic HCV infection facilitates the "customized" recruitment of liver DC subsets with established functional roles in antigen presentation. These DCs are characterized by a mature, activated phenotype and are functionally responsive to antigenic stimulation in vitro. Such findings highlight an important paradox surrounding liver DC recruitment during HCV infection, where despite their activation these cells do not provide adequate protection from the virus.

Melanoma-induced suppression of dendritic cells (DC) in the sentinel lymph node (SLN) interferes with the generation of protective antitumor immunity. In an effort to strengthen immune defense against metastatic spread, we performed a three-arm phase II study comprising 28 patients with stage I-II melanoma randomized to receive intradermal injections around the primary tumor excision site of saline or low-dose CpG-B, alone or combined with GM-CSF, before excision of the SLNs. After pathologic examination, 5 patients were diagnosed with stage III melanoma based on the presence of tumor cells in the SLNs. Combined CpG/GM-CSF administration resulted in enhanced maturation of all identifiable conventional (cDC) and plasmacytoid (pDC) DC subsets and selectively induced increased frequencies of SLN-resident BDCA3/CD141(+) cDC subsets that also expressed the C-type lectin receptor CLEC9A. Correlative in vivo analyses and in vitro studies provided evidence that these subsets were derived from BDCA3(+) cDC precursors in the blood that were recruited to the SLNs in a type I IFN-dependent manner and subsequently matured under the combined influence of CpG and GM-CSF. In line with their reported functional abilities, frequencies of in vivo CpG/GM-CSF-induced BDCA3/CD141(+) DCs correlated with increased ex vivo cross-presenting capacity of SLN suspensions. Combined local CpG/GM-CSF delivery thus supports protective antimelanoma immunity through concerted activation of pDC and cDC subsets and recruitment of BDCA3(+) cDC subsets with T cell-stimulatory and cross-priming abilities.