Distinct Phenotype,Longitudinal Changes of Numbers and Cell-Associated Virus in Blood Dendritic Cells in SIV-Infected CD8-Lymphocyte Depleted Macaques

Loss of circulating CD123+ plasmacytoid dendritic cells (pDCs) during HIV infection is well established. However, changes of myeloid DCs (mDCs) are ambiguous since they are studied as a homogeneous CD11c+ population despite phenotypic and functional heterogeneity. Heterogeneity of CD11c+ mDCs in primates is poorly described in HIV and SIV infection. Using multiparametric flow cytometry, we monitored longitudinally cell number and cell-associated virus of CD123+ pDCs and non-overlapping subsets of CD1c+ and CD16+ mDCs in SIV-infected CD8-depleted rhesus macaques. The numbers of all three DC subsets were significantly decreased by 8 days post-infection. Whereas CD123+ pDCs were persistently depleted, numbers of CD1c+ and CD16+ mDCs rebounded. Numbers of CD1c+ mDCs significantly increased by 3 weeks post-infection while numbers of CD16+ mDCs remained closer to pre-infection levels. We found similar changes in the numbers of all three DC subsets in CD8 depleted animals as we found in animals that were SIV infected animals that were not CD8 lymphocyte depleted. CD16+ mDCs and CD123+ pDCs but not CD1c+ mDCs were significantly decreased terminally with AIDS. All DC subsets harbored SIV RNA as early as 8 days and then throughout infection. However, SIV DNA was only detected in CD123+ pDCs and only at 40 days post-infection consistent with SIV RNA, at least in mDCs, being surface-bound. Altogether our data demonstrate that SIV infection differently affects CD1c+ and CD16+ mDCs where CD16+ but not CD1c+ mDCs are depleted and might be differentially regulated in terminal AIDS. Finally, our data underline the importance of studying CD1c+ and CD16+ mDCs as discrete populations, and not as total CD11c+ mDCs.     

Flt3-ligand and granulocyte colony-stimulating factor mobilize distinct human dendritic cell subsets in vivo

Dendritic cells (DCs) have a unique ability to stimulate naive T cells. Recent evidence suggests that distinct DC subsets direct different classes of immune responses in vitro and in vivo. In humans, the monocyte-derived CD11c+ DCs induce T cells to produce Th1 cytokines in vitro, whereas the CD11c- plasmacytoid T cell-derived DCs elicit the production of Th2 cytokines. In this paper we report that administration of either Flt3-ligand (FL) or G-CSF to healthy human volunteers dramatically increases distinct DC subsets, or DC precursors, in the blood. FL increases both the CD11c+ DC subset (48-fold) and the CD11c- IL-3R+ DC precursors (13-fold). In contrast, G-CSF only increases the CD11c- precursors (>7-fold). Freshly sorted CD11c+ but not CD11c- cells stimulate CD4+ T cells in an allogeneic MLR, whereas only the CD11c- cells can be induced to secrete high levels of IFN-alpha, in response to influenza virus. CD11c+ and CD11c- cells can mature in vitro with GM-CSF + TNF-alpha or with IL-3 + CD40 ligand, respectively. These two subsets up-regulate MHC class II costimulatory molecules as well as the DC maturation marker DC-lysosome-associated membrane protein, and they stimulate naive, allogeneic CD4+ T cells efficiently. These two DC subsets elicit distinct cytokine profiles in CD4+ T cells, with the CD11c- subset inducing higher levels of the Th2 cytokine IL-10. The differential mobilization of distinct DC subsets or DC precursors by in vivo administration of FL and G-CSF offers a novel strategy to manipulate immune responses in humans.     

Characterization of myeloid and plasmacytoid dendritic cells in human lung

Dendritic cells (DCs) are bone marrow-derived mononuclear cells that play a central role in the initiation of immune responses. Because human lung DCs have been incompletely characterized, we enumerated and phenotyped mononuclear cell populations from excess lung tissue obtained at surgery. Myeloid DCs (MDCs) were identified as CD1c(+)CD11c(+)CD14(-)HLA-DR(+) cells and comprised approximately 2% of low autofluorescent (LAF) mononuclear cells. Plasmacytoid DCs (PDCs) were characterized as CD123(+)CD11c(-)CD14(-)HLA-DR(+) cells and comprised approximately 1.0% of the LAF mononuclear cells. Cells enriched in MDCs expressed CD86, moderate CD80, and little CD40, but cells enriched in PDCs had little to no expression of these three costimulatory molecules. CD11c(+)CD14(-) lineage-negative (MDC-enriched) LAF cells were isolated and shown to be much more potent in stimulating an alloreaction than CD11c(+)CD14(+) lineage-negative (monocyte-enriched) LAF cells. PDC-enriched cells were more capable of responding to a TLR-7 agonist by secreting IFN-alpha than MDC-enriched cells. MDC-enriched cells were either CD123(+) or CD123(-), but both subsets secreted cytokines and chemokines typical of MDC upon stimulation with a TLR-4 agonist and both subsets failed to secrete IFN-alpha upon stimulation with a TLR-7 agonist. By immunohistochemistry, we identified MDCs throughout different anatomical locations of the lung. However, our method did not allow the localization of PDCs with certainty. In conclusion, in the human lung MDCs were twice as numerous and expressed higher levels of costimulatory molecules than PDCs. Our data suggest that both lung DC subsets exert distinct immune modulatory functions.     

In vivo adjuvant-induced mobilization and maturation of gut dendritic cells after oral administration of cholera toxin

Although dendritic cells (DCs) regulate immune responses, they exhibit functional heterogeneity depending on their anatomical location. We examined the functional properties of intestinal DCs after oral administration of cholera toxin (CT), the most potent mucosal adjuvant. Two CD11c+ DC subsets were identified both in Peyer's patches and mesenteric lymph nodes (MLN) based on the expression of CD8alpha (CD8+ and CD8- DCs, respectively). A third subset of CD11c+CD8int was found exclusively in MLN. Feeding mice with CT induced a rapid and transient mobilization of a new CD11c+CD8- DC subset near the intestinal epithelium. This recruitment was associated with an increased production of the chemokine CCL20 in the small intestine and was followed by a massive accumulation of CD8int DCs in MLN. MLN DCs from CT-treated mice were more potent activators of naive T cells than DCs from control mice and induced a Th2 response. This increase in immunostimulating properties was accounted for by CD8int and CD8- DCs, whereas CD8+ DCs remained insensitive to CT treatment. Consistently, the CD8int and CD8- subsets expressed higher levels of costimulatory molecules than CD8+ and corresponding control DCs. Adoptive transfer experiments showed that these two DC subsets, unlike CD8+ DCs, were able to present Ags orally coadministered with CT in an immunostimulating manner. The ability of CT to mobilize immature DCs in the intestinal epithelium and to promote their emigration and differentiation in draining lymph nodes may explain the exceptional adjuvant properties of this toxin on mucosal immune responses.     

Differential regulation of human blood dendritic cell subsets by IFNs

Based on the relative expression of CD11c and CD1a, we previously identified subsets of dendritic cells (DCs) or DC precursors in human peripheral blood. A CD1a(+)/CD11c(+) population (CD11c(+) DCs), also called myeloid DCs, is an immediate precursor of Langerhans cells, whereas a CD1a(-)/CD11c(-) population (CD11c(-) DCs), sometimes called lymphoid DCs but better known as plasmacytoid DCs, is composed of type I IFN (IFN-alpha beta)-producing cells. Here, we investigate the effects of IFN-alpha beta and IFN-gamma as well as other cytokines on CD11c(+) and CD11c(-) DC subsets, directly isolated from the peripheral blood, instead of in vitro-generated DCs. IFN-gamma and IFN-alpha, rather than GM-CSF, were the most potent cytokines for enhancing the maturation of CD11c(+) DCs. Incubation of CD11c(+) DCs with IFN-gamma also resulted in increased IL-12 production, and this IL-12 allowed DCs to increase Th1 responses by alloreactive T cells. In contrast, IFN-alpha did not induce IL-12 but, rather, augmented IL-10 production. IFN-alpha-primed matured CD11c(+) DCs induced IL-10-producing regulatory T cells; however, this process was independent of the DC-derived IL-10. On the other hand, IFN-alpha by itself neither matured CD11c(-) DCs nor altered the polarization of responding T cells, although this cytokine was a potent survival factor for CD11c(-) DCs. Unlike IFN-alpha, IL-3 was a potent survival factor and induced the maturation of CD11c(-) DCs. The IL-3-primed CD11c(-) DCs activated T cells to produce IL-10, IFN-gamma, and IL-4. Thus, CD11c(+) and CD11c(-) DC subsets play distinct roles in the cytokine network, especially their responses to IFNs.     

CpG-C immunostimulatory oligodeoxyribonucleotide activation of plasmacytoid dendritic cells in rhesus macaques to augment the activation of IFN-gamma-secreting simian immunodeficiency virus-specific T cells

There are two principle subsets of dendritic cells (DCs); CD11c(+)CD123(-) myeloid DCs (MDCs) and CD11c(-)CD123(+) plasmacytoid DCs (PDCs). DC activation via TNF-TNFRs (e.g., CD40L) and TLRs (e.g., immunostimulatory oligodeoxyribonucleotides (ISS-ODNs)) is crucial for maximal stimulation of innate and adaptive immunity. Macaque DC biology is being studied to improve HIV vaccines using the SIV macaque model. Using lineage (Lin) markers to exclude non-DCs, Lin(-)HLA-DR(+)CD11c(+)CD123(-) MDCs and Lin(-)HLA-DR(+)CD11c(-)CD123(+) PDCs were identified in the blood of uninfected macaques and healthy macaques infected with SIV or simian-human immunodeficiency virus. Overnight culture of DC-enriched Lin-depleted cells increased CD80 and CD86 expression. IL-12 production and CD80/CD86 expression by MDC/PDC mixtures was further enhanced by CD40L and ISS-ODN treatment. A CpG-B ISS-ODN increased CD80/CD86 expression by PDCs, but resulted in little IFN-alpha secretion unless IL-3 was added. In contrast, a CpG-C ISS-ODN and aldrithiol-2-inactivated (AT-2) SIV induced considerable PDC activation and IFN-alpha release without needing exogenous IL-3. The CpG-C ISS-ODN also stimulated IL-12 release (unlike AT-2 SIV) and augmented DC immunostimulatory activity, increasing SIV-specific T cell IFN-gamma production induced by AT-2 SIV-presenting MDC/PDC-enriched mixtures. These data highlight the functional capacities of MDCs and PDCs in naive as well as healthy, infected macaques, revealing a promising CpG-C ISS-ODN-driven DC activation strategy that boosts immune function to augment preventative and therapeutic vaccine efficacy.     

Human immunodeficiency virus type 1 activates plasmacytoid dendritic cells and concomitantly induces the bystander maturation of myeloid dendritic cells

In this study, we analyzed the phenotypic and physiological consequences of the interaction of plasmacytoid dendritic cells (pDCs) with human immunodeficiency virus type 1 (HIV-1). pDCs are one cellular target of HIV-1 and respond to the virus by producing alpha/beta interferon (IFN-alpha/beta) and chemokines. The outcome of this interaction, notably on the function of bystander myeloid DC (CD11c+ DCs), remains unclear. We therefore evaluated the effects of HIV-1 exposure on these two DC subsets under various conditions. Blood-purified pDCs and CD11c+ DCs were exposed in vitro to HIV-1, after which maturation markers, cytokine production, migratory capacity, and CD4 T-cell stimulatory capacity were analyzed. pDCs exposed to different strains of infectious or even chemically inactivated, nonreplicating HIV-1 strongly upregulated the expression of maturation markers, such as CD83 and functional CCR7, analogous to exposure to R-848, a synthetic agonist of toll-like receptor-7 and -8. In addition, HIV-1-activated pDCs produced cytokines (IFN-alpha and tumor necrosis factor alpha), migrated in response to CCL19 and, in coculture, matured CD11c+ DCs, which are not directly activated by HIV. pDCs also acquired the ability to stimulate na?ve CD4+ T cells, albeit less efficiently than CD11c+ DCs. This HIV-1-induced maturation of both DC subsets may explain their disappearance from the blood of patients with high viral loads and may have important consequences on HIV-1 cellular transmission and HIV-1-specific T-cell responses.     

Functional specializations of intestinal dendritic cell and macrophage subsets that control Th17 and regulatory T cell responses are dependent on the T cell/APC ratio, source of mouse strain, and regional localization

Although several subsets of intestinal APCs have been described, there has been no systematic evaluation of their phenotypes, functions, and regional localization to date. In this article, we used 10-color flow cytometry to define the major APC subsets in the small and large intestine lamina propria. Lamina propria APCs could be subdivided into CD11c(+)CD11b(-), CD11c(+)CD11b(+), and CD11c(dull)CD11b(+) subsets. CD11c(+)CD11b(-) cells were largely CD103(+)F4/80(-) dendritic cells (DCs), whereas the CD11c(+)CD11b(+) subset comprised CD11c(+)CD11b(+)CD103(+)F4/80(-) DCs and CD11c(+)CD11b(+)CD103(-)F4/80(+) macrophage-like cells. The majority of CD11c(dull)CD11b(+) cells were CD103(-)F4/80(+) macrophages. Although macrophages were more efficient at inducing Foxp3(+) regulatory T (T(reg)) cells than DCs, at higher T cell/APC ratios, all of the DC subsets efficiently induced Foxp3(+) T(reg) cells. In contrast, only CD11c(+)CD11b(+)CD103(+) DCs efficiently induced Th17 cells. Consistent with this, the regional distribution of CD11c(+)CD11b(+)CD103(+) DCs correlated with that of Th17 cells, with duodenum > jejunum > ileum > colon. Conversely, CD11c(+)CD11b(-)CD103(+) DCs, macrophages, and Foxp3(+) T(reg) cells were most abundant in the colon and scarce in the duodenum. Importantly, however, the ability of DC and macrophage subsets to induce Foxp3(+) T(reg) cells versus Th17 cells was strikingly dependent on the source of the mouse strain. Thus, DCs from C57BL/6 mice from Charles River Laboratories (that have segmented filamentous bacteria, which induce robust levels of Th17 cells in situ) were more efficient at inducing Th17 cells and less efficient at inducing Foxp3(+) T(reg) cells than DCs from B6 mice from The Jackson Laboratory. Thus, the functional specializations of APC subsets in the intestine are dependent on the T cell/APC ratio, regional localization, and source of the mouse strain.     

CD34+-derived CD11c+ + + BDCA-1+ + CD123+ + DC: expansion of a phenotypically undescribed myeloid DC1 population for use in adoptive immunotherapy

BACKGROUND: DC are commonly defined as HLA-DR+/Lin- cells that can be CD11c+ + + CD123+/ -, termed DC1/myeloid DC that induce a Th1 response, or CD11c- CD123+ + +, termed DC2/lymphoid DC that induce a Th2 response. However, significant heterogeneity within DC preparations is apparent and supports the existence of several distinct DC subpopulations. This study aimed to expand and characterize CD34+ DC for use in immunotherapy. METHODS: CD34+ cells were seeded at 1 x 10(5)/mL and expanded for 14 days in RPMI + 10% autologous plasma supplemented with GM-CSF, IL-4, Flt-3L and SCF. Maturation was induced with TNF-alpha and PGE2 for 2 days. DC were analyzed morphologically, phenotypically with a panel of MAb to lineage and DC markers, and functionally in MLR, T-cell assays and T-cell cytokine secretion by ELISA. RESULTS: Significant cellular expansion was observed: 60+/-5 x 10(6) DC from 1 x 10(6) CD34+ cells (n=28). Phenotypically DC were characterized as HLA-DR+ +, CD11c+ + +, CD80+ +, CD83+, CD86+ +, CD123+ +, CD15+ +, CD33+ +, BDCA-1+ +, CD4+ and Lin-. DC displayed potent allostimulatory capacity and efficient presentation of KLH and tetanus toxin. DC-primed T cells secreted IFN-gamma (Th1); however, no detectable IL-4 (Th2) was noted. DISCUSSION: We present features of CD34+ DC that have not been previously described. The CD34+ DC generated represent a population of myeloid DC functioning as DC1 but phenotypically expressing markers characteristic of both DC1 and DC2. This novel DC population is capable of inducing naive T-cell responses and can be expanded to clinically useful numbers. CD34+-derived DC represent attractive candidates for use in adoptive T-cell immunotherapy.     

Enterovirus-Infected β-Cells Induce Distinct Response Patterns in BDCA1+ and BDCA3+ Human Dendritic Cells

Enteroviruses often cause mild disease, yet are also linked to development of autoimmune diabetes. Dendritic cells (DCs) shape both innate and adaptive immune responses, including anti-viral responses. How different human DC subsets shape anti-viral responses, whether they have complementary or overlapping functions and how this relates to autoimmune responses is largely unknown. We used enterovirus-infected β-cells and freshly isolated human myeloid DC (mDC) subsets as a model for autoimmune type 1 diabetes. Our data show that both the BDCA1⁺ and BDCA3⁺ mDC subsets engulf mock- as well as virus-infected β-cells, albeit BDCA1⁺ mDCs are more efficient. Uptake of enterovirus-infected, but not mock-infected cells, activated both DC subsets as indicated by the induction of co-stimulatory molecules and secretion of type I and type III interferons. Both subsets produced similar amounts of interferon-α, yet the BDCA3⁺ DC were superior in IFN-λ production. The BDCA1⁺ mDCs more strongly upregulated PD-L1, and were superior in IL-12 and IL-10 production as compared to the BDCA3⁺ DC. Despite lack of IL-12 production by the BDCA3+ DC, both BDCA1⁺ and BDCA3⁺ DCs activated T cells in allogeneic mixed lymphocyte reaction towards a Th1-type reactivity while suppressing Th2-associated cytokines.     

Relationship between peripheral blood dendritic cells and cytokines involved in the pathogenesis of systemic lupus erythematosus

Recent studies indicate that dendritic cells (DC) and several cytokines are implicated in the induction of autoimmune diseases. In this study we investigated the relationship between the total number of DC (tDC), and their plasmacytoid (pDC) and myeloid (mDC) subpopulations, with serum concentrations of interferons (IFN-alpha and IFN-gamma) and selected cytokines (TNF-alpha, IL-4, IL-6), in patients with systemic lupus erythematosus (SLE) and healthy persons. Subpopulations of DC were determined by the following antigen expression profiles: BDCA-1+\CD11c+\HLA-DR+ (for mDC) and BDCA-2 +\CD123+\HLA-DR+ (for pDC), using flow cytometry. Serum levels of interferons and cytokines were assessed by an enzyme-linked immunosorbent assay (ELISA). The study was performed in 36 SLE patients and 19 healthy volunteers. The mean number of tDC was lower in SLE patients (13.9 +/- 6.4\microL) than in healthy persons (24.1 +/- 12.6\microL) (P < 0.001). The number of pDC was also significantly lower in SLE (6.6 +/- 3.6\microL) than in the control group (12.0 +/- 8.3\microL) (P < 0.02). Moreover, the mean pDC count was lower in active than in inactive disease (5.5 +/- 3.6\microL vs 7.6 +/- 3.4\microL; P < 0.04). The mean serum levels of IFN-alpha and IFN-gamma were significantly higher in SLE patients (63.8 pg\mL and 6.6 pg\mL, respectively) than in the control group (2.7 pg\mL and 0.5 pg\mL, respectively) (P < 0.008 and P < 0.001, respectively). Serum levels of TNF-alpha and IL-6 were also higher in SLE patients (mean 7.3 pg\mL and 18.4 pg\mL, respectively) than in healthy controls (4.2 pg\mL and 0.5 pg\mL, respectively) (P < 0.02 and P < 0.001, respectively). The mean serum IL-4 concentrations were similar in SLE and healthy persons (0.2 pg\mL and 0.31 pg\mL, respectively; P -/+ 0.119). A negative correlation was found between pDC number and the serum level of IFN-alpha (rho -/+ -- 0.386, P -/+ 0.02) and between mDC and IFN-gamma (rho -/+ -- 0.377, P -/+ 0.024). In conclusion, the correlation between peripheral blood DC subsets and serum levels of IFN-alpha and IFN-gamma suggests a possible relationship between these cytokines in the pathogenesis of SLE.     

The distribution of peripheral blood dendritic cells assayed by a new panel of anti-BDCA monoclonal antibodies in healthy representatives of the polish population

A growing number of studies are being performed on the role of dendritic cells (DCs) in the etiopathogenesis of various conditions. Therefore, it is extremely important to establish the best comparable methods for the determination of the absolute count of blood dendritic cells (BDCs) or their subsets, and the reference normal values for comparisons. The aim of our study was to assess a normal profile of BDCs in the non-cultured human blood of healthy Polish volunteers. BDCs were detected among peripheral blood mononuclear cells (PBMC) from 99 healthy people, aged 18-56. Based on the panel of novel anti-BDCA1, BDCA2 and BDCA3 monoclonal antibodies (MoAbs), three main subpopulations of BDCs were distinguished: two myeloid types of BDCs, MDC1(BDCA-1+/ CD11c+ /HLA-DR+) or MDC2 (BDCA-3+/CD32-/CD64-/HLA-DR+), and a plasmacytoid subtype, PDC (BDCA-2+/CD123+/HLA-DR+). The number and percentage of BDCs were correlated with the age, gender, photosensitivity (phototype, minimal erythemal dose -- MED) and morphological parameters of the healthy volunteers. BDCs represented 0.83% of the PBMC and the median total BDC number was 44.0 cell/microl. The total BDC number correlated with the WBC count (rho=0.40, p=0.001) as well as with the lymphocyte and monocyte counts (rho=0.20, p=0.045 and rho=0.26, p=0.009, respectively). The median percentage of the MDC1 count (0.20%) was twice as high as the MDC2 count (0.10%). The median PDC count was 28.2 cell/microl, and these cells represented 0.50% of the PBMC. There was a positive correlation between PDC and skin photosensitivity (rho=0.28, p=0.005). An inverse correlation between the PDC count and the age of the examined volunteers was also found (rho=-0.22, p=0.029). Our study provides the first referential data on normal rates and counts of BDCs and their subpopulations, assessed by the new panel of anti-BDCA MoAbs, in healthy Polish subjects. The method used in the study allowed the determination of BDCs and their subset numbers in a relatively small blood volume.     

Involvement of intestinal epithelial cells in dendritic cell recruitment during C. parvum infection

Dendritic cells (DCs) play a key role in activating and orientating immune responses. Little is currently known about DC recruitment during Cryptosporidium parvum infection. In the intestine, epithelial cells act as sensors, providing the first signals in response to infection by enteric pathogens. We analyzed the contribution of these cells to the recruitment of DCs during cryptosporidiosis. We found that intestinal epithelial cells produced a broad range of DC-attracting chemokines in vitro in response to C. parvum infection. The supernatant of the infected cells induced the migration of both bone marrow-derived DCs (BMDC) and the SRDC lymphoid dendritic cell line. Chemokine neutralization abolished DC migration in these assays. We next analyzed chemokine mRNA expression in the mucosa of C. parvum-infected neonatal mice and recruitment of the various subsets of DCs. Myeloid (CD11c+ CD11b+) and double-negative DCs (CD11c+ CD11b- CD8alpha-) were the main subsets recruited in the ileum during C. parvum infection, via a mechanism involving IFNgamma. DCs were also recruited and activated in the draining lymph nodes during C. parvum infection, as shown by the upregulation of expression of MHC II and of the costimulation molecules CD40 and CD86.     

Compartmental imbalance and aberrant immune function of blood CD123+ (plasmacytoid) and CD11c+ (myeloid) dendritic cells in atopic dermatitis

Atopic dermatitis (AD) is a pruritic, chronically relapsing skin disease in which Th2 cells play a crucial role in cutaneous and extracutaneous immune reactions. In humans, CD11c+CD123- myeloid dendritic cells (mDC) and CD11c-CD123+ plasmacytoid DC (pDC) orchestrate the decision-making process in innate and acquired immunity. Since the number and function of these blood dendritic cell (DC) subsets reportedly reflect the host immune status, we studied the involvement of the DC subsets in the pathogenesis of AD. Patients with AD had an increased DC number and a low mDC:pDC ratio with pDC outnumbering mDC in the peripheral blood compared with normal subjects and psoriasis patients (a Th1 disease model group). The mDC:pDC ratio was correlated with the total serum IgE level, the ratio of IFN-gamma-producing blood cells:IL-4-producing blood cells, and the disease severity. In vitro allogeneic stimulation of naive CD4+ cells with atopic DC showed that the ability of pDC for Th1 induction was superior or comparable to that of mDC. In skin lesions, pDC infiltration was in close association with blood vessels expressing peripheral neural addressins. Therefore, compartmental imbalance and aberrant immune function of the blood DC subsets may deviate the Th1/Th2 differentiation and thus induce protracted allergic responses in AD.     

Identification of ITGA4/ITGB7 and ITGAE/ITGB7 expressing subsets of decidual dendritic-like cells within distinct microdomains of the pregnant mouse uterus

Several leukocyte populations have been described within the pregnant mouse uterus, some of which express the integrin beta 7 (ITGB7). Here we demonstrate that the majority of the ITGB7(+) decidual leukocytes belong to the dendritic cell (DC) lineage. By multiparameter flow cytometric analysis we demonstrated the existence of three distinct DC subsets, characterized by differential expression of ITGA4/ITGB7 (formerly alpha4beta7-integrin) and ITGAE/ITGB7 (formerly alphaEbeta7-integrin). Importantly, the predominant DC subsets reside in distinct microdomains of the Day 9 pregnant mouse uterus. ITGAX(+) ITGAM(med) ITGA4/ITGB7(+) ITGAE(-) (formerly CD11c(+) CD11b(med) alpha4beta7(+) alphaE(-)) cells represent the majority of DCs in the vascular zone (VZ), whereas ITGAX(+) ITGAM(-) ITGAE/ITGB7(+) (formerly CD11c(+) CD11b(-) alphaEbeta7(+)) DCs are mainly located in the lower central decidua basalis (cDB) and the underlying myometrium. A population of ITGAX(+) ITGAM(low) DCs lacking ITGB7 are restricted to the cDB. Confocal microscopy studies show direct contact of VZ DCs with uterine natural killer (uNK) cells, suggesting a functional relationship between both cell populations. Collectively, our data identify three phenotypically distinct DC subsets residing in distinct microdomains of the uterus. The differential expression of ITGA4/ITGB7 and ITGAE/ITGB7 suggests distinct functional roles of the different DC subsets during early pregnancy.     

Cutting edge: mTORC1 in intestinal CD11c+ CD11b+ dendritic cells regulates intestinal homeostasis by promoting IL-10 production

The mammalian target of rapamycin (mTOR) controls cell growth and survival through two distinct complexes called mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Although several reports have suggested the involvement of mTORC1 in development and function of dendritic cells (DCs), its physiological roles remain obscure. We therefore established mTORC1 signal-deficient mice lacking Raptor, an essential component of mTORC1 signal, specifically in DC lineage (referred to here as Raptor(DC-/-)). Raptor(DC-/-) mice exhibited cell expansion in specific subsets of DCs such as splenic CD8(+) DCs and intestinal CD11c(+)CD11b(+) DCs. We also found that impaired mTORC1 signal resulted in the suppression of IL-10 production along with enhanced CD86 expression in intestinal CD11c(+)CD11b(+) DCs and that Raptor(DC-/-) mice were highly susceptible to dextran sodium sulfate-induced colitis. Our results uncover mTORC1-mediated anti-inflammatory programs in intestinal CD11c(+)CD11b(+) DCs to limit the intestinal inflammation.