Research in vitro facilitates discovery, screening, and pilot experiments, often preceding research in vivo. Several technical difficulties render Dendritic Cell (DC) research particularly challenging, including the low frequency of DC in vivo, thorough isolation requirements, and the vulnerability of DC ex vivo. Critically, there is not as yet a widely accepted human or murine DC line and in vitro systems of DC research are limited. In this study, we report the generation of new murine DC lines, named MutuDC, originating from cultures of splenic CD8α conventional DC (cDC) tumors. By direct comparison to normal WT splenic cDC subsets, we describe the phenotypic and functional features of the MutuDC lines and show that they have retained all the major features of their natural counterpart in vivo, the splenic CD8α cDC. These features include expression of surface markers Clec9A, DEC205, and CD24, positive response to TLR3 and TLR9 but not TLR7 stimuli, secretion of cytokines, and chemokines upon activation, as well as cross-presentation capacity. In addition to the close resemblance to normal splenic CD8α cDC, a major advantage is the ease of derivation and maintenance of the MutuDC lines, using standard culture medium and conditions, importantly without adding supplementary growth factors or maturation-inducing stimuli to the medium. Furthermore, genetically modified MutuDC lines have been successfully obtained either by lentiviral transduction or by culture of DC tumors originating from genetically modified mice. In view of the current lack of stable and functional DC lines, these novel murine DC lines have the potential to serve as an important auxiliary tool for DC research.

Immune responses against intestinal microbiota contribute to the pathogenesis of inflammatory bowel diseases (IBD) and involve CD4+ T cells, which are activated by major histocompatibility complex class II (MHCII) molecules on antigen-presenting cells (APCs). However, it is largely unexplored how inflammation-induced MHCII expression by intestinal epithelial cells (IEC) affects CD4+ T cell-mediated immunity or tolerance induction in vivo. Here, we investigated how epithelial MHCII expression is induced and how a deficiency in inducible epithelial MHCII expression alters susceptibility to colitis and the outcome of colon-specific immune responses. Colitis was induced in mice that lacked inducible expression of MHCII molecules on all nonhematopoietic cells, or specifically on IECs, by continuous infection with Helicobacter hepaticus and administration of interleukin (IL)-10 receptor-blocking antibodies (anti-IL10R mAb). To assess the role of interferon (IFN)-γ in inducing epithelial MHCII expression, the T cell adoptive transfer model of colitis was used. Abrogation of MHCII expression by nonhematopoietic cells or IECs induces colitis associated with increased colonic frequencies of innate immune cells and expression of proinflammatory cytokines. CD4+ T-helper type (Th)1 cells - but not group 3 innate lymphoid cells (ILCs) or Th17 cells - are elevated, resulting in an unfavourably altered ratio between CD4+ T cells and forkhead box P3 (FoxP3)+ regulatory T (Treg) cells. IFN-γ produced mainly by CD4+ T cells is required to upregulate MHCII expression by IECs. These results suggest that, in addition to its proinflammatory roles, IFN-γ exerts a critical anti-inflammatory function in the intestine which protects against colitis by inducing MHCII expression on IECs. This may explain the failure of anti-IFN-γ treatment to induce remission in IBD patients, despite the association of elevated IFN-γ and IBD.

IntroductionDendritic cells (DCs) are the antigen-presenting cells (APCs) capable of inducing adaptive immune responses and tolerance. 1 DCs act as sentinels in peripheral tissues and as APCs in secondary lymphoid organs, filtering their environment and detecting environmental changes that modulate the balance between tolerance and immune response. Following infection and inflammation, DCs induce costimulatory molecules, secrete cytokines, and can change their migration properties. 2,3 Several DC subtypes with unique and overlapping functions have been described. Plasmacytoid DCs (pDCs) are the main interferon (IFN) type I-producing cells, whereas several subtypes of conventional DCs (cDCs) are widely distributed. 4,5 In skin, 2 DC populations, namely Langerhans cells (LCs) and dermal DCs, localize to the epidermis and dermis, respectively. Upon pathogen encounter, they migrate to the draining LN. 6 In skin and spleen, DCs are derived either from blood or from immediate local precursors. [7][8][9][10][11][12][13] DCs are dividing cells rather than terminally differentiated cells. [12][13][14][15] The importance of DC cycling on their homeostasis is currently debated, and DC proliferation has been recently proposed to extend the duration of antigen presentation. 15 The human histiocytic diseases are characterized by abnormal accumulation or proliferation of macrophages or DCs. 16 They are divided into LC or non-LC histiocytosis. In the former category, LC histiocytosis (LCH) is best described. LCH can range from a spontaneously regressing single organ disease to a life-threatening or disabling relapsing multisystem disease. 16 In the latter category, a genetic deficiency in cytotoxic activity, familial hemophagocytic lymphohistiocytosis (FHL), is the principal type implicating macrophages and lymphocytes. In contrast to LCH and FHL, lesions with proliferative DCs with or without cytologic atypia are less well classified and their prevalence remains controversial. 16 Unfortunately, a confusing terminology describing these cases of proliferating DCs persists in the literature as malignant histiocytosis, histiocytic sarcoma, and DC sarcoma.The diagnosis of histiocytic diseases relies on the morphologic, ultrastructural, and immunohistochemical histiocyte properties. The macrophage, DC, or LC lineage markers allow LC to be distinguished from non-LC histiocytosis. For example, diagnostic criteria for LCH include expression of Langerin or detection of Birbeck granules that are pathognomonic, as well as CD1a and S100, which are less specific. According to the International Lymphoma Study Group, histiocytic sarcoma, LC tumor, and LC sarcoma (LCS) are the terms used to separate cases based on the degree of cytologic atypia and on lineage markers. 17 For example, diagnosis of LCS requires the same markers as LCH and the additional presence of cellular and mitotic atypia.While LCS, LC, and DC tumors are clearly neoplastic, it is vigorously debated whether LCH is a reactive or a neoplastic The online version of this article ...

Keywords: Batf-3 r CD8α + dendritic cells r Leishmania majorAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionThe immune response to Leishmania major in mice has highlighted the relevance of Th1/Th2 cell differentiation in determining the outcome of infection in vivo. C57BL/6 mice develop self-healing lesions characterized by a Th1 cell response with high levels of IFN-γ secreted by CD4 + T cells, which activates the antimicrobial Correspondence: Prof. Hans Acha-Orbea e-mail: hans.acha-orbea@unil.chproperties of macrophages [1,2]. In contrast, BALB/c mice develop nonhealing lesions associated with Th2-and Th17-cell immune responses with high levels of IL-4, IL-5, . The adaptive immune response is largely initiated by dermal and draining lymph node (dLN)-resident DC subsets [7]. DCs are antigen-presenting cells expressing a large number of costimulatory molecules that efficiently prime T cells. Several DC subsets have been described based on their origin, phenotypic characteristics, and location [8]. However, the role of the different subsets in L. major is debated due to the varying routes of administration, strain of parasite, and dosage of parasite inoculated that C 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2014. 44: 1422-1432 Immunity to infection 1423 have been used in the studies [4]. Inflammatory monocyte DCs (iDCs) develop at the site of infection, and upon infection, migrate to the dLNs where they present Leishmania antigens to T cells [9][10][11] Results Batf3−/− mice on a C57BL/6 background display increased susceptibility to L. major Batf3−/− mice were infected with 3 × 10 6 L. major promastigotes in the hind footpad and lesion size was monitored over several weeks. In comparison to WT C57BL/6 mice, Batf3 −/− mice developed significantly larger lesion size after 6 weeks of infection while in C57BL/6 mice, the lesions decreased thereafter (Fig. 1A). To study whether the enhanced lesion size correlated with increased parasite burden, we determined the parasite load at 3, 6, and 10 weeks postinfection. Parasite burden was significantly higher by 3 weeks and increased at 6 weeks postinfection, when significant differences in the lesion size between Batf3 −/− and C57BL/6 mice began to appear (Fig. 1B). The peak of infection at 10 weeks corresponded to the peak of parasite load as well. L. major-infected Batf3 −/− dLNs have significantly higher numbers of cells including some DC subsetsWe next assessed the composition of the dLN in L. major-infected mice at 3, 6, and 10 weeks postinfection. Mice were sacrificed at various time points and T cells, B cells, iDCs, CD11b + , CD8α + as well as plasmacytoid DCs (pDCs) were identified using the gating strategy depicted in Fig. 2A. Infected Batf3 −/− mice had significantly higher absolute number of dLN cells at 6 and 10 weeks postinfection ( Fig. 2B), a feature also observed in L. majorsusceptible BALB/c mice (data not shown). Since differences in...

Xanthine oxidoreductase has been implicated in cancer. Nonetheless, the role played by its two convertible forms, xanthine dehydrogenase (XDH) and oxidase (XO) during tumorigenesis is not understood. Here we produce XDH-stable and XO-locked knock-in (ki) mice to address this question. After tumor transfer, XO ki mice show strongly increased tumor growth compared to wild type (WT) and XDH ki mice. Hematopoietic XO expression is responsible for this effect. After macrophage depletion, tumor growth is reduced. Adoptive transfer of XO-ki macrophages in WT mice increases tumor growth. In vitro, XO ki macrophages produce higher levels of reactive oxygen species (ROS) responsible for the increased Tregs observed in the tumors. Blocking ROS in vivo slows down tumor growth. Collectively, these results indicate that the balance of XO/XDH plays an important role in immune surveillance of tumor development. Strategies that inhibit the XO form specifically may be valuable in controlling cancer growth.