Highly biocompatible multifunctional nanocomposites consisting of monodisperse manganese oxide nanoparticles with luminescent silica shells were synthesized by a combination of w/o-microemulsion techniques and common sol-gel procedures. The nanoparticles were characterized by TEM analysis, powder XRD, SQUID magnetometry, FT-IR, UV/vis and fluorescence spectroscopy and dynamic light scattering. Due to the presence of hydrophilic poly(ethylene glycol) (PEG) chains on the SiO 2 surface, the nanocomposites are highly soluble and stable in various aqueous solutions, including physiological saline, buffer solutions and human blood serum. The average number of surface amino groups available for ligand binding on the particles was determined using a colorimetric assay with fluorescein isothiocyanate (FITC). This quantification is crucial for the drug loading capacity of the nanoparticles. SiO 2 encapsulated MnO@SiO 2 nanoparticles were less prone to Mn-leaching compared to nanoparticles coated with a conventional bi-functional dopamine-PEG ligand. The presence of a silica shell did not change the magnetic properties significantly, and therefore, the MnO@SiO 2 nanocomposite particles showed a T 1 contrast with relaxivity values comparable to those of PEGylated MnO nanoparticles. The cytotoxicity of the MnO@SiO 2 -PEG/NH 2 nanoparticles was evaluated using primary cells of the innate immune system with bone marrow-derived polymorphonuclear neutrophils (BM-PMNs) as import phagocytes in the first line of defence against microbial pathogens, and bone marrow-derived dendritic cells (BMDCs), major regulators of the adaptive immunity. MnO@SiO 2 -PEG/NH 2 nanoparticles have an acceptable toxicity profile and do not interact with BMDCs as shown by the lack of activation and uptake.

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Immunologic approaches to combat cancer aim at the induction of tumor-reactive immune responses to achieve long-term protection. In this context, we recently developed a transcutaneous immunization (TCI) method using the Toll-like receptor (TLR) 7 agonist imiquimod and a peptide epitope. Application onto intact skin induces potent cytotoxic T lymphocyte (CTL) responses and protection against transplanted tumors. The purpose of this study was to explore the effects of UV irradiation on imiquimod-based TCI. Here we show that skin exposure to low-dose UV light before TCI with imiquimod strongly boosts specific CTL responses leading to memory formation and enhanced tumor protection. Toward the mechanisms, we show that the activation of bone-marrow-derived dermal dendritic cells (DCs), but not Langerin-expressing DCs, is responsible for enhanced CTL activation. We describe an optimized TCI method that mediates enhanced CTL and antitumor responses by a DC- and TLR-dependent mechanism. These data may provide the basis for the future development of advanced vaccination protocols against tumors and persistent virus infections.

Graft-versus-host disease (GvHD) is a frequent life-threatening complication following allogeneic HSC transplantation (HSCT). IL-10 is a regulatory cytokine with important roles duringGvHD, yet its relevant sources, and mode of action, remain incompletely defined in this disease. Using IL-10-deficient donor or host mice (BALB/c or C57BL/6, respectively) in a MHC-mismatched model for acute GvHD, we found a strongly aggravated course of the disease with increased mortality when either donor or host cells could not produce this cytokine. A lack of IL-10 resulted in increased allogeneic T-cell responses and enhanced activation of host DCs in spleen and MLNs. Remarkably, IL-10 was prominently produced by host-and donor-derived CD5 int CD1d int TIM-1 int B cells in this disease, and consistent with this, allogeneic HSCT resulted in exacerbated GvHD when mice lacking IL-10 expression in B cells were used as donor or host, compared with controls. Taken together, this study demonstrates that host and donor B cell-derived IL-10 provides a unique mechanism of suppression of acute GvHD, and suggests that DCs are the targets of this B cell-mediated suppressive effect. These findings open novel therapeutic possibilities based on the use of B cells to increase the feasibility of allogeneic HSCT. Keywords: B cells r IL-10 r Graft-versus-host diseaseAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionAllogeneic HSC transplantation (HSCT) is the treatment of choice for patients with high-risk haematological malignancies, because Eur. J. Immunol. 2014. 44: 1857-1865 immune cells, and their production of inflammatory cytokines [2]. For instance, host cells can contribute to GvHD through the release of TNF-α and IL-1, which are induced upon application of the conditioning regimen (chemo-or radiotherapy), and donor T cells can secrete IL-2 as well as IFN-γ upon activation in the host. In addition, activated cytotoxic T lymphocytes can provoke direct host tissue damage through cell-mediated cytotoxicity. The existence of inflammation in GvHD suggests that cytokines with anti-inflammatory properties might be able to inhibit the development of this disease. In this regard, IL-10 is of particular interest because clinical studies have already underscored the influence of Il-10 gene polymorphisms, and of IL-10 levels prior to HSCT [3], on incidence and outcome of GvHD [4]. However, IL-10 can apparently mediate various effects in GvHD, as indicated by results from murine models in which it suppressed [5] or enhanced GvHD [6] depending on the dose [7]. It is well known that IL-10 can be stimulatory or inhibitory, depending on the cell types producing and receiving it [8]. IL-10 can be secreted by several subsets of hematopoietic and nonhematopoietic cells [9], and there is considerable debate over the nature of the relevant source of IL-10 during GvHD. Possible candidates are donor-derived Treg cells [10], bone marrow cells [11], DCs [12], and host-derived B cells [13...