Patients with chronic renal failure maintained on intermittent hemodialysis have frequent infections and a suboptimal response to vaccinations. Dendritic cells are potent antigen-presenting cells essential for the initiation and maintenance of innate and adaptive immunity. In this study we used uremic sera from hemodialysis patients to measure its impact on monocyte and monocyte-derived dendritic cell function in vitro. Monocytes from healthy and uremic subjects were isolated using immunomagnetic beads and differentiated into dendritic cells in the presence of either complete sera or sera from hemodialysis patients. Dendritic cells from normal patients cultured in uremic sera had decreased endocytosis and impaired maturation. These cells, however, had enhanced IL-12p70 production and increased allogeneic T-cell proliferation compared to cells of normal subjects cultured in normal sera. Monocyte derived dendritic cells of hemodialysis patients cultured in either normal or uremic sera were functionally impaired for endocytosis and maturation but had enhanced IL-12p70 production and allogeneic T-cell proliferation only when cultured with uremic sera. High concentrations of urea in normal sera inhibited all aspects of normal dendritic cell function in vitro. Our study suggests that hemodialysis regimes tailored to remove uremic toxins more efficiently may improve immune functions of these patients.

Epstein-Barr virus (EBV) is IntroductionEpstein-Barr virus (EBV) is a ubiquitous, potentially oncogenic human herpes virus affecting up to 95% of the adult population worldwide. Primary infection often occurs in childhood 1 as asymptomatic or mild self-limiting illness or as infectious mononucleosis in adults. 2 In immunocompromised patients with impaired cellmediated immunity, acute EBV infection is associated with the development of lymphoproliferative disease (LPD) with mortality rates between 10% and 100%. 3 In recipients of solid organ transplants, the incidence of posttransplant lymphoproliferative disease (PTLD) ranges from 1% to 15%, with the highest risk in EBV IgG-seronegative recipients receiving a graft from EBV IgG-seropositive donors. 4 Dendritic cells (DCs) are a rare, heterogenous population of antigen-presenting cells (APCs) that initiate and regulate both innate and adaptive immune responses against invading pathogens. [5][6][7] There are at least 2 circulating blood DC subsets including myeloid DC (MDCs) and plasmacytoid DC (PDCs). 8,9 Although both DC subsets are involved in the initial response against infectious agents, PDCs play a key role in antiviral immunity. PDC precursors (pre-PDCs) express distinct lymphoid markers including pre-T␣, 5, Ig1-like 14.1, and Spi-B; blood DC antigen 2 (BDCA-2) and BDCA-4 (neuropilin-1) 11 ; and toll-like receptor 7 (TLR-7) and TLR-9. 12,13 Viral stimulation of TLR-7 and TLR-9 expressed on PDCs results in production of type I interferons (IFNs), 12,13 key cytokines in antiviral response. 10,14,15 Humanized severe combined immunodeficiency (SCID) mice are a well-established model of spontaneous EBV-induced B-cell lymphoma. 16 Nonobese diabetic (NOD)-SCID mice possess additional immunologic defects (eg, decreased murine natural killer [NK] cell function) that permit greater engraftment of human cells following injection of human peripheral blood mononuclear cells (PBMCs). 17 In a previous study, we demonstrated that circulating pre-PDCs are severely reduced in the peripheral blood of renal transplant recipients resulting in impaired IFN-␣ production by PBMCs following viral stimulation. 18 We hypothesized that the reduction in circulating pre-PDCs observed in transplant recipients plays a crucial role in the risk of viral infection, and in particular EBV-related infection and the onset of LPD. In the present study, we address this hypothesis by assessing the impact of a reduction in the numbers of circulating PDCs in the development of EBVrelated infection and LPD using a humanized NOD-SCID mouse model as a surrogate model of human EBV infection. We demonstrate that reduction in PDCs enhances the development of EBV-related infection and LPD, whereas the supplementation of extra PDCs delays or even prevents the development of EBVrelated LPD in humanized NOD-SCID mice. We now show for the first time that PDCs are involved in anti-EBV immunity by the secretion of IFN-␣ and activation of T cells mediated by TLR-9 pathways. Thus, manipulating PDCs may provide no...

Deficiencies in the incidence and function of precursor DC can be reversed with successful renal transplantation achieving normal renal function. However, the finding of reduced incidence of circulating prePDC in the peripheral blood in RT recipients may be of significance in the pathogenesis of infections and malignancies.

Porous silicon nanoparticles (pSiNP), modified to target dendritic cells (DC), provide an alternate strategy for the delivery of immunosuppressive drugs. Here, we aimed to develop a DC-targeting pSiNP displaying c-type lectin, dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), and CD11c monoclonal antibodies. The in vivo tracking of these fluorescent DC-targeting nanoparticles was assessed in both C57BL/6 mice and common marmosets ( Callithrix jacchus) by intravenous injection (20 mg/kg). Rapamycin and ovalbumin (OVA) peptide loaded pSiNP were employed to evaluate their ability to generate murine CD4CD25FoxP3 regulatory T-cells in vivo within OVA sensitized mice. In vivo, pSiNP migrated to the liver, kidneys, lungs, and spleen in both mice and marmosets. Flow cytometry confirmed pSiNP uptake by splenic and peripheral blood DC when functionalized with targeting antibodies. C57BL/6 OVA sensitized mice injected with CD11c-pSiNP loaded with rapamycin + OVA produced a 5-fold higher number of splenic regulatory T-cells compared to control mice, at 40 days post-pSiNP injection. These results demonstrate the importance of the immobilized targeting antibodies to enhance cellular uptake and enable the in vivo generation of splenic regulatory T-cells.

SummaryDendritic cells (DC) and regulatory T cells (Tregs) are vital to the development of transplant tolerance. Curcumin is a novel biological agent extracted from Curcuma longa (turmeric), with anti-inflammatory and anti-oxidant activity mediated via nuclear factor (NF)-kB inhibition. We investigated the immunomodulatory effects of curcumin on human monocyte-derived and murine DC. Human monocyte-derived DC (hu-Mo-DC) were generated in the presence (CurcDC) or absence (matDC) of 25 mM curcumin, and matured using lipopolysaccharide (1 mg/ml). DC phenotype and allostimulatory capacity was assessed. CD11c+ DC were isolated from C57BL/6 mice, pretreated with curcumin and injected into BALB/c mice, followed by evaluation of in vivo T cell populations and alloproliferative response. Curcumin induced DC differentiation towards maturation-arrest. CurcDC demonstrated minimal CD83 expression (<2%), down-regulation of CD80 and CD86 (50% and 30%, respectively) and reduction (10%) in both major histocompatibility complex (MHC) class II and CD40 expression compared to matDC. CurcDC also displayed decreased RelB and interleukin (IL)-12 mRNA and protein expression. Functionally, CurcDC allostimulatory capacity was decreased by up to 60% (P < 0·001) and intracellular interferon (IFN-g) expression in the responding T cell population were reduced by 50% (P < 0·05). T cell hyporesponsiveness was due to generation of CD4 + CD25 hi CD127 lo forkhead box P3 (FoxP3) + Tregs that exerted suppressive functions on naïve syngeneic T cells, although the effect was not antigen-specific. In mice, in vivo infusion of allogeneic CurcDC promoted development of FoxP3 + Tregs and reduced subsequent alloproliferative capacity. Curcumin arrests maturation of DC and induces a tolerogenic phenotype that subsequently promotes functional FoxP3 + Tregs in vitro and in vivo.