Macrophages (M ) play a central role as effector cells in immunity

The recognition of peptidoglycan by cells of the innate immune system has been controversial; both TLR2 and nucleotide-binding oligomerization domain-2 (NOD2) have been implicated in this process. In the present study we demonstrate that although NOD2 is required for recognition of peptidoglycan, this leads to strong synergistic effects on TLR2-mediated production of both pro- and anti-inflammatory cytokines. Defective IL-10 production in patients with Crohn’s disease bearing loss of function mutations of NOD2 may lead to overwhelming inflammation due to a subsequent Th1 bias. In addition to the potentiation of TLR2 effects, NOD2 is a modulator of signals transmitted through TLR4 and TLR3, but not through TLR5, TLR9, or TLR7. Thus, interaction between NOD2 and specific TLR pathways may represent an important modulatory mechanism of innate immune responses.

Objective: The aim of this study was to evaluate peak serum alanine aminotransferase (ALT) and postoperative clinical outcomes after hypothermic oxygenated machine perfusion (HOPE) versus static cold storage (SCS) in extended criteria donation (ECD) liver transplantation (LT) from donation after brain death (DBD). Background: HOPE might improve outcomes in LT, particularly in high-risk settings such as ECD organs after DBD, but this hypothesis has not yet been tested in a randomized controlled clinical trial (RCT). Methods: Between September 2017 and September 2020, 46 patients undergoing ECD-DBD LT from four centers were randomly assigned to HOPE (n = 23) or SCS (n = 23). Peak-ALT levels within 7 days following LT constituted the primary endpoint. Secondary endpoints included incidence of postoperative complications [Clavien-Dindo classification (CD), Comprehensive Complication Index (CCI)], length of intensive care- (ICU) and hospital-stay, and incidence of early allograft dysfunction (EAD). Results: Demographics were equally distributed between both groups [donor age: 72 (IQR: 59–78) years, recipient age: 62 (IQR: 55–65) years, labMELD: 15 (IQR: 9–25), 38 male and 8 female recipients]. HOPE resulted in a 47% decrease in serum peak ALT [418 (IQR: 221–828) vs 796 (IQR: 477–1195) IU/L, P = 0.030], a significant reduction in 90-day complications [44% vs 74% CD grade ≥3, P = 0.036; 32 (IQR: 12–56) vs 52 (IQR: 35–98) CCI, P = 0.021], and shorter ICU- and hospital-stays [5 (IQR: 4–8) vs 8 (IQR: 5–18) days, P = 0.045; 20 (IQR: 16–27) vs 36 (IQR: 23–62) days, P = 0.002] compared to SCS. A trend toward reduced EAD was observed for HOPE (17% vs 35%; P = 0.314). Conclusion: This multicenter RCT demonstrates that HOPE, in comparison to SCS, significantly reduces early allograft injury and improves post-transplant outcomes in ECD-DBD liver transplantation.

Dendritic cells (DC) are professional antigenpresenting cells of the immune system that play a key role in regulating T cell-based immunity. In vivo, the capacity of DC to activate T cells depends on their ability to migrate to the T cell areas of lymph nodes as well as on their maturation state. Depending on their cytokine-secreting proWle, DC are able to skew the immune response in a speciWc direction. In particular, IL-12p70 producing DC drive T cells towards a T helper 1 type response. A serious disadvantage of current clinical grade ex vivo generated monocyte-derived DC is the poor IL-12p70 production. We have investigated the eVects of Toll-like receptor (TLR)-mediated maturation on ex vivo generated human monocyte-derived DC. We demonstrate that in contrast to cytokine-matured DC, DC matured with poly(I:C) (TLR3 ligand) and/or R848 (TLR7/ 8 ligand) are able to produce vast amounts of IL-12p70, but exhibit a reduced migratory capacity. The addition of prostaglandin E 2 (PGE 2 ) improved the migratory capacity of TLR-ligand matured DC while maintaining their IL-12p70 production upon T cell encounter. We propose a novel clinical grade maturation protocol in which TLR ligands poly(I:C) and R848 are combined with PGE 2 to generate DC with both high migratory capacity and IL-12p70 production upon T cell encounter.

Summary Coxsackie B viruses (CVB) and Echoviruses (EV)form

The nucleotide oligomerization domain 2 (NOD2) 3020insC (NOD2fs) mutation increases susceptibility to Crohn's disease (CD), but the mechanism remains controversial. Loss-of-function and gain-of-function phenotypes have been described as a result of NOD2fs. Here, we show that dendritic cells (DC) derived from CD patients homozygous for this mutation respond normally to purified Toll-like receptor (TLR) ligands but fail to up-regulate the costimulatory molecules CD80 and CD86 in response to the NOD2 ligand muramyl dipeptide (MDP). Moreover, they lack MDP-induced enhancement of TLR-mediated tumor necrosis factor alpha, interleukin (IL)-12, and IL-10 production, which is observed in control DC with intact NOD2. These data indicate that the NOD2fs mutation results in a loss-of-function phenotype in human myeloid DC and imply decreased immune regulation by IL-10 as a possible mechanism for this mutation in CD.

Synthesis and release of pro-inflammatory cytokines, such as IL-1b, play a crucial role in the intestinal inflammation that characterizes Crohn's disease. Mutations in the nucleotide oligomerization domain 2 (NOD2) gene are associated with an increased risk of Crohn's disease. Although it is known that NOD2 mediates cytokine responses to muramyl dipeptide (MDP), it is yet unclear whether NOD2 stimulation mediates only transcription of pro-IL-1b mRNA, or whether NOD2 is also involved in the activation of caspase-1 and release of active IL-1b. By investigating the response of MNC from Crohn's disease patients homozygous for the 3020insC NOD2 mutation, we were able to show that NOD2 signaling after stimulation with MDP has a dual effect by activating proIL-1b mRNA transcription and inducing release of bioactive IL-1b. Because NOD2 engagement amplifies TLR stimulation, we investigated whether activation of caspase-1 by MDP is involved in the NOD2/TLR synergism. The synergy in IL-1b production between NOD2 and TLR is mediated at post-translational level in a caspase-1-dependent manner, which indirectly suggests that NOD2 also induces caspase-1 activation. In contrast, the synergy in TNF-a production after stimulation with MDP and LPS is induced at transcriptional level. This demonstrates that both caspase-1-dependent and -independent mechanisms are involved in the synergy between NOD2 and TLR.Introduction NOD-like receptors (NLR) are intracellular receptors for bacterial peptidoglycans, which complement the recognition of pathogen-associated molecular patterns (PAMP) by membrane-bound TLR [1,2]. Nucleotide oligomerization domain 2 (NOD2) is a member of the NACHT-LRR (NLR) receptor family, which recognizes muramyl dipeptide (MDP), the minimal motif of peptidoglycan of both Gram-positive and Gram-negative bacteria [3]. Mutations in the NOD2 gene are associated with Crohn's disease [4,5], but how NOD2 exactly acts in the pathogenesis of this auto-inflammatory disease is unclear [6][7][8]. Therefore, a better understanding of the intracellular events induced by the interaction between NOD2 and peptidoglycan is crucial for both the insight into recognition of Gram-positive pathogens by the innate immune system, and for the pathogenesis of the inflammatory reactions in Crohn's disease. Activation of human mononuclear cells (MNC) by MDP leads to production of pro-inflammatory cytokines, especially IL-1b [7,9]. IL-1b is produced as pro-IL-1b a 31-34-kDa inactive form of the cytokine, which is later cleaved by caspase-1 to the bioactive 17-kDa . This is followed by IL-1b excretion in microvesicles into the extracellular environment [11]. Apparently, MDP is capable of inducing all three steps, but it is unclear whether NOD2 alone or other receptors are involved in one or more of these steps of IL-1b production. It has been proposed that several of the NLR family members are able to recognize MDP, most notably NOD2, NALP3, and NALP1, and that they execute different functions necessary for cytokine production. In this concept, ...

OBJECTIVEType 1 diabetes is a chronic endocrine disorder in which enteroviruses, such as coxsackie B viruses and echoviruses, are possible environmental factors that can trigger or accelerate disease. The development or acceleration of type 1 diabetes depends on the balance between autoreactive effector T-cells and regulatory T-cells. This balance is particularly influenced by dendritic cells (DCs). The goal of this study was to investigate the interaction between enterovirus-infected human pancreatic islets and human DCs.RESEARCH DESIGN AND METHODSIn vitro phagocytosis of human or porcine primary islets or Min6 mouse insuloma cells by DCs was investigated by flow cytometry and confocal analysis. Subsequent innate DC responses were monitored by quantitative PCR and Western blotting of interferon-stimulated genes (ISGs).RESULTSIn this study, we show that both mock- and coxsackievirus B3 (CVB3)-infected human and porcine pancreatic islets were efficiently phagocytosed by human monocyte–derived DCs. Phagocytosis of CVB3-infected, but not mock-infected, human and porcine islets resulted in induction of ISGs in DCs, including the retinoic acid–inducible gene (RIG)-I–like helicases (RLHs), RIG-I, and melanoma differentiation–associated gene 5 (Mda5). Studies with murine Min6 insuloma cells, which were also efficiently phagocytosed, revealed that increased ISG expression in DCs upon encountering CVB-infected cells resulted in an antiviral state that protected DCs from subsequent enterovirus infection. The observed innate antiviral responses depended on RNA within the phagocytosed cells, required endosomal acidification, and were type I interferon dependent.CONCLUSIONSHuman DCs can phagocytose enterovirus-infected pancreatic cells and subsequently induce innate antiviral responses, such as induction of RLHs. These responses may have important consequences for immune homeostasis in vivo and may play a role in the etiology of type 1 diabetes.