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Introduction: Neutrophils are a pivotal cell type in the K/BxN mouse model of rheumatoid arthritis and play an essential role in the progression of the arthritis. They are readily activated by immune complexes (ICs) via their FcγRs to release IL-1β in addition to other cytokines, which are inducing cartilage destruction. Neutrophils also release neutrophil-active chemokines to recruit themselves in an autocrine manner to perpetuate tissue destruction. FcγR-expression on neutrophils is of crucial importance for the recognition of ICs. Methods: In this study, due to its high avidity for binding to FcγRs, we investigated the potential anti-inflammatory effect of a recombinant IgG1 Fc hexamer (rFc-µTP-L309C) on neutrophils in the K/BxN mouse model of endogenously generated chronic arthritis. 200 mg/kg rFc-µTP-L309C and human serum albumin (HSA), used as controls, were administered subcutaneously every other day. Mouse ankle joints were monitored daily to generate a clinical score. Immunohistology was used to evaluate neutrophil infiltration and TUNEL to assess apoptosis. ELISA was used to measure IL-1β. Results: Treatment with rFc-µTP-L309C, but not HSA, was able to significantly ameliorate the arthritis in the K/BxN mice. Significant neutrophil infiltration into the ankle joint was found, but treatment with rFc-µTP-L309C resulted in significantly less neutrophil infiltration. There was no significant influence of rFc-µTP-L309C on neutrophil death or apoptosis. Less neutrophil infiltration could not be correlated to chemokine-mediated migration. Significantly less IL-1β was measured in mice treated with rFc-µTP-L309C. Conclusion: In the endogenous K/BxN mouse model of rheumatoid arthritis, amelioration can be explained in part by inhibition of neutrophil infiltration into the joints as well as inhibition of IL-1β production. Given the observed inhibitory properties on neutrophils, rFc-µTP-L309C may be a potential therapeutic candidate to treat autoimmune and inflammatory conditions in which neutrophils are the predominant cell type involved in pathogenesis.

Recombinant Fc-μTP-L309C is more efficacious than intravenous immunoglobulin (IVIg) at ameliorating antibody-mediated autoimmune diseases through its effects on Fcγ receptors (FcγRs). Fc-μTP-L309C inhibited in-vitro FcγR-mediated phagocytosis 10

Background High-dose intravenous immunoglobulin (IVIg), and more recently, subcutaneously-delivered Ig (SCIg), are used to treat a variety of autoimmune diseases; however, there are challenges associated with product production, availability, access and efficacy. These challenges have provided incentives to develop a human recombinant Fc as a more potent alternative to IVIg and SCIg for the treatment of autoimmune diseases. Recently, a recombinant human IgG1 Fc hexamer (Fc-μTP-L309C) was shown to be more efficacious than IVIg in a variety of autoimmune mouse models. We have now examined its efficacy compared to IVIg and SCIg in the K/BxN mouse model of endogenous, chronic rheumatoid arthritis (RA). Result Using the serum-transfer K/BxN model and the endogenous autoimmune model, amelioration of the arthritis was achieved. Effective treatment required high and frequent doses of IVIg, SCIg and Fc-μTP-L309C. However, Fc-μTP-L309C was efficacious at 10-fold lower doses that IVIg/SCIg. Also, arthritis could be prevented when Fc-μTP-L309C was given prior to onset of the arthritis in both the endogenous model and in the serum transfer model. Conclusions Our results show that Fc-μTP-L309C is a powerful treatment for the prevention and amelioration of severe, chronic arthritis in a true autoimmune mouse model of RA. Thus, the K/BxN endogenous arthritis model should be useful for testing potential therapeutics for RA. Our findings provide rationale for further examination of the treatment efficacy of immunoglobulin-based therapeutics in rheumatoid arthritis.

Small-molecule immunosuppressive drugs (ISD) prevent graft rejection mainly by inhibiting T lymphocytes. Therapeutic immunoglobulins (IVIg) are used for substitution, antibody-mediated rejection (AbMR) and HLA-sensitized recipients by targeting distinct cell types. Since the effect of ISD and IVIg on natural killer (NK) cells remains somewhat controversial in the current literature, the aim of this comparative study was to investigate healthy donor's human NK cell functions after exposure to ISD and IVIg, and to comprehensively review the current literature. NK cells were incubated overnight with IL2/IL12 and different doses and combinations of ISD and IVIg. Proliferation was evaluated by 3[H]-thymidine incorporation; phenotype, degranulation and interferon gamma (IFNγ) production by flow cytometry and ELISA; direct NK cytotoxicity by standard 51[Cr]-release and non-radioactive DELFIA assays using K562 as stimulator and target cells; porcine endothelial cells coated with human anti-pig antibodies were used as targets in antibody-dependent cellular cytotoxicity (ADCC) assays. We found that CD69, CD25, CD54, and NKG2D were downregulated by ISD. Proliferation was inhibited by methylprednisolone (MePRD), mycophenolic acid (MPA), and everolimus (EVE). MePRD and MPA reduced degranulation, MPA only of CD56bright NK cells. MePRD and IVIg inhibited direct cytotoxicity and ADCC. Combinations of ISD demonstrated cumulative inhibitory effects. IFNγ production was inhibited by MePRD and ISD combinations, but not by IVIg. In conclusion, IVIg, ISD and combinations thereof differentially inhibit NK cell functions. The most potent drug with an effect on all NK functions was MePRD. The fact that MePRD and IVIg significantly block NK cytotoxicity, especially ADCC, has major implications for AbMR as well as therapeutic strategies targeting cancer and immune cells with monoclonal antibodies.

Intravenous human immunoglobulin G (IVIG) may have therapeutic benefit in neuromyelitis optica spectrum disorders (herein called NMO), in part because of the anti-inflammatory properties of the IgG Fc region. Here, we evaluated recombinant Fc hexamers consisting of the IgM μ-tailpiece fused with the Fc region of human IgG1. In vitro, the Fc hexamers prevented cytotoxicity in aquaporin-4 (AQP4) expressing cells and in rat spinal cord slice cultures exposed to NMO anti-AQP4 autoantibody (AQP4-IgG) and complement, with >500-fold greater potency than IVIG or monomeric Fc fragments. Fc hexamers at low concentration also prevented antibody-dependent cellular cytotoxicity produced by AQP4-IgG and natural killer cells. Serum from rats administered a single intravenous dose of Fc hexamers at 50 mg/kg taken at 8 h did not produce complement-dependent cytotoxicity when added to AQP4-IgG-treated AQP4-expressing cell cultures. In an experimental rat model of NMO produced by intracerebral injection of AQP4-IgG, Fc hexamers at 50 mg/kg administered before and at 12 h after AQP4-IgG fully prevented astrocyte injury, complement activation, inflammation and demyelination. These results support the potential therapeutic utility of recombinant IgG1 Fc hexamers in AQP4-IgG seropositive NMO.

Dysregulation of endoplasmic reticulum (ER stress) has been reported in IPF patients. ER stress leads to improper wound healing and unfolded protein response. Chronic inflammation, exacerbation and progressive lung destruction are characteristics of IPF leading to a protease/anti-protease imbalance. Therefore, use of specific inhibitor of neutrophil elastase Alpha1-Antitrypsin (AAT) may be a promising approach in IPF. We investigate the effect of AAT on ER stress in IPF. AEC from IPF lung were treated with various concentration of AAT, supernatant was evaluated for IL-6, IL-8, TGF-β and mRNA for ER stress markers: GRP78, spliced XBP-1 andCHOP. For wound healing experiments A549 and B2B cell lines were treated with different concentrations of AAT in a standard scratch assay test in vitro. AEC from IPF patients are under ER stress. AAT significantly inhibits ER stress induction at mRNA level of Grp78 (1.95±0.15) vs control (5.85±0.05), and CHOP (0.93±0.04) vs control (3.75±0.32) but not in spliced XBP-1 form in the IPF primary cells. Cytokine release of pro-inflammatory and pro-fibrotic marker: IL-6 (142.1±5.28) vs (386.2±107.0) in control, IL-8 (273.3±43.12) vs (614.6±103.3) in control and TGF-β (26.31±0.30) vs (68.53±1.83) in control, were abolished by treatment with AAT. We observed improved wound repair in human alveolar epithelial A549 and human bronchial epithelial B2B cell line in response to AAT treatment in our scratch assay. AEC from IPF patients are under ER stress. ER stress pathways may serve as important therapeutic targets in IPF. AAT reduces ER stress pro-inflammatory and pro-fibrotic mediators in primary AEC.

Activation of Fc receptors and complement by immune complexes is a common important pathogenic trigger in many autoimmune diseases and so blockade of these innate immune pathways may be an attractive target for treatment of immune complex-mediated pathomechanisms. High-dose IVIG is used to treat autoimmune and inflammatory diseases, and several studies demonstrate that the therapeutic effects of IVIG can be recapitulated with the Fc portion. Further, recent data indicate that recombinant multimerized Fc molecules exhibit potent anti-inflammatory properties. In this study, we investigated the biochemical and biological properties of an rFc hexamer (termed Fc-μTP-L309C) generated by fusion of the IgM μ-tailpiece to the C terminus of human IgG1 Fc. Fc-μTP-L309C bound FcγRs with high avidity and inhibited FcγR-mediated effector functions (Ab-dependent cell-mediated cytotoxicity, phagocytosis, respiratory burst) in vitro. In addition, Fc-μTP-L309C prevented full activation of the classical complement pathway by blocking C2 cleavage, avoiding generation of inflammatory downstream products (C5a or sC5b-9). In vivo, Fc-μTP-L309C suppressed inflammatory arthritis in mice when given therapeutically at approximately a 10-fold lower dose than IVIG, which was associated with reduced inflammatory cytokine production and complement activation. Likewise, administration of Fc-μTP-L309C restored platelet counts in a mouse model of immune thrombocytopenia. Our data demonstrate a potent anti-inflammatory effect of Fc-μTP-L309C in vitro and in vivo, likely mediated by blockade of FcγRs and its unique inhibition of complement activation.

In recent years, there has been a surge in the research and development of novel molecules as potential therapeutic alternatives to traditional treatments (such as intravenous immunoglobulins) for autoimmune disorders. The aim of this review is to describe different drug development strategies and evaluate how various molecules have performed in clinical trials to date. Broadly, three main approaches have been pursued. Recombinant fragment crystallisable (rFc) multimers primarily target Fcγ receptors (FcγRs) but may also affect the complement system. These include PF-06755347 (GL-2045), CSL730 (M230), CSL777 and Pan Fc Receptor Interacting Molecule (PRIM). Neonatal Fc receptor (FcRn)-targeting therapeutics block the FcRn receptor and are represented by candidate drugs such as the Fc fragment efgartigimod and the monoclonal antibodies rozanolixizumab (UCB7665), M281 and SYNT001. Finally, Fc and FcγR-targeting therapeutics, comprise molecules that target the Fc of IgG, such as the recombinant soluble FcγIIb receptor valziflocept (SM101/SHP652) and various monoclonal antibodies directed against the receptors. The developmental status of these three classes of molecules ranges from preclinical to ongoing phase 3 clinical studies. Efgartigimod and rozanolixizumab are the most advanced and have demonstrated encouraging results from phase 2 trials in immune thrombocytopenia and myasthenia gravis. Although initial results are promising, further long-term data and a better understanding of the unique mechanisms of action of the different molecules are needed. The efficacy, safety, convenience of administration, duration of effects, and cost will all contribute to determining which of the molecules will be successful in the clinic.

Objective Ischemia-reperfusion (I/R) injury is a major clinical problem linked to vascular surgery. Currently, no drugs to prevent or to treat I/R injury are approved for clinical use. C1 inhibitor (C1 INH) is known to reduce activation of the plasma cascade systems that are involved in the pathophysiologic process of I/R injury. The aim of this study was therefore to investigate the effect of C1 INH on complement deposition and endothelial cell activation in a rat model of hind limb I/R injury. Methods Male Wistar rats (wild type, bred at the central animal facility, University of Bern), weighing 250 to 320 g, were used. The rats underwent 2-hour ischemia and 24-hour reperfusion by unilateral clamping of the femoral artery and additional use of a tourniquet. Five groups were divided according to intravenous treatment 5 minutes before ischemia: 50 IU/kg C1 INH (n = 5); 100 IU/kg C1 INH (n = 7); vehicle control (n = 5); nontreated control (n = 7); and normal, healthy control without intervention (n = 4). At the end, muscle edema, tissue viability, and histologic features were assessed. Deposition of immunoglobulin M, C1r, C4d, and fibrin and expression of plasminogen activator inhibitor 1, heparan sulfate (HS), E-selectin, and vascular cell adhesion molecule 1 were evaluated by fluorescence staining. In addition, high-mobility group box 1 protein was measured in plasma. Results Edema formation was reduced by C1 INH at two dosages, mirrored by improved histologic injury scores and preserved muscle viability. Deposition of immunoglobulin M, C4d, and fibrin was significantly decreased by 100 IU/kg C1 INH compared with nontreated controls. Pretreatment with 100 IU/kg C1 INH also significantly reduced HS shedding and expression of plasminogen activator inhibitor 1 as well as plasma levels of high-mobility group box 1 protein. Conclusions Pretreatment with both 50 and 100 IU/kg C1 INH attenuated reperfusion injury of rat hind limbs. Pretreatment with 100 IU/kg also preserved the endothelial HS layer as well as the natural, profibrinolytic phenotype of the endothelium. Prevention of endothelial cell activation by C1 INH may therefore be a promising strategy to prevent I/R injury in the clinical setting of peripheral vascular diseases and elective surgery on extremities.

Polyclonal plasma-derived IgG is a mainstay therapeutic of immunodeficiency disorders as well as of various inflammatory autoimmune diseases. In immunodeficiency the primary function of IVIG/SCIG is to replace missing antibody specificities, consequently a diverse Fab-based repertoire is critical for efficacy. Attempts to capture the Ig repertoire and express it as a recombinant IVIG product are currently ongoing. Likewise correction of the defective genes by gene therapy has also been tried. However, both approaches are far from becoming mainstream treatments. In contrast, some of the most important effector mechanisms relevant in therapy of autoimmunity are based on the Fc-portion of IgG; they include scavenging of complement and blockade/modulation of IgG receptors (Fc gamma receptor [FcγR] or the neonatal Fc receptor [FcRn]). These effects might be achieved with appropriately formulated Fc-fragments instead of full-length IgG, as suggested by a pilot study with monomeric plasma-derived Fc in children with ITP and in Kawasaki disease in the 1990s. Since then it has been proposed that structured multimerization of Fc fragments might confer efficacy at much lower doses than with IVIG. Accordingly, various molecular strategies are currently being explored to achieve controlled Fc multimerization, e.g. by fusion of IgG1 Fc to the IgG2 hinge-region or to the IgM tail-piece. Safety considerations will be crucial in the evaluation of these new entities. In a different approach, mutant Fc fragments and monoclonal antibodies have been designed for blockade of the FcRn.

NK cells express toll-like receptors (TLR) that recognize conserved pathogen or damage associated molecular patterns and play a fundamental role in innate immunity. Low molecular weight dextran sulfate (DXS), known to inhibit the complement system, has recently been reported by us to inhibit TLR4-induced maturation of human monocyte-derived dendritic cells (MoDC). In this study, we investigated the capability of DXS to interfere with human NK cell activation triggered directly by TLR2 agonists or indirectly by supernatants of TLR4-activated MoDC. Both TLR2 agonists and supernatants of TLR4-activated MoDC activated NK cells phenotypically, as demonstrated by the analysis of NK cell activation markers (CD56, CD25, CD69, NKp30, NKp44, NKp46, DNAM-1 and NKG2D), and functionally as shown by increased NK cell degranulation (CD107a surface expression) and IFN-gamma secretion. DXS prevented the up-regulation of NK cell activation markers triggered by TLR2 ligands or supernatants of TLR4-activated MoDC and dose-dependently abrogated NK cell degranulation and IFN-gamma secretion. In summary our results suggest that DXS may be a useful reagent to inhibit the direct and indirect TLR-mediated activation of NK cells.

Endothelin-1 (ET-1) is mainly secreted by endothelial cells and acts as a potent vasoconstrictor. In addition ET-1 has also been shown to have pleiotropic effects on a variety of other systems including adaptive immunity. There are two main ET-1 receptors, ET(A) and ET(B), which have different tissue and functional distributions. Dendritic cells (DC) are pivotal antigen-presenting cells linking the innate with the adaptive immune system. DC are sentinels expressing pattern-recognition receptors, e.g. the toll-like receptors (TLR) for detecting danger signals released from pathogens or tissue injury. Here we show for the first time that stimulation of human monocyte-derived DC with exogenous as well as endogenous selective TLR4 and TLR2 agonists induces the production of ET-1 in a dose- and time-dependent manner. 'Alternative' activation of DC in the presence of 1alpha,25-dihydroxyvitamin D(3) results in a marked potentiation of the endothelin response, whereas prostaglandin E(2) or dexamethasone do not increase ET-1 production. Furthermore, chetomin, an inhibitor of the transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha), prevents TLR-mediated secretion of ET-1. Surprisingly, stimulation of human monocytes with LPS does not lead to secretion of detectable amounts of ET-1. These results suggest a role of ET-1 as an important player in human DC biology and innate immunity in general.

Low molecular weight dextran sulfate (DXS) has been reported to inhibit the classical, alternative pathway as well as the mannan-binding lectin pathway of the complement system. Furthermore, it acts as an endothelial cell protectant inhibiting complement-mediated endothelial cell damage. Endothelial cells are covered with a layer of heparan sulfate (HS), which is rapidly released under conditions of inflammation and tissue injury. Soluble HS induces maturation of dendritic cells (DC) via TLR4. In this study, we show the inhibitory effect of DXS on human DC maturation. DXS significantly prevents phenotypic maturation of monocyte-derived DC and peripheral myeloid DC by inhibiting the up-regulation of CD40, CD80, CD83, CD86, ICAM-1, and HLA-DR and down-regulates DC-SIGN in response to HS or exogenous TLR ligands. DXS also inhibits the functional maturation of DC as demonstrated by reduced T cell proliferation, and strongly impairs secretion of the proinflammatory mediators IL-1β, IL-6, IL-12p70, and TNF-α. Exposure to DXS leads to a reduced production of the complement component C1q and a decreased phagocytic activity, whereas C3 secretion is increased. Moreover, DXS was found to inhibit phosphorylation of IκB-α and activation of NF-κB. These findings suggest that DXS prevents TLR-induced maturation of human DC and may therefore be a useful reagent to impede the link between innate and adaptive immunity.

Endoplasmic Reticulum stress (ER stress) plays an important role in initiation of the inflammatory response in the lung. In the present study we investigate the effects of Alpha1-Antitrypsin (AAT) on the ER stress response, inflammation and lung epithelial wound healing.We hypothesize that AAT restores ER homeostasis and reduces inflammation in bronchial and alveolar epithelial cells. Bronchial epithelial cells B2B and alveolar epithelial-like cells A549 were treated with Tunicamycin (TN) to induce ER stress, followed by treatment AAT. ER stress markers: Grp78, XBP1 and CHOP where measured by RT PCR. ELISA was performed to measure the inflammatory markers and wound healing was measured over time. Gene expression of ER stress markers was significantly reduced after AAT treatment compared to placebo: Grp78 (49.43±16.61 vs 105.87±11.76), XBP1 (34.00±6.22 vs 107.2±24.12), CHOP (58.93±15.54 vs 297.2±39.58) in A549 cells and Grp78 (42.77±9.95 vs 789.20±9.28), XBP1 (37.33±5.114 vs 120.5±14.58), CHOP (48.93±5.53 vs 307.2±31.35) in B2B cells. Levels of IL-6 in cells treated with AAT decreased significantly in A549 (193.8±16.01 vs 1321±120.2), in B2B (193.8±16.01 vs 1388±167.3). In accordance, IL-8 decreased significantly after AAT treatment for A549 (36.17±8.78 vs 93.90±1.044) and for B2B (36.17±8.78 vs 122.3±28.55). AAT increased epithelial wound healing in ER stressed B2B and A549 cells (25%+/-SD vs 18%+/-SD). AAT treatment decreases ER stress and inflammation and improves wound repair in both alveolar epithelial and bronchial epithelial cells.

BACKGROUND Ischemia/reperfusion injury of lower extremities and associated lung damage may result from thrombotic occlusion, embolism, trauma, or surgical intervention with prolonged ischemia and subsequent restoration of blood flow. This clinical entity is characterized by high morbidity and mortality. Deprivation of blood supply leads to molecular and structural changes in the affected tissue. Upon reperfusion inflammatory cascades are activated causing tissue injury. We therefore tested preoperative treatment for prevention of reperfusion injury by using C1 esterase inhibitor (C1 INH). METHODS AND FINDINGS Wistar rats systemically pretreated with C1 INH (n = 6), APT070 (a membrane-targeted myristoylated peptidyl construct derived from human complement receptor 1, n = 4), vehicle (n = 7), or NaCl (n = 8) were subjected to 3h hind limb ischemia and 24h reperfusion. The femoral artery was clamped and a tourniquet placed under maintenance of a venous return. C1 INH treated rats showed significantly less edema in muscle (P

Complement is an essential part of the innate immune system and plays a crucial role in organ and islet transplantation. Its activation, triggered for example by ischemia/reperfusion (I/R), significantly influences graft survival, and blocking of complement by inhibitors has been shown to attenuate I/R injury. Another player of innate immunity are the dendritic cells (DC), which form an important link between innate and adaptive immunity. DC are relevant in the induction of an immune response as well as in the maintenance of tolerance. Modulation or inhibition of both components, complement and DC, may be crucial to improve the clinical outcome of solid organ as well as islet transplantation. Low molecular weight dextran sulfate (DXS), a well-known complement inhibitor, has been shown to prevent complement-mediated damage of the donor graft endothelium and is thus acting as an endothelial protectant. In this review we will discuss the evidence for this cytoprotective effect of DXS and also highlight recent data which show that DXS inhibits the maturation of human DC. Taken together the available data suggest that DXS may be a useful reagent to prevent the activation of innate immunity, both in solid organ and islet transplantation.

The reactivity of 204 monoclonal antibodies (mAb) out of 377 commercially available antibodies collected by the animal homologue group of the HLAD8 was analyzed by single colour flow cytometry. Most of these mAb were originally developed against human cell surface molecules. Fifty-eight mAb (28%) showed reactivity with spleen cells of Aotus nancymaae, a non-human primate animal model in biomedical research. Out of these 58 mAb, 22 also showed reactivity with mononuclear cells derived from rhesus macaques and cynomolgus monkeys indicating that the epitopes recognized are evolutionary conserved between human, Old and New World monkeys. This novel panel of A. nancymaae reactive mAb will increase the potential to explore complex host-pathogen interactions in non-human primate animal models, particularly in malaria vaccine research.

In the absence of suitable rodent animal models for Plasmodium falciparum malaria, the efficacy testing of asexual blood-stage vaccine candidates in Aotus nancymaae represents a tool to select between different formulations before conducting expensive human clinical trials. CpG oligonucleotides (ODN) specifically promote the production of pro-inflammatory and Th1-type cytokines and they enhance the immunogenicity of co-administered antigens. Toll like receptor 9 (TLR-9) binds directly and sequence-specifically to single-stranded un-methylated CpG-DNA mediating the biological effects of CpG ODN. We cloned and functionally characterised the TLR-9 cDNA of A. nancymaae. The cDNA encompassed 3,099 bp predicted to code for 1,032 amino acid residues. Results of homology searches to human TLR-9 suggested that the receptor is 93 and 94% identical at the nucleotide and amino acid sequence levels, respectively. Stimulation of splenocytes of A. nancymaae with CpG ODN resulted in proliferative responses in all animals analysed. FACS analysis of cultures incubated with CpG ODN 2006 indicated that the B cell marker CD20 was up-regulated consistent with B cell activation. The high level of sequence conservation of Aona-TLR-9 reinforces the suitability of A. nancymaae as animal model for malaria subunit vaccine development.

Dendritic cells (DC) are professional antigen presenting cells that represent an important link between innate and adaptive immunity. Danger signals such as toll-like receptor (TLR) agonists induce maturation of DC leading to a T-cell mediated adaptive immune response. In this study, we show that exogenous as well as endogenous inflammatory stimuli for TLR4 and TLR2 induce the expression of HIF-1alpha in human monocyte-derived DC under normoxic conditions. On the functional level, inhibition of HIF-1alpha using chetomin (CTM), YC-1 and digoxin lead to no consistent effect on MoDC maturation, or cytokine secretion despite having the common effect of blocking HIF-1alpha stabilization or activity through different mechanisms. Stabilization of HIF-1alpha protein by hypoxia or CoCl(2) did not result in maturation of human DC. In addition, we could show that TLR stimulation resulted in an increase of HIF-1alpha controlled VEGF secretion. These results show that stimulation of human MoDC with exogenous as well as endogenous TLR agonists induces the expression of HIF-1alpha in a time-dependent manner. Hypoxia alone does not induce maturation of DC, but is able to augment maturation after TLR ligation. Current evidence suggests that different target genes may be affected by HIF-1alpha under normoxic conditions with physiological roles that differ from those induced by hypoxia.

Nonhypoxic stimuli can induce the expression of hypoxia-inducible factor 1α (HIF1α). Only recently has it been demonstrated that lipopolysaccharide (LPS) induces the expression of HIF1α in macrophages and that the induction of hypoxic genes in macrophages is also Toll-like receptor 4 (TLR4)-dependent. We hypothesized that HIF1α expression is induced in dendritic cells in a TLR-dependent manner, plays a crucial role in linking the innate with the adaptive immune system and may also influence mitochondrial respiration.