Leo Joosten
Radboud University Nijmegen, Internal Medicine, Faculty Member
Candidemia is a severe invasive fungal infection with high mortality. Recognition of Candida species is mediated through pattern recognition receptors such as Toll-like receptors (TLRs). This study assessed whether genetic variation in... more
Candidemia is a severe invasive fungal infection with high mortality. Recognition of Candida species is mediated through pattern recognition receptors such as Toll-like receptors (TLRs). This study assessed whether genetic variation in TLR signaling influences susceptibility to candidemia. Thirteen mostly nonsynonymous single nucleotide polymorphisms (SNPs) in genes encoding TLRs and signaling adaptors MyD88 and Mal/TIRAP were genotyped in 338 patients (237 white, 93 African American, 8 other race) with candidemia and 351 noninfected controls (263 white, 88 African American). The SNPs significant in univariate analysis were further analyzed with multivariable logistic regression to determine association with clinical outcomes. Functional consequences of these polymorphisms were assessed via in vitro stimulation assays. Analyses of TLR SNPs revealed that 3 TLR1 SNPs (R80T, S248N, I602S) were significantly associated with candidemia susceptibility in whites. This association was not f...
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Research Interests: Immunology, Indonesia, Adolescent, Prospective studies, Humans, and 9 moreFemale, Male, Plasma, Young Adult, Dengue, Leptospirosis, Typhoid Fever, Adult, and Interleukin
Innate immunity plays a pivotal role in obesity-induced low-grade inflammation originating from adipose tissue. Key receptors of the innate immune system including Toll-like receptors-2 and -4 (TLRs) are triggered by nutrient excess to... more
Innate immunity plays a pivotal role in obesity-induced low-grade inflammation originating from adipose tissue. Key receptors of the innate immune system including Toll-like receptors-2 and -4 (TLRs) are triggered by nutrient excess to promote inflammation. The role of other TLRs in this process is largely unknown. In addition to double-stranded viral mRNA, TLR-3 can also recognize mRNA from dying endogenous cells, a process that is frequently observed within obese adipose tissue. Here, we identified profound expression of TLR-3 in adipocytes and investigated its role during diet-induced obesity. Human adipose tissue biopsies (n=80) and an adipocyte cell-line were used to study TLR-3 expression and function. TLR-3-/- and WT animals were exposed to a high-fat diet (HFD) for 16 weeks to induce obesity. Expression of TLR-3 was significantly higher in human adipocytes compared to the non-adipocyte cells part of the adipose tissue. In vitro, TLR-3 expression was induced during differenti...
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Q fever is an infection caused by Coxiella burnetii. Persistent infection (chronic Q fever) develops in 1-5% of patients. We hypothesize that inefficient recognition of C.burnetii and/or activation of host-defense in individuals carrying... more
Q fever is an infection caused by Coxiella burnetii. Persistent infection (chronic Q fever) develops in 1-5% of patients. We hypothesize that inefficient recognition of C.burnetii and/or activation of host-defense in individuals carrying genetic variants in pattern recognition receptors or adaptors would result in an increased likelihood to develop chronic Q fever. Twenty-four single nucleotide polymorphisms (SNPs) in genes encoding TLRs, NOD-like receptor-2, αvβ3-integrin, CR3, and adaptors MyD88 and TIRAP were genotyped in 139 chronic Q fever patients and in 220 control individuals with cardiovascular risk-factors and previous exposure to C.burnetii. Associations between these SNPs and chronic Q fever were assessed by univariate logistic regression models. Cytokine production in whole blood stimulation assays was correlated to relevant genotypes. Polymorphisms in TLR1(R80T), NOD2(1007fsX1) and MYD88(-938C>A) were associated with chronic Q fever. No association was observed f...
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Acute gouty arthritis is caused by endogenously formed monosodium urate (MSU) crystals, which are potent activators of the NLRP3 inflammasome. However, to induce the release of active interleukin (IL)-1β, an additional stimulus is needed.... more
Acute gouty arthritis is caused by endogenously formed monosodium urate (MSU) crystals, which are potent activators of the NLRP3 inflammasome. However, to induce the release of active interleukin (IL)-1β, an additional stimulus is needed. Saturated long-chain free fatty acids (FFAs) can provide such a signal and stimulate transcription of pro-IL-1β. In contrast, the short-chain fatty acid butyrate possesses anti-inflammatory effects. One of the mechanisms involved is inhibition of histone deacetylases (HDACs). Here, we explored the effects of butyrate on MSU+FFA-induced cytokine production and its inhibition of specific HDACs. Freshly isolated peripheral blood mononuclear cells (PBMCs) from healthy donors were stimulated with MSU and palmitic acid (C16.0) in the presence or absence of butyrate or a synthetic HDAC inhibitor. Cytokine responses were measured with ELISA and quantitative PCR. HDAC activity was measured with fluorimetric assays. Butyrate decreased C16.0+MSU-induced produ...
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Infection with Coxiella burnetii can lead to acute and chronic Q fever. Toll-like receptor 1 (TLR1), TLR2, TLR4, TLR6, nucleotide-binding oligomerization domain receptor 1 (NOD1), NOD2, and the mitogen-activated protein kinases are... more
Infection with Coxiella burnetii can lead to acute and chronic Q fever. Toll-like receptor 1 (TLR1), TLR2, TLR4, TLR6, nucleotide-binding oligomerization domain receptor 1 (NOD1), NOD2, and the mitogen-activated protein kinases are central in the innate immune response against microorganisms, but little is known about their role in the recognition of C. burnetii in humans. Human peripheral blood mononuclear cells (PBMCs) were stimulated with C. burnetii Nine Mile and the Dutch outbreak isolate C. burnetii 3262. TLRs were inhibited using specific antibodies or antagonists. Additionally, the influence of human polymorphisms in TLRs and Nod-like receptors (NLRs) on C. burnetii-induced cytokine production was assessed. Inhibition of TLR2, p38, JNK, and ERK led to decreased cytokine responses in C. burnetii-stimulated human PBMCs. Humans with polymorphisms in TLR1 and NOD2 had reduced cytokine production, compared with humans with wild-type genotypes, after stimulation. Interestingly, po...
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Although the role of monocytes in the pathogenesis of atherosclerosis is well established, the persistent vascular inflammation remains largely unexplained. Recently, our group reported that stimulation of monocytes with various microbial... more
Although the role of monocytes in the pathogenesis of atherosclerosis is well established, the persistent vascular inflammation remains largely unexplained. Recently, our group reported that stimulation of monocytes with various microbial products can induce a long-lasting proinflammatory phenotype via epigenetic reprogramming, a process termed trained immunity. We now hypothesize that oxidized low-density lipoprotein (oxLDL) also induces a long-lasting proinflammatory phenotype in monocytes, which accelerates atherosclerosis by proinflammatory cytokine production and foam cell formation. Isolated human monocytes were exposed for 24 hours to medium or oxLDL. After washing and resting for 6 days, the cells were exposed to toll-like receptor 2 and 4 agonists. Pre-exposure to oxLDL increased mRNA expression and protein formation on toll-like receptor 2 and 4 stimulation of several proatherogenic proteins, including interleukin-6, interleukin-18, interleukin-8, tumor necrosis factor-α, ...
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Although IL-1β is the master inflammatory cytokine in the IL-1 family, after more than ten years of continuous breeding, mice deficient in IL-1β exhibit no spontaneous disease. Therefore, one concludes that IL-1β is not needed for... more
Although IL-1β is the master inflammatory cytokine in the IL-1 family, after more than ten years of continuous breeding, mice deficient in IL-1β exhibit no spontaneous disease. Therefore, one concludes that IL-1β is not needed for homeostasis. However, IL-1β-deficient mice are protected against local and systemic inflammation due to live infections, autoimmune processes, tumor metastasis and even chemical carcinogenesis. Based on a large number of preclinical studies, blocking IL-1β activity in humans with a broad spectrum of inflammatory conditions has reduced disease severity and for many, has lifted the burden of disease. Rare and common diseases are controlled by blocking IL-1β. Immunologically, IL-1β is a natural adjuvant for responses to antigen. Alone, IL-1β is not a growth factor for lymphocytes; rather in antigen activated immunocompetent cells, blocking IL-1 reduces IL-17 production. IL-1β markedly increases in the expansion of naive and memory CD4T cells in response to ch...
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Interleukin-18 (IL-18) has been recently demonstrated to improve experimental hyperphagia and insulin resistance. Paradoxically, concentrations of circulating IL-18 in obese subjects and in patients with type 2 diabetes are increased. The... more
Interleukin-18 (IL-18) has been recently demonstrated to improve experimental hyperphagia and insulin resistance. Paradoxically, concentrations of circulating IL-18 in obese subjects and in patients with type 2 diabetes are increased. The objective of this study is to provide an explanation for this paradox. We have hypothesized that cells from obese individuals or from patients with type 2 diabetes mellitus have a diminished response to stimulation with IL-18. IL-18 responsiveness was tested by stimulating blood monocytes of obese or diabetes patients with rIL-18 or microbial components. Obese individuals and patients with type 2 diabetes mellitus exhibit increased circulating concentrations of IL-18. More importantly, leukocytes isolated from obese or type 2 diabetes patients respond poorly after stimulation with IL-18, as reflected by defective interferon-gamma (IFN gamma) production. The defective response to IL-18 stimulation was accompanied by a 50% reduction in the expression...
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Atherosclerosis is characterized by a persistent inflammation of the arterial wall. Monocyte-derived macrophages are the most abundant immune cells in atherosclerotic plaques. After stimulation, monocytes can adopt a long-term... more
Atherosclerosis is characterized by a persistent inflammation of the arterial wall. Monocyte-derived macrophages are the most abundant immune cells in atherosclerotic plaques. After stimulation, monocytes can adopt a long-term proinflammatory phenotype. This nonspecific memory of innate immune cells is mediated by epigenetic reprogramming and has recently been termed "trained innate immunity." The goal of this study was to describe the potential role of trained immunity in the development of atherosclerosis and to discuss the potential clinical implications of this concept. We performed a comprehensive literature search (PubMed) on the role of epigenetic programming of histones, and of trained immunity in particular, in atherogenesis. In vitro studies demonstrate that modified LDL particles can induce a long-term proinflammatory phenotype in monocytes/macrophages by epigenetic reprogramming at the level of histone methylation. This scenario is associated with increased production of proatherogenic cytokines and chemokines and increased formation of foam cells. Preclinical evidence suggests that trained innate immunity may contribute to vascular wall inflammation in patients with risk factors for atherosclerosis. Epigenetic reprogramming is regulated by enzymes that are amenable to pharmacologic modulation. Therefore, this mechanism could be used to develop novel pharmacologic targets for the prevention or treatment of atherosclerotic vascular disease.
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Candida albicans is an opportunistic fungal pathogen that induces strong proinflammatory responses, such as IL-1β production. Much less is known about the induction of immune modulatory cytokines, such as the IL-1 receptor antagonist... more
Candida albicans is an opportunistic fungal pathogen that induces strong proinflammatory responses, such as IL-1β production. Much less is known about the induction of immune modulatory cytokines, such as the IL-1 receptor antagonist (IL-1Ra) that is the main natural antagonist of IL-1, by C. albicans. Peripheral blood mononuclear cells (PBMC) of healthy individuals were stimulated with C. albicans and different components of the fungal cell wall. The role of pathogen recognition receptors (PRRs) for the induction of IL-1β and IL-1Ra was investigated by using specific blockers or in PBMC from Dectin-1 deficient patients. C. albicans induced a strong IL-1Ra response, and this induction was primarily induced by the cell-wall component β-glucan. Blocking IL-1Ra significantly increased C. albicans β-glucan hyphae induced IL-1β and IL-6 production. Surprisingly, blocking the β-glucan receptor Dectin-1 or the downstream Syk or Raf-1 pathways only marginally reduced C. albicans-induced IL-...
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Women with a history of preeclampsia are at increased risk for future cardiovascular disease. Determination of cardiovascular biomarkers may be useful to understand the pathophysiological mechanism of cardiovascular disease development in... more
Women with a history of preeclampsia are at increased risk for future cardiovascular disease. Determination of cardiovascular biomarkers may be useful to understand the pathophysiological mechanism of cardiovascular disease development in these women. We performed an analysis in the Preeclampsia Risk EValuation in FEMales study, a retrospective cohort consisting of 339 women with a history of early preeclampsia and 332 women after normotensive pregnancy. Women attended a follow-up visit ten years after the index pregnancy. A subset of 8 different cardiovascular biomarkers was investigated, reflecting inflammatory, metabolic, thrombotic and endothelial function markers. Associations between PE and these novel biomarkers were analyzed by linear regression analysis and adjusted for traditional cardiovascular risk factors. Mean age of 671 women of the PREVFEM cohort was 39 years and women were on average 10 years post index pregnancy. Women post preeclampsia had significantly higher levels of SE-selectin (adjusted difference 4.55, 99%CI 0.37; 8.74) and PAPPA (adjusted difference 19.08; 99%CI 13.18; 24.99), whereas ApoB (adjusted difference -0.23 99%CI -0.32; -0.14) was inversely associated with preeclampsia, compared to women with a previous normotensive pregnancy. Adiponectin, leptin, sICAM-1, sVCAM-1 and PAI-1 were not different between both groups. We demonstrated an independent association of preeclampsia with SE-selectin and PAPPA (markers of vascular dysfunction), which may contribute to future cardiovascular events in women post preeclampsia. However, ApoB (an apolipoprotein) was significantly lower and could point at a protective mechanism in our PE study women.
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The study of the proinflammatory role of uric acid has focused on the effects of its crystals of monosodium urate (MSU). However, little is known whether uric acid itself can directly have proinflammatory effects. In this study, we... more
The study of the proinflammatory role of uric acid has focused on the effects of its crystals of monosodium urate (MSU). However, little is known whether uric acid itself can directly have proinflammatory effects. In this study, we investigate the priming effects of uric acid exposure on the cytokine production of primary human cells upon stimulation with gout-related stimuli. Peripheral blood mononuclear cells (PBMCs) were harvested from patients with gout and healthy volunteers. Cells were pretreated with or without uric acid in soluble form for 24 h and then stimulated for 24 h with toll-like receptor (TLR)2 or TLR4 ligands in the presence or absence of MSU crystals. Cytokine production was measured by ELISA; mRNA levels were assessed using qPCR. The production of interleukin (IL)-1β and IL-6 was higher in patients compared with controls and this correlated with serum urate levels. Proinflammatory cytokine production was significantly potentiated when cells from healthy subjects ...
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Autophagy is a central process in regulation of cell survival, cell death and proliferation and plays an important role in carcinogenesis, including thyroid carcinoma. Genetic variation in autophagy components has been demonstrated to... more
Autophagy is a central process in regulation of cell survival, cell death and proliferation and plays an important role in carcinogenesis, including thyroid carcinoma. Genetic variation in autophagy components has been demonstrated to influence the capacity to execute autophagy and is associated with disease susceptibility, progression and outcome. In the present study, we assessed whether genetic variation in autophagy genes contributes to susceptibility to develop thyroid carcinoma, disease progression and/or patient outcome. The results indicate that patients carrying the ATG5 single nucleotide polymorphisms rs2245214 have a higher probability to develop thyroid carcinoma (OR 1.85 (95% CI 1.04-3.23), P = 0.042). In contrast, no significant differences could be observed for the other genetic variants studied in terms of thyroid carcinoma susceptibility. Furthermore, none of the selected genetic variants were associated with clinical parameters of disease progression and outcome. I...
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... Closing in on Toll-like receptors and NOD-LRR proteins in inflammatory disorders. Matthijs Kramer, Leo A Joosten, Carl G Figdor, Wim B van den Berg, Timothy RDJ Radstake & Gosse J Adema † † Author for... more
... Closing in on Toll-like receptors and NOD-LRR proteins in inflammatory disorders. Matthijs Kramer, Leo A Joosten, Carl G Figdor, Wim B van den Berg, Timothy RDJ Radstake & Gosse J Adema † † Author for correspondence. Sections: ...
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Candidaemia is the fourth most common cause of bloodstream infection, with a high mortality rate of up to 40%. Identification of host genetic factors that confer susceptibility to candidaemia may aid in designing adjunctive... more
Candidaemia is the fourth most common cause of bloodstream infection, with a high mortality rate of up to 40%. Identification of host genetic factors that confer susceptibility to candidaemia may aid in designing adjunctive immunotherapeutic strategies. Here we hypothesize that variation in immune genes may predispose to candidaemia. We analyse 118,989 single-nucleotide polymorphisms (SNPs) across 186 loci known to be associated with immune-mediated diseases in the largest candidaemia cohort to date of 217 patients of European ancestry and a group of 11,920 controls. We validate the significant associations by comparison with a disease-matched control group. We observe significant association between candidaemia and SNPs in the CD58 (P = 1.97 × 10(-11); odds ratio (OR) = 4.68), LCE4A-C1orf68 (P = 1.98 × 10(-10); OR = 4.25) and TAGAP (P = 1.84 × 10(-8); OR = 2.96) loci. Individuals carrying two or more risk alleles have an increased risk for candidaemia of 19.4-fold compared with ind...
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Monocyte differentiation into macrophages represents a cornerstone process for host defense. Concomitantly, immunological imprinting of either tolerance or trained immunity determines the functional fate of macrophages and susceptibility... more
Monocyte differentiation into macrophages represents a cornerstone process for host defense. Concomitantly, immunological imprinting of either tolerance or trained immunity determines the functional fate of macrophages and susceptibility to secondary infections. We characterized the transcriptomes and epigenomes in four primary cell types: monocytes and in vitro-differentiated naïve, tolerized, and trained macrophages. Inflammatory and metabolic pathways were modulated in macrophages, including decreased inflammasome activation, and we identified pathways functionally implicated in trained immunity. β-glucan training elicits an exclusive epigenetic signature, revealing a complex network of enhancers and promoters. Analysis of transcription factor motifs in deoxyribonuclease I hypersensitive sites at cell-type-specific epigenetic loci unveiled differentiation and treatment-specific repertoires. Altogether, we provide a resource to understand the epigenetic changes that underlie innat...
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The anti-tuberculosis-vaccine Bacillus Calmette-Guérin (BCG) is the most widely used vaccine in the world. In addition to its effects against tuberculosis, BCG vaccination also induces non-specific beneficial effects against certain forms... more
The anti-tuberculosis-vaccine Bacillus Calmette-Guérin (BCG) is the most widely used vaccine in the world. In addition to its effects against tuberculosis, BCG vaccination also induces non-specific beneficial effects against certain forms of malignancy and against infections with unrelated pathogens. It has been recently proposed that the non-specific effects of BCG are mediated through epigenetic reprogramming of monocytes, a process called trained immunity. In the present study we demonstrate that autophagy contributes to trained immunity induced by BCG. Pharmacologic inhibition of autophagy blocked trained immunity induced in vitro by stimuli such as β-glucans or BCG. Single nucleotide polymorphisms (SNPs) in the autophagy genes ATG2B (rs3759601) and ATG5 (rs2245214) influenced both the in vitro and in vivo training effect of BCG upon restimulation with unrelated bacterial or fungal stimuli. Furthermore, pharmacologic or genetic inhibition of autophagy blocked epigenetic reprogra...
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Research Interests: Inflammation, Immunohistochemistry, Rheumatoid Arthritis, Macrophages, Multidisciplinary, and 15 moreOsteoarthritis, Humans, Autoimmune Disease, Mice, Animals, Male, Systemic inflammation, Disease Severity, Tumor necrosis factor-alpha, Interleukins, Joints, Erythrocyte Sedimentation Rate, Knee Joint, Prostaglandin E2, and Interleukin
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Research Interests: Engineering, Physics, Chemistry, Obesity, Biology, and 16 moreInflammation, Medicine, Multidisciplinary, Western blotting, Insulin Resistance, Adipose tissue, Humans, Insulin, Mice, Animals, Body Mass Index, PLoS one, Tumor necrosis factor-alpha, Glucose Tolerance Test, Blood Proteins, and Interleukin
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Research Interests: Inflammation, Macrophages, Gene expression, Dendritic Cells, Toll like receptor signaling, and 18 moreLipopolysaccharide, Tuberculosis, Humans, Mycobacterium tuberculosis, Steady state, Caspase, Immune system, Lipopolysaccharides, Tumor necrosis factor-alpha, Interleukins, SIGNAL PEPTIDE, Protein isoforms, Lymphocytes, Tumor Necrosis Factor–α (TNF), Gene Expression Regulation, Interleukin, Interferon gamma, and Host Defense
Research Interests: Cytokines, Membrane Proteins, Medicine, Mammals, Humans, and 17 moreFemale, Animals, Male, Candidiasis, Candida albicans, Fungal Infection, Pedigree, Dectin, Phagocytosis, New England, Deficiency, Interleukins, Onychomycosis, Deficit, Tumor Necrosis Factor–α (TNF), New England Journalof Medicine, and Interleukin
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Insulin-like growth factor-1 (IGF-1) plays a key role in regulation of chondrocyte metabolism. We examined the localization of IGF-1 binding sites on chondrocytes in cartilage from normal and experimentally induced arthritic mouse knee... more
Insulin-like growth factor-1 (IGF-1) plays a key role in regulation of chondrocyte metabolism. We examined the localization of IGF-1 binding sites on chondrocytes in cartilage from normal and experimentally induced arthritic mouse knee joints. Cryostat sections from patellar cartilage were incubated either with IGF-1 receptor antibody or biotinylated IGF-1. Subsequently confocal laser scanning microscopy was applied to compare the two staining procedures qualitatively and quantitatively. This approach allowed detailed analysis of membrane-associated and intracellular staining. Using IGF-1 receptor antibody, IGF-1 receptors were found on the cell membrane of chondrocytes in the middle and deeper cartilage zones, whereas intracellular staining was highest in chondrocytes of superficial zones. After incubation with biotinylated IGF-1, distinct membrane staining was not present and fluorescence was localized homogeneously in the middle and deeper zones but not in superficial zones. In cartilage from inflamed knee joints staining with the use of IGF-1 receptor antibody did not change significantly, whereas a pronounced increase in staining was noted with biotinylated IGF-1 in chondrocytes of the middle and deeper zones of cartilage. It is concluded that the staining patterns obtained with the use of IGF-1 receptor antibody and biotinylated IGF-1 are remarkably different, suggesting that the latter also detects IGF-binding proteins. The results suggest that joint inflammation has no consistent effect on IGF-1 receptor expression but may induce a significant upregulation of IGF-binding proteins in chondrocytes of the middle and deeper zones of cartilage.
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Human epidermis plays an important role in host defense by acting as a physical barrier and signaling interface between the environment and the immune system. Pattern recognition receptors (PRRs) are crucial to maintain homeostasis and... more
Human epidermis plays an important role in host defense by acting as a physical barrier and signaling interface between the environment and the immune system. Pattern recognition receptors (PRRs) are crucial to maintain homeostasis and provide protection during infection, but are also causally involved in monogenic auto-inflammatory diseases. This study aimed to investigate the epidermal expression of PRRs and several associated host defense molecules in healthy human skin, psoriasis, and atopic dermatitis (AD). Using microarray analysis and real-time quantitative PCR, we found that many of these genes are transcribed in normal human epidermis. Only a few genes were differentially induced in psoriasis (CLEC7A (dectin-1), Toll-like receptor (TLR) 4, and mannose receptor C type 1 (MRC1)) or AD (MRC1, IL1RN, and IL1β) compared with normal epidermis. A remarkably high expression of dectin-1 mRNA was observed in psoriatic epidermis and this was corroborated by immunohistochemistry. In cultured primary human keratinocytes, dectin-1 expression was induced by IFN-γ, IFN-α, and Th17 cytokines. Keratinocytes were unresponsive, however, to dectin-1 ligands such as β-glucan or heat-killed Candida albicans, nor did we observe synergy with TLR2/TLR5 ligands. In conclusion, upregulation of dectin-1 in psoriatic lesions seems to be under control of psoriasis-associated cytokines. Its role in the biology of skin inflammation and infection remains to be explored.