Publications by authors named "Arja de Klerk"

A large community outbreak of Q fever occurred in the Netherlands in the period 2007 to 2010. Some of the infected patients developed chronic Q fever, which typically includes pathogen dissemination to predisposed cardiovascular sites, with potentially fatal consequences. To identify the immune mechanisms responsible for ineffective clearance of Coxiella burnetii in patients who developed chronic Q fever, we compared serum concentrations of 47 inflammation-associated markers among patients with acute Q fever, vascular chronic Q fever, and past resolved Q fever.

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Hazard assessment of chemicals and pharmaceuticals is increasingly gaining from knowledge about molecular mechanisms of toxic action acquired in dedicated in vitro assays. We have developed an efficient human embryonic stem cell neural differentiation test (hESTn) that allows the study of the molecular interaction of compounds with the neural differentiation process. Within the 11-day differentiation protocol of the assay, embryonic stem cells lost their pluripotency, evidenced by the reduced expression of stem cell markers Pou5F1 and Nanog.

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Unlabelled: Worldwide, paracetamol is administered as a remedy for complaints that occur after vaccination. Recently published results indicate that paracetamol inhibits the vaccination response in infants when given prior to vaccination. The goal of this study was to establish whether paracetamol exerts similar effects in young adults.

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The concept that thresholds exist for the induction of allergic contact dermatitis by chemicals with skin sensitizing properties has been used for a quantitative risk assessment approach. In this approach the potency of skin sensitizers as determined in the Local Lymph Node Assay is used to calculate the threshold for induction of sensitization. These are then used to estimate safe exposure levels for consumers.

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Severity of respiratory syncytial virus (RSV) infection ranges widely. To what extent the local immune response is involved in RSV disease pathogenesis and which markers of this response are critical in determining disease severity is still a matter of debate. The local immune response was studied in nasopharyngeal aspirates (NPAs) during RSV infection.

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Background: Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Following RSV bronchiolitis, 50% of children develop post-bronchiolitis wheeze (PBW). Animal studies have suggested that interleukin (IL)-10 plays a critical role in the pathogenesis of RSV bronchiolitis and subsequent airway hyperresponsiveness.

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There are currently no validated animal models that can identify low molecular weight (LMW) respiratory sensitizers. The Local Lymph Node Assay (LLNA) is a validated animal model developed to detect contact sensitizers using skin exposure, but all LMW respiratory sensitizers tested so far were also positive in this assay. Discrimination between contact and respiratory sensitizers can be achieved by the assessment of cytokine profiles.

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In the Local Lymph Node Assay (LLNA), a stimulation index of 3 (SI = 3) is established as a threshold value for hazard identification of sensitization. The corresponding EC3 value, the effective concentration inducing a threefold increase compared to controls, can possibly predict threshold levels for sensitization in humans. Exposure to a dose below the threshold dose would not result in an induction of an immune response.

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The local lymph node assay (LLNA) is used to test the potential of low molecular weight (LMW) compounds to induce sensitization via the skin. In the present study, a respiratory LLNA was developed. Male BALB/c mice were exposed head/nose-only during three consecutive days for 45, 90, 180, or 360 min/day to various LMW allergens.

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Lactic acid bacteria are claimed to have immunomodulating effects. Stimulation as well as suppression of T helper (Th)1 mediated immune responses, have been described for various strains. Experiments involving Lactobacillus casei Shirota (LcS) detected mainly enhancement of innate immune responses and promotion of Th1 mediated immune reactivity.

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The application of a novel model for sunscreen photoimmunoprotection studies was assessed using a systemic infection of rats with herpes simplex virus type 1 (HSV-1). Rats were irradiated daily with 1 minimal erythemal/oedematous dose of UVB for 7 consecutive days on their shaved backs with or without application of a broad-spectrum sunscreen (containing TiO2) with a sun protection factor of 10. Subsequently, rats were infected intranasally with HSV.

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