Langerhans cells protect from allergic contact dermatitis in mice by tolerizing CD8+ T cells and activating Foxp3+ regulatory T cells

Allergic contact dermatitis is the most frequent occupational disease in industrialized countries. It is caused by CD8(+) T cell-mediated contact hypersensitivity (CHS) reactions triggered at the site of contact by a variety of chemicals, also known as weak haptens, present in fragrances, dyes, metals, preservatives, and drugs. Despite the myriad of potentially allergenic substances that can penetrate the skin, sensitization is relatively rare and immune tolerance to the substance is often induced by as yet poorly understood mechanisms. Here we show, using the innocuous chemical 2,4-dinitrothiocyanobenzene (DNTB), that cutaneous immune tolerance in mice critically depends on epidermal Langerhans cells (LCs), which capture DNTB and migrate to lymph nodes for direct presentation to CD8(+) T cells. Depletion and adoptive transfer experiments revealed that LCs conferred protection from development of CHS by a mechanism involving both anergy and deletion of allergen-specific CD8(+) T cells and activation of a population of T cells identified as ICOS(+)CD4(+)Foxp3(+) Tregs. Our findings highlight the critical role of LCs in tolerance induction in mice to the prototype innocuous hapten DNTB and suggest that strategies targeting LCs might be valuable for prevention of cutaneous allergy.

Minimizing side reactions in chemoenzymatic dynamic kinetic resolution: organometallic and material strategies

Chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenyl ethanol into R-1-phenylethanol acetate was investigated with emphasis on the minimization of side reactions. The organometallic hydrogen transfer (racemization) catalyst was varied, and this was observed to alter the rate and extent of oxidation of the alcohol to form ketone side products. The performance of highly active catalyst [(pentamethylcyclopentadienyl) IrCl2(1-benzyl,3-methyl-imidazol-2-ylidene)] was found to depend on the batch of lipase B used. The interaction between the bio- and chemo-catalysts was reduced by employing physical entrapment of the enzyme in silica using a sol-gel process. The nature of the gelation method was found to be important, with an alkaline method preferred, as an acidic method was found to initiate a further side reaction, the acid catalyzed dehydration of the secondary alcohol. The acidic gel was found to be a heterogeneous solid acid.

Immune reactions to Bacteroides fragilis populations with three different types of capsule in a model of infection

The survival and growth of populations of the obligately anaerobic pathogenic bacterium Bacteroides fragilis enriched for large capsules (LCs), small capsules (SCs) or an electron-dense layer (EDL; non-capsulate by light microscopy) were examined in a mouse model of infection over a minimum period of 20 d. Chambers which allowed the influx of leukocytes, but not the efflux of bacteria, were implanted in the mouse peritoneal cavity. The LC and EDL populations consistently attained viable cell densities of the order of 10(8)-10(9) c.f.u. ml-1 within 24 h, whereas the SC population did not. However, after 3 d, all three bacterial populations maintained total viable numbers of 10(8)-10(9) c.f.u. ml-1 within the chambers. LC expression was selected against within 24 h in the model, the populations becoming non-capsulate by light microscopy, whereas in the SC population expression of the SC was retained by approximately 90% of the population. The EDL population remained non-capsulate by light microscopy throughout. Lymphocytes infiltrated the chambers to an equal extent for all three B. fragilis populations and at approximately 1000 times higher concentration than chambers which contained only quarter-strength Ringer's solution. The presence of neutrophils within the chambers did not cause a decrease in the total viable bacterial count. Each population elicited antibodies specific for outer-membrane proteins and polysaccharide, as detected by immunoblotting, which cross-reacted with the other populations. Differences were observed in the immunogenicity of the outer-membrane proteins within the three populations. Neutrophils were initially the predominant cell type in the chambers, but as the total leukocyte count increased with incubation time, neutrophils were outnumbered by other leukocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Performance of density functionals for calculating barrier heights of chemical reactions relevant to astrophysics

The performance of 39 different LDA, GGA, meta-GGA, and hybrid density functionals has been evaluated, for calculating forward and reverse barrier heights of 10 gas-phase reactions involving hydrogen. The reactions are all relevant to astrochemistry. Special focus is put on the applicability of DFT for calculating the rates of corresponding surface hydrogenation reactions that are relevant to the chemistry of ice-coated interstellar grains. General trends in the performance of the density functionals for reactions involving H atoms, H-2, and OH are discussed. The OH+CO reaction is shown to be a very problematic case for DFT. The best overall performance is found for the hybrid density functionals, such as MPW1K, B97-1, B97-2, and B1B95. For several reactions, the HCTH GGA functionals and the VS98 and OLAP3 meta-GGA functionals also give results that are almost as good as those of the hybrid functionals.

Reactions of nitrogen and oxygen surface groups in nanoporous carbons under inert and reducing atmospheres

The reactions of surface functional groups have an important role in controlling conversion of char nitrogen to NOx during coal combustion. This study involved an investigation of the thermal stability and reactions of nitrogen surface functional groups in nanoporous carbons. Four suites of carbons, which were used as models for coal chars, were prepared with a wide range of nitrogen and oxygen contents and types of functional groups. The porous structures of the carbons were characterized by gas adsorption methods while chemical analysis, X-ray photoelectron spectroscopy, and X-ray near edge structure spectroscopy were used to characterize the surface functional groups. Temperature programmed desorption and temperature programmed reduction methods were used to study the reactivity of the surface functional groups during heat treatment under inert and reducing conditions. Heat treatment studies show that the order of stability of the functional groups is quaternary nitrogen > pyridinic > pyrrolic > pyridine N-oxide. Pyridine N-oxide surface groups desorb NO and form N-2 via surface reactions at low temperature. Pyrrolic and pyridinic functional groups decompose and react with surface species to give NH3, HCN, and N-2 as desorption products, but most pyrrolic groups are preferentially converted to pyridinic and quaternary nitrogen. The main desorption product is N-2. Approximately 15-40 wt % of the original nitrogen was retained in the carbons mainly as quaternary nitrogen after heat treatment to 1673 K. The results are discussed in terms of decomposition ranges for surface functional groups and reaction mechanisms of surface species.

Measuring oxygen reduction/evolution reactions on the nanoscale

The efficiency of fuel cells and metal-air batteries is significantly limited by the activation of oxygen reduction and evolution reactions. Despite the well-recognized role of oxygen reaction kinetics on the viability of energy technologies, the governing mechanisms remain elusive and until now have been addressable only by macroscopic studies. This lack of nanoscale understanding precludes optimization of material architecture. Here, we report direct measurements of oxygen reduction/evolution reactions and oxygen vacancy diffusion on oxygen-ion conductive solid surfaces with sub-10 nm resolution. In electrochemical strain microscopy, the biased scanning probe microscopy tip acts as a moving, electrocatalytically active probe exploring local electrochemical activity. The probe concentrates an electric field in a nanometre-scale volume of material, and bias-induced, picometre-level surface displacements provide information on local electrochemical processes. Systematic mapping of oxygen activity on bare and platinum-functionalized yttria-stabilized zirconia surfaces is demonstrated. This approach allows direct visualization of the oxygen reduction/evolution reaction activation process at the triple-phase boundary, and can be extended to a broad spectrum of oxygen-conductive and electrocatalytic materials.

Metal Oxide Nanoparticle Mediated Enhanced Raman Scattering and Its Use in Direct Monitoring of Interfacial Chemical Reactions

Metal oxide nanoparticles (MONPs) have widespread usage across many disciplines, but monitoring molecular processes at their surfaces in situ has not been possible. Here we demonstrate that MONPs give highly enhanced (X10(4)) Raman scattering signals from molecules at the interface permitting direct monitoring of their reactions, when placed on top of flat metallic surfaces. Experiments with different metal oxide materials and molecules indicate that the enhancement is generic and operates at the single nanoparticle level. Simulations confirm that the amplification is principally electromagnetic and is a result of optical modulation of the underlying plasmonic metallic surface by MONPs, which act as scattering antennae and couple light into the confined region sandwiched by the underlying surface. Because of additional functionalities of metal oxides as magnetic, photoelectrochemical and catalytic materials, enhanced Raman scattering mediated by MONPs opens up significant opportunities in fundamental science, allowing direct tracking and understanding of application-specific transformations at such interfaces. We show a first example by monitoring the MONP-assisted photocatalytic decomposition reaction of an organic dye by individual nanoparticles.

Laughter Induction Techniques Suitable for Generating Motion Capture Data of Laughter Associated Body Movements

Laughter is a frequently occurring social signal and an important part of human non-verbal communication. However it is often overlooked as a serious topic of scientific study. While the lack of research in this area is mostly due to laughter’s non-serious nature, it is also a particularly difficult social signal to produce on demand in a convincing manner; thus making it a difficult topic for study in laboratory settings. In this paper we provide some techniques and guidance for inducing both hilarious laughter and conversational laughter. These techniques were devised with the goal of capturing mo- tion information related to laughter while the person laughing was either standing or seated. Comments on the value of each of the techniques and general guidance as to the importance of atmosphere, environment and social setting are provided.

An in situ spatially resolved method to probe gas phase reactions through a fixed bed catalyst

A new method to spatially probe heterogeneous catalysed reactions within a packed bed of catalyst has been developed. The spatial resolution is achieved using a stationary perforated capillary coupled to a mass spectrometer while the catalyst bed is moved. The oxidation of CO promoted by H-2 over a Pd catalyst has been used to demonstrate the technique.

An in situ spatially resolved analytical technique to simultaneously probe gas phase reactions and temperature within the packed bed of a plug flow reactor

This paper reports the detailed description and validation of a fully automated, computer controlled analytical method to spatially probe the gas composition and thermal characteristics in packed bed systems. As an exemplar, we have examined a heterogeneously catalysed gas phase reaction within the bed of a powdered oxide supported metal catalyst. The design of the gas sampling and the temperature recording systems are disclosed. A stationary capillary with holes drilled in its wall and a moveable reactor coupled with a mass spectrometer are used to enable sampling and analysis. This method has been designed to limit the invasiveness of the probe on the reactor by using the smallest combination of thermocouple and capillary which can be employed practically. An 80 mu m (O.D.) thermocouple has been inserted in a 250 mu m (O.D.) capillary. The thermocouple is aligned with the sampling holes to enable both the gas composition and temperature profiles to be simultaneously measured at equivalent spatially resolved positions. This analysis technique has been validated by studying CO oxidation over a 1% Pt/Al2O3 catalyst and the spatial resolution profiles of chemical species concentrations and temperature as a function of the axial position within the catalyst bed are reported.

Low-temperature oxidation reactions of ethane over a Pt/Al2O3 catalyst

Oxidative dehydrogenation of ethane was performed under conventional microreactor and TAP reactor conditions over a Pt/Al2O3 catalyst between 100 and 600 degreesC. During TAP studies, no ethene was produced whereas under flow conditions small but significant ethene formation was observed. This is consistent with a mechanism involving the gas-phase production of ethene rather than via a surface reaction. In comparison, both hydrogen and methane formation were found under TAP conditions and the trends with temperature and surface oxide composition are interpreted in terms of successive dehydrogenation steps on the catalyst surface. It is further observed that periodic introduction of the reactants can minimize deactivation processes. (C) 2003 Elsevier Inc. All rights reserved.

A spectroscopic study of the chemistry and reactivity of SO2 on Pt{111}: Reactions with O-2, CO and C3H6

The chemisorption and reactivity of SO2 on Pt{111} have been studied by HREELS, XPS, NEXAFS and temperature-programmed desorption. At 160 K SO2 adsorbs intact at high coverages, with eta(2) S-O coordination to the surface. On annealing to 270 K, NEXAFS indicates the SO2 molecular plane essentially perpendicular to the surface. Preadsorbed O-a reacts with SO2 to yield adsorbed SO4, identified as the key surface species responsible for SO2-promoted catalytic alkane oxidation. Coadsorbed CO or propene efficiently reduce SO2 overlayers to deposit S-a, and the implications of this for catalytic systems are discussed.

The advanced glycation end product, Nepsilon-(carboxymethyl)lysine, is a product of both lipid peroxidation and glycoxidation reactions

Nepsilon-(Carboxymethyl)lysine (CML) is an advanced glycation end product formed on protein by combined nonenzymatic glycation and oxidation (glycoxidation) reactions. We now report that CML is also formed during metal-catalyzed oxidation of polyunsaturated fatty acids in the presence of protein. During copper-catalyzed oxidation in vitro, the CML content of low density lipoprotein increased in concert with conjugated dienes but was independent of the presence of the Amadori compound, fructoselysine, on the protein. CML was also formed in a time-dependent manner in RNase incubated under aerobic conditions in phosphate buffer containing arachidonate or linoleate; only trace amounts of CML were formed from oleate. After 6 days of incubation the yield of CML in RNase from arachidonate was approximately 0.7 mmol/mol lysine compared with only 0.03 mmol/mol lysine for protein incubated under the same conditions with glucose. Glyoxal, a known precursor of CML, was also formed during incubation of RNase with arachidonate. These results suggest that lipid peroxidation, as well as glycoxidation, may be an important source of CML in tissue proteins in vivo and that CML may be a general marker of oxidative stress and long term damage to protein in aging, atherosclerosis, and diabetes.