Bystander CD4+ T cells: crossroads between innate and adaptive immunity

T cells are the central mediators of both humoral and cellular adaptive immune responses. Highly specific receptor-mediated clonal selection and expansion of T cells assure antigen-specific immunity. In addition, encounters with cognate antigens generate immunological memory, the capacity for long-term, antigen-specific immunity against previously encountered pathogens. However, T-cell receptor (TCR)-independent activation, termed “bystander activation”, has also been found. Bystander-activated T cells can respond rapidly and secrete effector cytokines even in the absence of antigen stimulation. Recent studies have rehighlighted the importance of antigen-independent bystander activation of CD4⁺ T cells in infection clearance and autoimmune pathogenesis, suggesting the existence of a distinct innate-like immunological function performed by conventional T cells. In this review, we discuss the inflammatory mediators that activate bystander CD4⁺ T cells and the potential physiological roles of these cells during infection, autoimmunity, and cancer.Subject terms: T cells, CD4-positive T cells     

Separation and preconcentration of ultratrace lead in biological organisms and its determination by graphite furnace atomic absorption spectrometry

A biological organism (chitosan) was utilized to preconcentrate lead ions from tap water. This preconcentration was achieved by mixing 0.8 ml of chitosan slurry with 10-50 ml of lead-containing solution and subsequently separating by centrifugation. The chitosan paste was then dissolved in 1 ml of 0.2% nitric acid and analysed by graphite furnace atomic absorption spectrometry. The extraction efficiency can approach 100% in the pH range 4-10. The amount of chitosan used was not critical. The effect of some impurities was also investigated. If six samples were prepared simultaneously, the time needed to preconcentrate each sample was less than 3 min. Two different modes of standard addition (the standard lead solutions being added before and after preconcentration) were used for analysis of tap water samples, and the results obtained by the two modes were found to be quite consistent.     

PEO／PBHE共混体系X射线散射研究

在聚环氧乙烷(PEO)/聚双酚A羟基醚(PBHE)共混体系中PEO是一个强质子受体,而PBHE是一个强质子给体,两者极易形成氢键,十分有利于形成互容对。笔者研究了PEO/PBHE共混体系的相容性,等温及非等温结晶动力学,本文根据Vonk提出的一维电子密度相关函数,分析了PEO/PBHE的SAXS现象,求得了共混体系的结晶度,片晶层厚度,过渡层厚度及长周期等结构参数。     

Determination of estrone and 17 beta-estradiol in human hair by gas chromatography-mass spectrometry

An efficient procedure is described for the determination of estrone and 17 beta-estradiol in hair by gas chromatography-mass spectrometry (GC-MS). The method involves alkyloxycarbonylation with isobutyl chloroformate (isoBCF) of phenolic hydroxy groups after alkaline digestion of hair samples. The resulting isobutyloxycarbonyl derivatives of estrone and 17 beta-estradiol are extracted with hexane and subjected to chlorodifluoroacetyl derivatization in order to protect the remaining alcoholic hydroxy groups. When GC-MS with selected ion monitoring (SIM) was used, the quantitative ions were at m/z 270 and 384 in the electron ionization mass spectra for estrone and 17 beta-estradiol, respectively. The detection limits for SIM of the steroids were 1 and 2 pg, respectively, and the SIM responses were linear with correlation coefficients varying from 0.991 to 0.994 in the concentration range 0.2-4.0 ng g-1 for the estrogens studied. The detection of estrone and 17 beta-estradiol in hair samples was possible in the concentration range of 0.24-1.30 ng g-1. The concentrations of the two estrogens detected were different in male and female hair samples.     

Complexometric determination of magnesium oxide in flyash blended cement

A complexometric titration method is proposed to determine magnesium oxide in flyash blended cement. A 0.50 g of sample was heated with hydrochloric acid for 10 min. The solution was diluted to 500 ml, and 50 ml was pipetted and heated to boiling with 2.5 ml of 5% ammonium oxalate solution. The solution was then made alkaline by ammonium hydroxide. The suspension was cooled and filtered. The filtrate was titrated by standard 0.002M EDTA solution. The concentration of MgO in sample was calculated. The flyash content of the sample was determined by British Standard method and the recovery factor (f) was calculated by the equation of f = 100/(99 - 0.315 x %FA). Concentration of MgO in sample was corrected by multiplying the recovery factor with concentration initially found by EDTA titration. The precision of the method is better with more time saving than the official methods.     

A novel oxygen and/or carbon dioxide-sensitive optical transducer

A novel oxygen (O(2)) and/or carbon dioxide (CO(2))-sensitive transducer for the measurement of both gaseous O(2) and CO(2) over the concentration ranges of O(2), 0-100% and CO(2), 0-10% has been described employing a solution of 10.6 muM fluorescein (FL) and 190 muM potassium hydroxide in a solvent mixtures of 1:1 (v/v) N,N'-diethylaniline (DEA) and N,N-dimethylformamide. Increasing O(2) concentrations cause the absorbance of the solution at a wavelength of 400 nm to increase owing to a contact charge transfer reaction existing between O(2) and DEA molecules, and increasing CO(2) concentrations produce a non-linear fall in absorbance at 520 nm as the colour of FL changes from its orange dianion form to the colourless neutral, lactonic form. Both processes are independent of each other and reversible. The response to changes in O(2) concentrations is in good agreement with Beer-Lambert's law and the response to changes in CO(2) concentrations in non-linear. A fibre optic sensing system based on this solvent-dye solution has been set up for continuous and reversible determination of both gaseous O(2) and CO(2). Possible applications include environmental and physiological monitoring of O(2) over the ranges of 0-100% and CO(2), 0-10%.     

Nanophase segregation and water dynamics in the dendrion diblock copolymer formed from the Fréchet polyaryl ethereal dendrimer and linear PTFE

We propose a new material consisting of a dendrion copolymer formed from (a) a water-soluble dendritic polymer and (b) a hydrophobic backbone. Using molecular dynamics simulations techniques, we determine the structure and dynamics of the dendrion formed by second-generation Fréchet polyaryl ethereal dendrimer as the hydrophilic component and linear polytetrafluoroethylene (PTFE) as the hydrophobic polymer, with 5 and 10 wt % of water. We find that this material produces a well-developed nanoscale structure in which water forms a continuous nanophase, making this new family of compounds promising candidates for applications in fuel cell membranes. We find that the water molecules are incorporated into the dendrimer block of the copolymer to form a nanophase-segregated structure. The well-developed nanophase-segregated structures rendered by this material have characteristic dimensions of segregation ( approximately 30 Angstrom) and dendrimer conformational properties that are independent of water content. Calculations of water dynamics and proton transport in these nanophase-segregated structures indicate that the dendrion copolymer membrane with 10 wt % of water content has a water structure and transport properties equivalent to that of the hydrated Nafion membrane with 20 wt % of water content.     

Dual effect of oxidative stress on NF-kappakB activation in HeLa cells

Reactive oxygen species (ROS) has been implicated as an inducer of NF-kappaB activity in numbers of cell types where exposure of cells to ROS such as H(2)O(2) leads to NF-kappaB activation. In contrast, exposure to oxidative stress in certain cell types induced reduction of tumor necrosis factor (TNF)- induced NF-kappaB activation. And various thiol-modifying agents including gold compounds and cyclopentenone prostaglandins inhibit NF-kappaB activation by blocking IkappaB kinase (IKK). To understand such conflicting effect of oxidative stress on NF- kappakB activation, HeLa cells were incubated with H(2)O(2) or diamide and TNF-induced expression of NF-kappaB reporter gene was measured. NF-kappaB activation was significantly blocked by these oxidizing agents, and the inhibition was accompanied with reduced nuclear NF-kappaB and inappropriate cytosolic IkappaB degradation. H(2)O(2) and diamide also inhibited IKK activation in HeLa and RAW 264.7 cells stimulated with TNF and lipopolysaccharide, respectively, and directly blocked IKK activity in vitro. In cells treated with H(2)O(2) alone, nuclear NF-kappaB was induced after 2 h without detectable degradation of cytosolic IkappaBalphaa or activation of IKK. Our results suggest that ROS has a dual effect on NF-kappaB activation in the same HeLa cells: it inhibits acute IKK-mediated NF-kappakB activation induced by inflammatory signals, while longer-term exposure to ROS induces NF-kappaB activity through an IKK-independent pathway.     

An organic-phase optical phenol biosensor coupling enzymatic oxidation with chemical reduction

This paper presents a recycle amplification optical biosensor to monitor phenol in hydrophobic organic solvents. Tyrosinase was first immobilised by entrapping it in a copolymer membrane of poly(vinyl alcohol)-hydroxyethyl carboxymethylcellulose doped with octadecylsilica particles. The biosensor was then constructed by co-mixing small particles of the immobilised tyrosinase with the adduct of L-ascorbic acid-poly(vinyl alcohol) (AsA-PVA) in conjunction with an optical oxygen transducer. The biosensor was characterised by its amplifying response to phenol, stable biocatalytic activity of entrapped-tyrosinase, free of interference from o-quinone polymerisation, and large water buffer capacity in hydrophobic organic solvents. The working range of the biosensor to phenol was 0.08-40 mmol dm(-3) in the flow mode. The response times (95%) of the biosensor were 4-7 min for phenol. The operational lifetime was more than 40 assays and the shelf lifetime of the biosensor was longer than 3 months. The biosensor has been successfully applied to quantify the phenol contents in some commercial ointment samples.     

Modeling of the Permeate Flux during Microfiltration of BSA-Adsorbed Microspheres in a Stirred Cell

A study on the variation of the permeate flux was performed in a stirred cell charged with microspheres, to investigate the effects of the stirrer speeds (300, 400, and 600 rpm) and the BSA concentration (0.1, 0.2, 0.4, and 0.8 g/L) under constant pressure. The permeate flux increased over time before the saturation point, but it began to decrease after that point. An increase of the BSA concentration and the stirrer speed resulted in the rapid increase of the permeate flux. This is contrary to the observation of the conventional filtration experiments using a stirred cell. A resistance-in-series model was employed for the modeling of the permeate flux. The cake resistance (R(c), induced by the concentration polarization of microspheres) and the fouling resistance (R(f), induced by the adsorption of BSA inside the membrane pore) must be considered simultaneously for the modeling. These modeling results were in good agreement with the experimental data. These can be applied to the special system considering both R(c) and R(f) as well as the general filtration systems using a stirred cell. Copyright 2000 Academic Press.