Voltammetric study of aminopurines on pencil graphite electrode in the presence of copper ions

Electrochemical oxidations of aminopurines (adenine, 2-aminopurine, 2,6-diaminopurine) and their complexes with Cu(I) on a pencil graphite electrode were investigated by means of linear sweep voltammetry (LSV) and elimination voltammetry with linear scan (EVLS). The anodic process of the Cu(I)-aminopurine complex, corresponding to the oxidation of Cu(I) to Cu(II), takes place in the potential range between 0.4 and 0.5 V (vs. Ag/AgCl/3 M KCl). At more positive potentials the aminopurines provide voltammetric peaks resulting from the oxidation of the purine ring. The stability of the accumulated complex layer was investigated by the adsorptive transfer stripping technique. © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim

CD207(+) Langerhans cells constitute a minor population of skin-derived antigen-presenting cells in the draining lymph node following exposure to Schistosoma mansoni

Infectious cercariae of Schistosoma mansoni gain entry to the mammalian host through the skin where they induce a transient inflammatory influx of mononuclear cells. Some of these cells have antigen-presenting cell function (MHCII(+)) and have been reported to migrate to the skin-draining lymph nodes (sdLN) where they have the potential to prime CD4(+) cells of the acquired immune response. Here, in mice exposed to vaccinating radiation-attenuated schistosome larvae, which induce high levels of protective immunity to challenge infection, we describe the parasite-induced migration of Langerhans cells (LCs) from the epidermal site of immunisation to the sdLN using a specific monoclonal antibody that recognises langerin (CD207). CD207(+) cells with dendritic morphology were abundant in the epidermis at all times and their migration into the dermis was detected soon after vaccination. All CD207(+) LCs were MHCII(+) but not all MHCII(+) cells in the skin were CD207(+). LCs migrated from the dermis in enhanced numbers after vaccination, as detected in dermal exudate populations recovered after in vitro culture of skin biopsies. Elevated numbers of CD207(+) LCs were also detected in the sdLN from 24 h to 4 days after vaccination. However, compared with other dermal-derived antigen-presenting cells that were CD207(−)MHCII(+) or CD207(−)CD11c(+), the relative numbers of CD207(+) cells in the dermal exudate population and in the sdLN were very small. Furthermore, the migration of CD207(+) cells after exposure to ‘protective’ radiation-attenuated, compared with ‘non-protective’ normal cercariae, was similar in terms of numbers and kinetics. Together, these studies suggest that CD207(+) LCs are only a minor component of the antigen-presenting cell population that migrates from the epidermis and they are unlikely to be important in the priming of protective CD4(+) cells in the sdLN

Enzyme-Amplified Electrochemical Detection of DNA Using Electrocatalysis of Ferrocenyl-Tethered Dendrimer

We have developed a sandwich-type enzyme-linked DNA sensor as a new electrochemical method to detect DNA hybridization. A partially ferrocenyl-tethered poly(amidoamine) dendrimer (Fc-D) was used as an electrocatalyst to enhance the electronic signals of DNA detection as well as a building block to immobilize capture probes. Fc-D was immobilized on a carboxylic acid-terminated selfassembled monolayer (SAM) by covalent coupling of unreacted amine in Fc-D to the acid. Thiolated capture probe was attached to the remaining amine groups of Fc-D on the SAM via a bifunctional linker. The target DNA was hybridized with the capture probe, and an extension in the DNA of the target was then hybridized with a biotinylated detection probe. Avidin-conjugated alkaline phosphatase was bound to the detection probe and allowed to generate the electroactive label, p-aminophenol, from p-aminophenyl phosphate enzymatically. p-Aminophenol diffuses into the Fc-D layer and is then electrocatalytically oxidized by the electronic mediation of the immobilized Fc-D, which leads to a great enhancement in signal. Consequently, the amount of hybridized target can be estimated using the intensity of electrocatalytic current. This DNA sensor exhibits a detection limit of 20 fmol. Our method was also successfully applied to the sequenceselective discrimination between perfectly matched and single-base mismatched target oligonucleotides. The DNA microarray approach has become increasingly important in basic research into the genetics of disease and also in the more practical applications of medical diagnosis and treatment. Various methods have been used to detect sequenceselective DNA hybridization, including optical, 1,2 electrochemical, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and piezoelectric transduction techniques. 20,21 Of these techniques, the electrochemical method has attracted particular attention because of its high sensitivity, low cost, and compatibility with microfabrication technology. The recent developments of electrochemical DNA biosensor have been reviewed in several reports. [3][4][5][6] Korri-Youssoufi et al. developed a method for direct, label-free, electrical DNA detection. In this approach, the electrical signal is monitored by changes in the conductivity of conducting polymer molecular interfaces, for example, using DNA-substituted or -doped polypyrrole films. 7 Thorp's group has developed a method for the detection of nucleic acids based on the electrochemical oxidation of guanine in target DNA with the mediator Ru(bpy) 3 3+

Multiple helminth infection of the skin causes lymphocyte hypo-responsiveness mediated by Th2 conditioning of dermal myeloid cells

Infection of the mammalian host by schistosome larvae occurs via the skin, although nothing is known about the development of immune responses to multiple exposures of schistosome larvae, and/or their excretory/secretory (E/S) products. Here, we show that multiple (4x) exposures, prior to the onset of egg laying by adult worms, modulate the skin immune response and induce CD4(+) cell hypo-responsiveness in the draining lymph node, and even modulate the formation of hepatic egg-induced granulomas. Compared to mice exposed to a single infection (1x), dermal cells from multiply infected mice (4x), were less able to support lymph node cell proliferation. Analysis of dermal cells showed that the most abundant in 4x mice were eosinophils (F4/80(+)MHC-II(-)), but they did not impact the ability of antigen presenting cells (APC) to support lymphocyte proliferation to parasite antigen in vitro. However, two other cell populations from the dermal site of infection appear to have a critical role. The first comprises arginase-1(+), Ym-1(+) alternatively activated macrophage-like cells, and the second are functionally compromised MHC-II(hi) cells. Through the administration of exogenous IL-12 to multiply infected mice, we show that these suppressive myeloid cell phenotypes form as a consequence of events in the skin, most notably an enrichment of IL-4 and IL-13, likely resulting from an influx of RELMa-expressing eosinophils. We further illustrate that the development of these suppressive dermal cells is dependent upon IL-4Ra signalling. The development of immune hypo-responsiveness to schistosome larvae and their effect on the subsequent response to the immunopathogenic egg is important in appreciating how immune responses to helminth infections are modulated by repeated exposure to the infective early stages of development