Human CD25+ Regulatory T Cells Maintain Immune Tolerance to Nickel in Healthy, Nonallergic Individuals

Abstract We investigated the capacity of CD25+ T regulatory cells (Treg) to modulate T cell responses to nickel, a common cause of allergic contact dermatitis. CD4+ T cells isolated from the peripheral blood of six healthy, nonallergic individuals showed a limited capacity to proliferate in response to nickel in vitro, but responsiveness was strongly augmented (mean increment ± SD, 240 ± 60%) when cells were depleted of CD25+ Treg. Although CD25+ Treg were anergic to nickel, a small percentage up-regulated membrane CTLA-4 upon nickel exposure. CD25+ Treg strongly and dose-dependently inhibited nickel-specific activation of CD25− T lymphocytes in coculture experiments in a cytokine-independent, but cell-to-cell contact-dependent, manner. Approximately 30% of circulating CD25+ Treg expressed the cutaneous lymphocyte-associated Ag (CLA), and CLA+CD25+ Treg were more efficient than CLA−CD25+ cells in suppressing nickel responsiveness of CD25− T cells. The site of a negative patch test in response to nickel showed an infiltrate of CD4+CLA+ cells and CD25+ cells, which accounted for ∼20% of the total T cells isolated from the tissue. Skin-derived T cells suppressed nickel-specific responses of peripheral blood CD25− T cells. In addition, 60 ± 14% of peripheral blood CD25+ Treg expressed the chemokine receptor CCR7 and strongly inhibited naive T cell activation in response to nickel. Finally, CD25+ T cells isolated from peripheral blood of nickel-allergic patients showed a limited or absent capacity to suppress metal-specific CD4+ and CD8+ T cell responses. The results indicates that in healthy individuals CD25+ Treg can control the activation of both naive and effector nickel-specific T cells

High-resolution X-ray diffraction of silicon-on-nothing

High-resolution multi-crystal X-ray diffraction was employed to characterize silicon-on-nothing samples consisting of a one-dimensional periodic array of buried empty channels. p- and n-type silicon starting wafers were used for sample preparation. For the p- type samples, this periodic array gives rise to well defined Fraunhofer diffraction when the channels are normal to the scattering plane. This indicates good lattice quality of the layer containing the channels. Moreover, the lattices of the surface layer and the layer with the channels were almost indistinguishable from that of perfect silicon. Conversely, the n-type samples showed such lattice tilts and out-of-plane mosaic spreads in the surface and buried layers that Fraunhofer diffraction does not occur from the periodic array of the channels. The elucidation of this different behaviour is in progress and will most likely be fruitful after X-ray images of the same samples are taken

Physics and Art: introducing light-matter interaction by looking at famous paintings

The colour of an object is a subjective sensation produced by a series of phenomena connected to the interaction between matter and electromagnetic waves. Our eyes incessantly convey images and information to us, but hardly ever do we stop to consider their physical origin. We are enchanted by the colours of spring, we marvel at the beauty of a butterfly’s wings, we are carried away by the sight of a picture and yet we ignore that these sights are the result of the interaction between light in the environment and the material of the bodies’ surface. Such an attitude originates spontaneous explanatory hypotheses which tend to take root, such as those of colour being one of the properties of an object and light being a neutral entity which gives luminosity to objects. This position does not allow a scientific approach to reality and therefore it does not allow quantification of the phenomena. Unfortunately scientific models of phenomena often require mathematical or geometrical formalism, and therefore they are often seen by the students as being an end in themselves, having no evidence in reality and no practical use; for this reason, they may not be considered to represent an actual advance in learning.Art is probably the most suitable context to introduce the phenomena connected to light-matter interaction, since painters know well - at least from a practical point of view - that the final result of their work is given by their capability to control these phenomena

Materials science and optics in the arts: case studies to improve physics education

It is nowadays universally recognized that the training of teachers, especially primary school teachers, requires integration of the education in physics and in the psychological and pedagogical fields.Therefore, a cultural background in physics is necessary, as well as knowledge of the conceptual difficulties and of the teaching methods typical of the discipline itself. The formation in a specific field of knowledge has to provide teachers with the capability of transferring concepts.Hence the problem is how to realize a formation supplying educational tools for different situations and contexts, therefore improving teaching competences. Different educational models have been proposed, referring to teaching equipments and operational strategies in meta-cultural, experiential, or situated forms.This work moves from the assumption that pre-service training of teachers requires education in this discipline through the teaching of the discipline itself. This objective can be achieved by means of teaching activities in which the planning as well as the reflection on didactical proposals are an integral part of the teaching process. Moreover, the direct involvement is considered to be effective only when it is operative and tasks and goals to be reached are clearly defined.We have selected different strategies based on such hypotheses and characterized by putting in situation and by realizing operative involvement. Not completely defined instruments have been offered to the students because the elaboration and the planning phases are considered part of the intervention therefore integrating professional formation with disciplinary formation.The present research refers to the study of the impact of such a strategy on the initial teacher formation. The analysis is centred on the improvement of critical and planning capacities for the construction of professional competences in physics education, with particular care to the planning of single experimental activities, of explorative experimental chains and of maps and conceptual networks for the definition of paths for formal instruments management, either for personal exploration, or for didactical proposal definition

Costruire i diagrammi di fase dai dati sperimentali: una proposta didattica

In this paper an educational laboratory work on phase diagrams is presented. The phase diagrams are at the basis of many technological processes involving materials with peculiar properties to produce artifacts of our everyday life. Our proposal is a learning tool on phase transitions, based on computer on line experiments and problem solving activities. In particular it is oriented to the analysis of: a) unary pressure-temperature diagram, b) binary lens-like diagram, and c) binary eutectic diagram. The proposal is thought to gradually proceed towards increasing difficulties so that the activities can be selected and used at various levels

Interdiffusion of thin chromium and gold films deposited on silicon

The backscattering technique was used to study the interdiffusion process of Cr and Au films deposited on Si substrates. The results indicate that Au diffuses in Cr with an effective diffusion coefficient D = const. * exp(-0.68/kT). The activation energy is consistent with a diffusion process that occurs preferentially through grain boundaries. The high value of the diffusion coefficient justifies the presence of Au at the Cr-Si interface after a low-temperature short-time heat treatment. At temperature > 370°C (the eutectic point of the Si-Au system) and after a longenough heat treatment, the Au is completely mixed with Si

Characterization of Bioacceptable Carbon Materials

Bioacceptable carbon films deposited with a new low temperature technique have been investigated using Raman and X-ray photoelectron spectroscopy. Our results reveal a substantial similarity between the low temperature deposited films and the well-known bioacceptable low temperature isotropic (LTI) pyrocarbon. The Raman spectra, as well as the larger density and oxygen content in the bulk, lead to the speculation of the presence of the common tetrahedral bonds in these materials