Dendritic Cells Crosspresent Antigens from Live B16 Cells More Efficiently than from Apoptotic Cells and Protect from Melanoma in a Therapeutic Model

Dendritic cells (DC) are able to elicit anti-tumoral CD8+ T cell responses by cross-presenting exogenous antigens in association with major histocompatibility complex (MHC) class I molecules. Therefore they are crucial actors in cell-based cancer immunotherapy. Although apoptotic cells are usually considered to be the best source of antigens, live cells are also able to provide antigens for cross-presentation by DC. We have recently shown that prophylactic immunotherapy by DC after capture of antigens from live B16 melanoma cells induced strong CD8+ T-cell responses and protection against a lethal tumor challenge in vivo in C57Bl/6 mice. Here, we showed that DC cross-presenting antigens from live B16 cells can also inhibit melanoma lung dissemination in a therapeutic protocol in mice. DC were first incubated with live tumor cells for antigen uptake and processing, then purified and irradiated for safety prior to injection. This treatment induced stronger tumor-specific CD8+ T-cell responses than treatment by DC cross-presenting antigens from apoptotic cells. Apoptotic B16 cells induced more IL-10 secretion by DC than live B16 cells. They underwent strong native antigen degradation and led to the expression of fewer MHC class I/epitope complexes on the surface of DC than live cells. Therefore, the possibility to use live cells as sources of tumor antigens must be taken into account to improve the efficiency of cancer immunotherapy

Heat Source Processing for Localized Deformation With Non-Constant Thermal Conductivity. Application to Superelastic Tensile Tests of NiTi Shape Memory Alloys

International audienceThis paper presents a methodology for heat source estimation when thermal conductivity is not constant. Both thermal and kinematic field measurements are necessary. The method requires spatiotemporal synchronization of these fields and a possible method to achieve this is presented. Temperature and heat source fields can then be properly estimated at every material points in the reference or deformed configurations of the tested sample. The proposed method also highlights the importance of precise determination of thermophysical properties in heat estimations. The method is applied for heat source estimation during a superelastic tensile test of a NiTi shape memory alloy displaying both stress-induced phase transformation and deformation localization. Spatiotemporal change in thermal conductivity occurs during deformation of this material. Typical heat source distribution results observed during mechanical tests are given. Heat sources are integrated over time, at each material point, for local estimation of heat energy associated with stress-induced phase transformation. Such a measurement can be qualified as a first step towards an in situ local DSC during a mechanical test. It is shown that the spatiotemporal distributions of these energy fields correlate well with strain field distributions during superelastic localized deformation

Image processing to estimate the heat sources related to phase transformations durint tensile test of NiTi tubes

International audienceTemperature and strain fields have been observed during superelastic tensile tests on NiTi tubes. They show strong localisations that take the shape of helical bands with characteristics that depend on global tensile strain and strain rate. To obtain quantitative energy information, allowing a better recognition of the deformation mechanisms involved inside and outside the helical bands, an estimation of the local heat sources based on image processing of the temperature fields is proposed in the present paper. This processing method is first calibrated and validated on numerically simulated temperature fields calculated using theoretical heat sources close to those associated with martensitic phase transformation. It is then applied to experimentally observed temperature fields during a typical superelastic tensile test of an NiTi tube

Experimental characterization of NiTi SMAs thermomechanical behaviour using temperature and strain full-field measurements

International audienceThe tension behaviour of initially austenitic NiTi thin wall tubes was investigated using measurements of temperature and strain fields simultaneously. The first specimen was totally superelastic but the unloading was performed before the end of the loading stress plateau. The second specimen loading was performed beyond the stress plateau to allow analyzing the unloading, but was not superelastic and at a faster strain rate. Both tests show homogeneous behaviour at the beginning of the loading. Strong localisations, taking the shape of helical bands, are observed during the loading and unloading stress plateaus. To obtain quantitative energy information, allowing a better recognition of the deformation mechanisms, an estimation of the local heat sources based on image processing of the temperature fields is presented. Two methods of heat sources estimation allowing analysis of deformation mechanisms are proposed in the present paper: first during the homogeneous, then during localized stages

Temperature full-field measurement and heat sources estimation during superelastic tests of NiTi samples

International audienc

Physical mechanisms of the deformation of a polycrystalline Ni-Ti thin tube under tension studied through full-field measurements

International audienc

Is the tensile test relevant to characterize NiTi shape memory alloy behaviour?

International audienc

Strain and thermal Heterogeneities analyse during superelastic deformation of polycrystalline NiTi tube

International audienceDue to their superelasticity properties and to their good biocompatibility, NiTi ShapeMemory Alloys (SMA) are being increasingly used for in biomedical applications. Thedesign of these applications is mostly based on modelling obtained on simple tensile tests supposed to be homogeneous [Auricchio and Sacco 2001]. The tension behaviour of an initially austenitic NiTi thin wall tube was investigated at several temperatures by having a fluid circulating inside the tube. Thermal as well as kinematical full-field measurements [Louche et al 2005] have been simultaneously carried out by using respectively infrared camera and image correlation on images captured with a visible camera. These two techniques used simultaneously allow to quantitatively observe the localisation during superelasticity (strain mechanism via martensite transformation) and therefore to characterize the geometric nature of the localisation (type, position, orientation, intensity, kinetic …). They contribute therefore to analyse the physical mechanism origin of these heterogeneities depending on the mode of deformation, velocity of the solicitation, and thermal condition during the tensile test. It has been observed that the strain field which is localised can have different morphologies (band, front…) and that the macroscopic tube’s mechanical behaviour depends on its temperature but also on the localisation morphology types. Link between total displacement of the sample, tension force, propagation speed of the front, and strain jump between each part of the front will be presented. [no pdf

Homogeneous and heterogeneous deformation mechanisms in an austenitic polycrystalline Ti-50.8 at% Ni thin tube under tension. Investigation via temperature and strain fields measurements

International audienceAn initially austenitic polycrystalline Ti-50.8 at.% Ni thin-walled tube with small grain sizes has been deformed under tension in air at ambient temperature and moderate nominal axial strain rate. Temperature and strain fields were measured using visible-light and infra-red digital cameras. In a first apparently elastic deformation stage, both strain and temperature fields are homogeneous and increase in tandem. This stage is followed by initiation, propagation and growth of localized helical bands inside which strain and temperature increases are markedly higher than in the surrounding regions. During the first apparently elastic stage of the unloading, both strain and temperature fields are homogeneous and decrease. The temperature and strain fields evolutions are then analysed in order to determine the deformation mechanisms (types and extents of phase transformations, variants (de)twinning, macroscopic banding) involved during the homogeneous and heterogeneous stages of deformation throughout the whole tube. The findings have significant implications for the understanding and modelling of superelastic behaviour of NiTi shape memory alloys