The Blood of Healthy Individuals Exhibits CD8 T Cells with a Highly Altered TCR Vb Repertoire but with an Unmodified Phenotype

CD8 T cell clonal expansions (TCE) have been observed in elderly, healthy individuals as well in old mice, and have been associated with the ageing process. Both chronic latent and non-persistent viral infections have been proposed to drive the development of distinct non-functional and functional TCE respectively. Biases in TCR Vβ repertoire diversity are also recurrently observed in patients that have undergone strong immune challenge, and are preferentially observed in the CD8 compartment. Healthy adults can also exhibit CD8 T cells with strong alterations of their CDR3 length distribution. Surprisingly, no specific investigations have been conducted to analyze the CD8 T cell repertoire in normal adults, to determine if such alterations in TCR Vβ repertoire share the features of TCE. In this study, we characterized the phenotype and function of the CD8 population in healthy individuals of 25–52 years of age. All but one of the EBV-positive HLA-B8 healthy volunteers that were studied were CMV-negative. Using a specific unsupervised statistical method, we identified Vβ families with altered CDR3 length distribution and increased TCR Vβ/HPRT transcript ratios in all individuals tested. The increase in TCR Vβ/HPRT transcript ratio was more frequently associated with an increase in the percentage of the corresponding Vβ+ T cells than with an absence of modification of their percentage. However, in contrast with the previously described TCE, these CD8+ T cells were not preferentially found in the memory CD8 subset, they exhibited normal effector functions (cytokine secretion and cytotoxic molecule expression) and they were not reactive to a pool of EBV/CMV/Flu virus peptides. Taken together, the combined analysis of transcripts and proteins of the TCR Vβ repertoire led to the identification of different types of CD8+ T cell clone expansion or contraction in healthy individuals, a situation that appears more complex than previously described in aged individuals

Cross-Reactivity of Herpesvirus-Specific CD8 T Cell Lines Toward Allogeneic Class I MHC Molecules

Although association between persistent viral infection and allograft rejection is well characterized, few examples of T-cell cross-reactivity between self-MHC/viral and allogeneic HLA molecules have been documented so far. We appraised in this study the alloreactivity of CD8 T cell lines specific for immunodominant epitopes from human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV). CD8 T cell lines were generated after sorting with immunomagnetic beads coated with either pp65495–503/A*0201, BMLF1259–267/A*0201, or BZLF154–64/B*3501 multimeric complexes. Alloreactivity of the CD8 T cell lines against allogeneic class I MHC alleles was assessed by screening of (i) TNF-α production against COS-7 cells transfected with as many as 39 individual HLA class I-encoding cDNA, and (ii) cytotoxicity activity toward a large panel of HLA-typed EBV-transformed B lymphoblastoid cell lines. We identified several cross-reactive pp65/A*0201-specific T cell lines toward allogeneic HLA-A*3001, A*3101, or A*3201. Moreover, we described here cross-recognition of HLA-Cw*0602 by BZLF1/B*3501-specific T cells. It is noteworthy that these alloreactive CD8 T cell lines showed efficient recognition of endothelial cells expressing the relevant HLA class I allele, with high level TNF-α production and cytotoxicity activity. Taken together, our data support the notion that herpes virus-specific T cells recognizing allo-HLA alleles may promote solid organ rejection

Magnétisme et matériaux magnétiques : introduction

This paper reviews a few main aspects of the solid state magnetism necessary to understand magnetic properties and behaviour of magnetic materials. The treatment of a subject as broad as present one must necessarily be limited and incomplete. Netherless we deal with the role of magnetism and magnetic materials in modern technology and cover some aspects of material such as : magnetostrictive and magnetoresistive materials, soft and hard magnetic materials, magnetic multilayers and magnetic recording

INFLUENCE OF THE DISLOCATION STRUCTURES ON THE BEHAVIOUR OF MAGNETIC DOMAIN WALLS IN HIGH PURITY IRON

The influence of dislocation density and arrangement on the movement of 90° magnetic domain walls (DW) was investigated by magnetomechanical damping measurements on high purity polycristalline iron. The dislocation structures created by straining at 300 K, 190 K and by straining at 77 K after prestraining at 300 K were observed by high voltage (800 KV) transmission electron microscopy (TEM). For the straining at 300 K, the effective internal stress σi and the reciprocal of the maximum magnetomechanical damping 1/QM-1 exhibit three linear stages, related to different dislocation distributions. The dislocation structures built by straining at 190 K and 77 K influence differently σi and 1/QM-1. This is linked to the more homogeneous distribution of dislocations created at low temperatures in iron

DÉTERMINATION PAR AMORTISSEMENT MAGNÉTOMÉCANIQUE DE LA RÉPARTITION DES CONTRAINTES INTERNES DANS LE FER PUR ÉCROUI

L'amortissement magnétomécanique dû aux déplacements irréversibles des parois de Bloch à 90° a été étudié dans le fer polycristallin de haute pureté en fonction de différentes structures de dislocations créées par écrouissages de traction à 300 K et à 190 K. Nous avons comparé les distributions de contraintes internes locales et les pertes magnétomécaniques au maximum d'amortissement pour tester la cohérence du modèle de Smith et Birchak, déjà utilisé pour décrire nos résultats expérimentaux. Il apparaît que seuls les arrangements de dislocations créés dans le stade II d'écrouissage à 300 K vérifient quantitativement le modèle. Dans le cas de distributions très hétérogènes (dislocations isolées et joints de grains en interaction avec les parois) il ne peut s'appliquer sans modifications tenant compte effectivement de l'arrangement des défauts.The magnetomechanical damping induced by the irreversible movements of 90° magnetic domain walls is studied on polycrystalline pure iron as a function of different dislocations structures built by tensile strainings at 300 K and 190 K. The distributions of internal local stresses and the magnetomechanical losses at the maximum of magnetomechanical damping have been compared to test the self consistency of the model of Smith and Birchak, already used to describe our experimental results. The only arrangements of dislocations created in the stage II by straining at 300 K are in quantitative agreement with the model. For non homogeneous distributions (isolated dislocations and grain boundaries interacting with magnetic walls) it cannot apply without modifications taking into account effectively the arrangement of defects

Microstructure Inspection by Means of Mechanical Barchausen Effect Analysis

This paper presents results of the application of the mechanical Barkhausen effect (MBE) for the evaluation of the strain dependence of magnetomechanical internal friction (MIF) and the internal stress distribution function. Both functions were obtained from the "first load" mechanical Barkhausen effect (MBE) strain dependence. The MBE intensity was measured with torque motor applying shear stress with constant time rate. This new method was tested for pure iron and Fe-C (160 ppm of C) alloy with different precipitation states. The evaluated strain dependence of the MIF was compared with the experimental MIF functions measured with a pendulum. It is sugested that the very close relationship between the two dependencies confirms the validity of the performed evaluation of the internal stress distribution function

INTRODUCTION TO THE STUDY OF DAMPING EFFECTS DUE TO MAGNETIC, ELECTRONIC PROPERTIES AND TO PHONONS INTERACTIONS

This introduction to theme V will be devided into two parts. The first part will be devoted to magnetic damping (7 papers) ; in the second part the interest will be focussed on electronic properties and phonons interactions (7 papers)

BEHAVIOUR OF MAGNETIC DOMAIN WALLS IN PRESENCE OF STRUCTURAL DEFECTS IN HIGH PURITY IRON

A partir de la mesure du frottement intérieur magnétomécanique, on a étudié l'influence de différents défauts structuraux (dislocations, joints de grains, interstitiels de carbone et carbures précipités) sur le comportement des parois de Bloch à 90° dans le fer pur. On détermine la distribution de contraintes internes locales et le facteur de forme du cycle d'hystérésis magnétomécanique, définis dans le modèle de Smith et Birchak [1]. Leurs variations sont reliées aux modifications de densité et d'arrangement des défauts de structure étudiés.Using magnetomechanical damping experiments, we have studied the influence of various structural defects (dislocations, grain boundaries, interstitial carbon atoms and precipitated carbides) on the hysteretic behaviour of 90° magnetic domain walls (DW's) in pure iron. The distribution of internal local stresses and the shape factor of the magnetomechanical hysteresis cycle, as defined in the model of Smith and Birchak [1], have been examined. Their variations are linked to the modifications of density and arrangement of structural defects

Propriétés magnétiques d'alliages Fe-6,5%Si élaborés par solidification rapide sous atmosphère contrôlée. Comparaison avec des alliages Fe-3,2%Si industriels

Les caractéristiques magnétiques de rubans de Fe-6,5%Si élaborés par solidification rapide sous atmosphère contrôlée ont été comparées à celles d'alliages industriels à grains orientés et non orientés. Dès 150 Hz, l'évolution des caractéristiques des rubans est plus favorable.The magnetic properties of Fe-6,5%Si ribbons obtained by a rapid quenching in a controlled atmosphere have been compared with those of grain oriented and non oriented industrial alloys. For frequencies higher than 150 Hz these properties turn out to be better than those of industrial alloys