Critical role for the chemokine receptor CXCR6 in NK cell-mediated antigen-specific memory of haptens and viruses.

Hepatic natural killer (NK) cells mediate antigen-specific contact hypersensitivity (CHS) in mice deficient in T cells and B cells. We report here that hepatic NK cells, but not splenic or naive NK cells, also developed specific memory of vaccines containing antigens from influenza, vesicular stomatitis virus (VSV) or human immunodeficiency virus type 1 (HIV-1). Adoptive transfer of virus-sensitized NK cells into naive recipient mice enhanced the survival of the mice after lethal challenge with the sensitizing virus but not after lethal challenge with a different virus. NK cell memory of haptens and viruses depended on CXCR6, a chemokine receptor on hepatic NK cells that was required for the persistence of memory NK cells but not for antigen recognition. Thus, hepatic NK cells can develop adaptive immunity to structurally diverse antigens, an activity that requires NK cell-expressed CXCR6.

Role of the naive and memory CD4+T-cell repertoire in transplantation

Purpose: The exact role of individual T cell-subsets in the development of rejection is not clearly defined. Given their distinct phenotypes, effector functions and trafficking patterns, naïve (CD45RBhiCD44lo) and memory (CD45RBloCD44hi) T cells may play distinct roles in anti-donor immunity after transplantation. Furthermore, only the CD4+CD45RBlo population contains CD4+CD25+ T cells, a subset with suppressive functions playing a major role in the maintenance of peripheral tolerance. The aim of this work was to study the contribution of these individual subsets in alloresponses via the direct and indirect pathways using a murine experimental model. Methods and materials: Purified naïve or memory CD4+ T cells were adoptively transferred into lymphopenic mice undergoing a skin allograft. Donor to recipient MHC combinations were chosen in order to study the direct and the indirect pathways of allorecognition separately. Graft survival and in vivo expansion, effector function and trafficking of the transferred T cells was assessed at different time points after transplantation. Results: We found that the cross-reactive CD4+CD45RBlo memory T-cell pool was heterogeneous and contained cells with regulatory potentials, both in the CD4+CD25+ and CD4+CD25-populations. CD4+ T cells capable of inducing strong primary alloreactive responses in vitro and rejection of a first allograft in vivo were mainly contained within the CD45RBhi naïve CD4+ T-cell compartment. CD4+CD45RBlo T cells proliferated less abundantly to allogeneic stimulation than their naïve counterparts both in vitro and in vivo, and allowed prolonged allograft survival even after the depletion of the CD4+CD25+ subset. Interestingly, CD4+CD25-CD45RBlo T cells were capable of prolonging allograft survival, mainly when the indirect pathway was the only mechanism of allorecognition. The indirect pathway response, which was shown to drive true chronic rejection and contribute to chronic allograft dysfunction, was predominantly mediated by naïve CD4+ T cells. Conclusion: This work provides new insights into the mechanisms that drive allograft rejection and should help develop new clinical immunosuppressive protocols. In particular, our results highlight the importance of selectively targeting individual T-cell subsets to prevent graft rejection but at the same time maintain immune protective responses to common pathogens.

Distinct profiles of cytotoxic granules in memory CD8 T cells correlate with functions, differentiation stage, and antigen exposure

RAPPORT DE SYNTHÈSE : Les profils des granules cytotoxiques des cellules T CD8 mémoires sont corrélés à la fonction, à leur état de différentiation et à l'exposition à l'antigène. Les lymphocytes T-CD8 cytotoxiques exercent leur fonction antivirale et antitumorale surtout par la sécrétion des granules cytotoxiques. En général, ce sont l'activité de dégranulation et les granules cytotoxiques (contenant perforine et différentes granzymes) qui définissent les lymphocytes T-CD8 cytotoxiques. Dans cette étude, nous avons investigué l'expression de granzyme K par cytométrie en flux, en comparaison avec l'expression de granzyme A, granzyme B et de perforine. L'expression des granules cytotoxiques a été déterminée dans lymphocytes T-CD8 qui étaient spécifiques pour des différents virus, en particulier spécifique pour le virus d'influenza (flu), le virus Ebstein Barr (EBV), le virus de cytomégalie (CMV) et le virus de l'immunodéficience humaine (HIV). Nous avons observé une dichotomie entre l'expression du granzyme K et de la perforine dans les lymphocytes T-CD8 qui étaient spécifiques aux virus mentionnés. Les profils des lymphocytes T-CD8 spécifiques à flu étaient positifs soit pour granzyme A et granzyme K soit pour le granzyme K seul, mais dans l'ensemble négatifs pour perforine et granzyme B. Les cellules spécifiques à CMV étaient dans la plupart positives pour perforine, granzyme B et A, mais négatives pour le granzyme K. Les cellules spécifiques à EBV et HIV étaient dans la majorité positives pour granzyme A, B et K, et dans la moitié des cas négatives pour la perforine. Nous avons également analysé, selon les marqueurs de mémoire de CD45 et CD127, les profils de différentiation cellulaire: Les cellules avec les granules cytotoxiques contenant exclusivement le granzyme K, étaient associées à un état de différentiation précoce. Au contraire, les protéines cytolytiques perforine, granzyme A et B, correspondent à une différentiation avancée. En outre, les protéines perforine et granzyme B, mais pas les granzymes A et K, sont corrélées à une activité cytotoxique. Finalement, des changements dans l'exposition d'antigène in vitro et in vivo suivant une infection primaire d' HIV ou une vaccination modulent le profil de granules cytotoxiques. Ces résultats nous permettent d'étendre la compréhension de la relation entre les différents profils de granules cytotoxiques des lymphocytes T-CD8 et leur fonction, leur état de différentiation et l'exposition à l'antigène.

Human CD8 T-cell responses to Epstein-Barr virus and Cytomegalovirus in healthy donors and melanoma patients

Summary The mechanisms regulating the protective immune T-cell responses generated against the persistent Epstein-Barr virus (EBV) and Cytomegaloviru_s (CNIV) remain poorly understood. We analyzed the dynamics of cellular differentiation and T-cell receptor (TCR) clonotype selection of EBV- and CMV-specific T-cells in healthy adults and melanoma patients. While these responses could be subdivided into four T lymphocyte populations, théir proportions varied between EBV and CMV specific responses. Phenotypic and TCR clonotypic analyses supported a linear model of differentiation from the early-differentiated (EM/CD28pos) subset to the late-differentiatdc (EMRA/CD28neg) subset. In-depth clonal composition analyses revealed TCR repertoires, which were highly restricted for CMV- and relatively diverse for EBV-specific cells. Virtually all virus-specific clonotypes identified in the EMRA/CD28neg subset were also found within the pool of less differentiated "memory" cells. However, striking differences in the patterns of dominance were observed among these subsets, as some clonotypes were selected with differentiation, while others were not. Latedifferentiated CMV-specific clonotypes were mostly characterized by TCRs with lower dependency on CD8 co-receptor interaction. Yet all clonotypes displayed similar functional avidities, suggesting a compensatory role of CD8 in the clonotypes of lower TCR avidity. Importantly, clonotype selection and composition of each virus-specific subset upon differentiation was highly preserved over time, with the presence of the same dominant clonotypes at specific differentiation stages within a period of four years. This work was extended to the study of EBV-specific CD8 T-cell responses in melanoma patients undergoing transient lymphodepletion, followed by adoptive cell transfer (ACT) and immune reconstitution for thè treatment of their tumors. Following treatment regimen, we first observed an increase in the proportion of virus-specific T-cells in 3 out of 5 patients, accompanied by a more differentiated phenotype (EMRA/CD28neg), compared to specific cells of healthy individuals. Yet, similarly to healthy donors, clonotype selection and composition of virus-specific T-cells varied along the pathway of cellular differentiation, with some clonotypes being selected with differentiation, while others were not. Intriguingly, no novel clonotypes emerged following transient immuno-suppression and homeostatic proliferation, finding which was subsequently explained by the absence of EBV reactivation. The distribution of each clonotype within early- and late-differentiated T-cell subsets in 4 out 5 patients was highly stable over time, with those clonotypes initially found before the start of treatment that were again present at specific differentiation stages after transient lymphodepletion and ACT. These findings uncover novel features of the highly sophisticated control of steady state protective T-cell immune responses against persistent herpesviruses in healthy adults. Furthermore they reveal the striking stability of these responses in terms of clonotype selection and composition with T-cell differentiation even in situations where the immune system has been. challenged. Résumé : Les mécanismes qui régulent les réponses immunitaires de type protectrices, générées contre les virus chroniquement persistants tels que l'Epstein-Barr (EBV) ou le Cytomegalo (CMV) restent largement inconnus. Nous avons analysé la différenciation des lymphocytes T spécifiques pour ces virus, ainsi que la composition des clonotypes T (par leur récepteur T) chez les donneurs sains. Les réponses immunes peuvent être classifiées en quatre souspopulations majeures de lymphocytes T, cependant, leur proportion varie entre les réponses spécifiques contre EBV ou CMV. Ces analyses soutiennent le modèle linéaire de différenciation, à partir de la population non différenciée (EM/CD28pos) vers la population plus différenciée (ENIIZA/CD28neg). De plus, nos données sur la composition clonale de ces cellules T spécifiques ont révélé des répertoires TCR restreints, pour la réponse anti-CMV, et relativement diversifiés contre EBV. Tous les clonotypes spécifiques de ces virus identifiés dans la sous-population différenciée EMRA/CD28neg, ont également été retrouvés dans la population de cellules "mémoires". Toutefois, de fortes différences ont été observées dans les schémas de domination de ces sous-populations, en effet, certains clonotypes étaient sélectionnés avec la différenciation, alors que d'autres ne l'étaient pas. Nous avons également démontré que ces clonotypes différenciés et spécifiques pour le CMV sont caractérisés par des TCRs à faible dépendance en regard de la coopération du corécepteur CD8. Néanmoins, tous les clonotypes affichent une avidité fonctionnelle similaire, suggérant un rôle compensatoire du CD8, dans le cas des clonotypes avec une faible avidité du TCR En définitive, la composition et la sélection des clonotypes spécifiques pour chaque virus et pour chaque sous-population suit un schéma de différenciation hautement conservé au cours du temps, avec la présence de ces mêmes clonotypes au même stade de différenciation sur une période de quatre ans. Ce travail a été étendu à l'étude des réponses T CD8+ spécifiques pour le virus EBV chez les patients atteints de mélanome et recevant dans le cadre du traitement de leurs tumeurs une lymphodéplétion transitoire, suivie d'un transfert adoptif de cellules et d'une reconstitution immunitaire. Au cours de cette thérapie, nous avons en premier lieu observé pour 3 des 5 patients une augmentation de la proportion de cellules T spécifiques pour le virus, accompagné d'un phénotype plus différencié (EMRA/CD28neg), et ceci comparativement à des cellules spécifiques d'individus sains. Pourtant, comme nous l'avons observé chez les donneurs sains, la sélection et la composition des clonotypes T spécifiques varient tout au long de la différenciation cellulaire, avec certains clonotypes sélectionnés et d'autres qui ne le sont pas. Étonnamment, aucun nouveau clonotype n'a émergé après l'immuno-suppression transitoire et la prolifération homéostatique. Cette observation trouve son explication par une absence de réactivation du virus EBV chez ces patients, et ce malgré leur traitement. De plus, la distribution de chaque clonotype parmi ces sous-populations non-différenciées et différenciées reste stable au cours du traitement. Ainsi, les mêmes clonotypes initialement identifiés avant le début du traitement sont présents aux mêmes stades de différenciation après la lymphodéplétion et la prolifération homéostatique. Ces résultats ont permis d'identifier de nouveaux mécanismes impliqués dans la régulation hautement «sophistiquée » des réponses immunitaires T contre les virus persistants EBV et CMV chez les donneurs sains. En particulier, ils révèlent la grande stabilité de ces réponses en termes de sélection et de composition des clonotypes avec la différenciation cellulaire, et ce dans les situations chroniques, ainsi que dans les situations dans lesquelles le système immunitaire a été profondément perturbé.

Telomere fluorescence measurements in granulocytes and T lymphocyte subsets point to a high turnover of hematopoietic stem cells and memory T cells in early childhood.

To study telomere length dynamics in hematopoietic cells with age, we analyzed the average length of telomere repeat sequences in diverse populations of nucleated blood cells. More than 500 individuals ranging in age from 0 to 90 yr, including 36 pairs of monozygous and dizygotic twins, were analyzed using quantitative fluorescence in situ hybridization and flow cytometry. Granulocytes and naive T cells showed a parallel biphasic decline in telomere length with age that most likely reflected accumulated cell divisions in the common precursors of both cell types: hematopoietic stem cells. Telomere loss was very rapid in the first year, and continued for more than eight decades at a 30-fold lower rate. Memory T cells also showed an initial rapid decline in telomere length with age. However, in contrast to naive T cells, this decline continued for several years, and in older individuals lymphocytes typically had shorter telomeres than did granulocytes. Our findings point to a dramatic decline in stem cell turnover in early childhood and support the notion that cell divisions in hematopoietic stem cells and T cells result in loss of telomeric DNA.

Ferromagnetic shape memory alloys: structural and thermal properties

The most extensively studied Heusler alloys are those based on the Ni-Mn-Ga system. However, to overcome the high cost of Gallium and the usually low martensitic transformation temperature, the search for Ga-free alloys has been recently attempted, particularly, by introducing In, Sn or Sb. In this work, two alloys (Mn50Ni35.5In14.5 and Ni50Mn35In15) have been obtained by melt spinning. We outline their structural and thermal behaviour. Mn50Ni35.5In14.5 alloy has the transformation above room temperature whereas Ni50Mn35In15 does not have this transformation in the temperature range here analyzed

Working memory in schizophrenia: dynamic visuo-spatial information processing

Working memory, commonly defined as the ability to hold mental representations on line transiently and to manipulate these representations, is known to be a core deficit in schizophrenia. The aim of the present study was to investigate the visuo-spatial component of the working memory in schizophrenia, and more precisely to what extent the dynamic visuo-spatial information processing is impaired in schizophrenia patients. For this purpose we used a computerized paradigm in which 29 patients with schizophrenia (DSMIV, Diagnostic Interview for Genetic Studies) and 29 age and sex matched control subjects (DIGS) had to memorize a plane moving across the computer screen and to identify the observed trajectory among 9 plots proposed together. Each trajectory could be seen max. 3 times if needed. The results showed no difference between schizophrenia patients and controls regarding the number of correct trajectory identified after the first presentation. However, when we determine the mean number of correct trajectories on the basis of 3 trials, we observed that schizophrenia patients are significantly less performant than controls (Mann-Whitney, p _ 0.002). These findings suggest that, although schizophrenia patients are able to memorize some dynamic trajectories as well as controls, they do not profit from the repetition of the trajectory presentation. These findings are congruent with the hypothesis that schizophrenia could induce an unbalance between local and global information processing: the patients may be able to focus on details of the trajectory which could allow them to find the right target (bottom-up processes), but may show difficulty to refer to previous experience in order to filter incoming information (top-down processes) and enhance their visuo-spatial working memory abilities.

Muistitietotutkijat koolla Sydneyssä : Dancing with memory : oral history and its audiences

Ajankohtaista

Monitieteistä muistitietotutkimusta : Memory and narration

Ajankohtaista

Postnatal intracerebroventricular administrations of NGF alter spatial memory in adulthood

The present work assessed the effects of intracerebroventricular injections (2x5 mg/2.5 ml) of recombined human nerve growth factor (rhNGF) at postnatal days 2 and 3 upon the development of spatial learning capacities in rats. The treated rats were trained at the age of 22 days to escape onto an invisible platform at a fixed position in space in a Morris navigation task. For half of the subjects, the training position was also cued, a procedure aimed at facilitating escape and reducing attention to the distant spatial cues. At the age of 2 months all the rats were retrained in the same task. Treatment effects were found in both immature and adult rats. The injection of NGF induced a slight alteration of the immature rats' performance. In contrast, a marked impairment of spatial abilities was shown in the 2-month-old rats. The most consistent effects were a significant increase in the escape latency and a decrease bias towards the training platform area during probe trials. The reduction of spatial memory was particularly marked if the subjects had been trained in a cued condition. Taken together, these experiments reveal that an acute pharmacological treatment that leads to transient modifications during early development might induce a behavioural change long after treatment. Thus, the development and the maintenance of an accurate spatial representation are tightly related to the development of brain structures that could be altered by precocious NGF administrations.

Cerebellar lesions: is there a lateralisation effect on memory deficits?

BACKGROUND: Until recently, neurosurgeons eagerly removed cerebellar lesions without consideration of future cognitive impairment that might be caused by the resection. In children, transient cerebellar mutism after resection has lead to a diminished use of midline approaches and vermis transection, as well as reduced retraction of the cerebellar hemispheres. The role of the cerebellum in higher cognitive functions beyond coordination and motor control has recently attracted significant interest in the scientific community, and might change the neurosurgical approach to these lesions. The aim of this study was to investigate the specific effects of cerebellar lesions on memory, and to assess a possible lateralisation effect. METHODS: We studied 16 patients diagnosed with a cerebellar lesion, from January 1997 to April 2005, in the "Centre Hospitalier Universitaire Vaudois (CHUV)", Lausanne, Switzerland. Different neuropsychological tests assessing short term and anterograde memory, verbal and visuo-spatial modalities were performed pre-operatively. RESULTS: Severe memory deficits in at least one modality were identified in a majority (81%) of patients with cerebellar lesions. Only 1 patient (6%) had no memory deficit. In our series lateralisation of the lesion did not lead to a significant difference in verbal or visuo-spatial memory deficits. FINDINGS: These findings are consistent with findings in the literature concerning memory deficits in isolated cerebellar lesions. These can be explained by anatomical pathways. However, the cross-lateralisation theory cannot be demonstrated in our series. The high percentage of patients with a cerebellar lesion who demonstrate memory deficits should lead us to assess memory in all patients with cerebellar lesions.

Visuospatial working memory deficits and visual pursuit impairments are not directly related in schizophrenia.

OBJECTIVE: Patients with schizophrenia show deficits in visuospatial working memory and visual pursuit processes. It is currently unclear, however, whether both impairments are related to a common neuropathological origin. The purpose of the present study was therefore to examine the possible relations between the encoding and the discrimination of dynamic visuospatial stimuli in schizophrenia. METHOD: Sixteen outpatients with schizophrenia and 16 control subjects were asked to encode complex disc displacements presented on a screen. After a delay, participants had to identify the previously presented disc trajectory from a choice of six static linear paths, among which were five incorrect paths. The precision of visual pursuit eye movements during the initial presentation of the dynamic stimulus was assessed. The fixations and scanning time in definite regions of the six paths presented during the discrimination phase were investigated. RESULTS: In comparison with controls, patients showed poorer task performance, reduced pursuit accuracy during incorrect trials and less time scanning the correct stimulus or the incorrect paths approximating its global structure. Patients also spent less time scanning the leftmost portion of the correct path even when making a correct choice. The accuracy of visual pursuit and head movements, however, was not correlated with task performance. CONCLUSIONS: The present study provides direct support for the hypothesis that active integration of visuospatial information within working memory is deficient in schizophrenia. In contrast, a general impairment of oculomotor mechanisms involved in smooth pursuit did not appear to be directly related to lower visuospatial working memory performance in schizophrenia.

A Candidate HIV/AIDS Vaccine (MVA-B) that Enhances the Magnitude and Polyfunctionality of Memory HIV-1-Specific T-Cell Responses

Background: The poxvirus vector Modified Vaccinia Virus Ankara (MVA) expressing HIV-1 Env, Gag, Pol and Nef antigens from clade B (MVA-B) is currently used as a HIV/AIDS vaccine candidate. A general strategy to try to improve the immunogenicity of poxvirus HIV-1 vaccine candidates is the deletion of known or suggested immunomodulatory vaccinia virus (VACV) genes.Methods: We have generated and characterized the innate immune sensing and the immunogenicity profile of a new HIV-1 vaccine candidate, which contains a deletion in a VACV gene.Results: We show that this VACV protein is expressed early during virus infection and localizes to the cytoplasm of infected cells. Deletion of this VACV gene from the MVA-B had no effect on virus growth kinetics; therefore this VACV protein is not essential for virus replication. The innate immune signals elicited by the MVA-B deletion mutant in human macrophages and monocyte-derived dendritic cells were characterized. In a DNA prime/MVA boost immunization protocol in mice, flow cytometry analysis revealed that the MVA-B deletion mutant enhanced the magnitude and polyfunctionality of the HIV-1-specific CD4 + and CD8 + T-cell memory immune responses, with most of the HIV-1 responses mediated by the CD8 + T-cell compartment with an effector phenotype. Significantly, while MVA-B induced preferentially Env- and Gag-specific CD8 + T-cell responses, the MVA-B deletion mutant induced more GPN-specific CD8 + T-cell responses. Furthermore, the MVA-B deletion mutant enhanced the levels of antibodies against Env in comparison with MVA-B.Conclusion: These findings revealed that this new VACV protein can be considered as an immunomodulator and that deleting this gene in MVA-B confers an immunological benefit by inducing innate immune responses and increasing the magnitude and quality of the T-cell memory immune responses to HIV-1 antigens. Our observations are relevant for the improvement of MVA vectors as HIV-1 vaccines.

Auditory stimulation does not induce implicit memory during anaesthesia

Background and aim of the study: Formation of implicit memory during general anaesthesia is still debated. Perceptual learning is the ability to learn to perceive. In this study, an auditory perceptual learning paradigm, using frequency discrimination, was performed to investigate the implicit memory. It was hypothesized that auditory stimulation would successfully induce perceptual learning. Thus, initial thresholds of the frequency discrimination postoperative task should be lower for the stimulated group (group S) compared to the control group (group C). Material and method: Eighty-seven patients ASA I-III undergoing visceral and orthopaedic surgery during general anaesthesia lasting more than 60 minutes were recruited. The anaesthesia procedure was standardized (BISR monitoring included). Group S received auditory stimulation (2000 pure tones applied for 45 minutes) during the surgery. Twenty-four hours after the operation, both groups performed ten blocks of the frequency discrimination task. Mean of the thresholds for the first three blocks (T1) were compared between groups. Results: Mean age and BIS value of group S and group C are respectively 40 } 11 vs 42 } 11 years (p = 0,49) and 42 } 6 vs 41 } 8 (p = 0.87). T1 is respectively 31 } 33 vs 28 } 34 (p = 0.72) in group S and C. Conclusion: In our study, no implicit memory during general anaesthesia was demonstrated. This may be explained by a modulation of the auditory evoked potentials caused by the anaesthesia, or by an insufficient longer time of repetitive stimulation to induce perceptual learning.