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PubMed1992

Differential effect of interleukin 1 on naive and memory CD4+ T cells.

Freshly derived murine CD4+ T cells are divided into naive and memory cells based on the expression of CD45 isoforms. Cross-linking the T cell receptor CD3 complex either by plastic-bound anti-CD3 antibodies or the antibody presented on non-lymphoid Fc gamma receptor type II-positive Chinese hamster ovary cells in absence of competent antigen-presenting cells fails to activate naive cells to either secrete cytokines or to proliferate. In contrast, memory cells secrete their characteristic cytokines [interleukin (IL) 2, IL4, and interferon-gamma] and show significant proliferation to this stimulus. IL 1 however, is required for their optimal clonal expansion. Differential expression of IL 1 receptor mRNA in memory cells also correlate with their responsiveness to IL 1. Thus, these data reveal a basic difference in the requirements for activation of naive and memory CD4+ T cells.

Animals↗
PubMed1997

Nonverbal memory assessment with designs: construct validity and clinical utility.

The evaluation of memory is often a principal objective in psychological testing, especially for older adults. Differentiation between subtypes of memory functioning is critical in making differential diagnoses and in predicting everyday functioning. In this paper, 23 tests using memory for designs and developed for clinical or research applications are reviewed. Overall, reliabilities are low, normative samples varied in size, and findings regarding the construct validity of design memory testing are mixed. Tests with higher reliability, large numbers of designs, and recognition formats may be more specific to nonverbal memory. A series of studies that systematically establishes construct validity for design memory tests will enhance clinical utility.

Adult↗
PubMed2005

Characterization of subsets of CD4+ memory T cells reveals early branched pathways of T cell differentiation in humans.

The pathways for differentiation of human CD4(+) T cells into functionally distinct subsets of memory cells in vivo are unknown. The identification of these subsets and pathways has clear implications for the design of vaccines and immune-targeted therapies. Here, we show that populations of apparently naive CD4(+) T cells express the chemokine receptors CXCR3 or CCR4 and demonstrate patterns of gene expression and functional responses characteristic of memory cells. The proliferation history and T cell receptor repertoire of these chemokine-receptor(+) cells suggest that they are very early memory CD4(+) T cells that have "rested down" before acquiring the phenotypes described for "central" or "effector" memory T cells. In addition, the chemokine-receptor(+) "naive" populations contain Th1 and Th2 cells, respectively, demonstrating that Th1/Th2 differentiation can occur very early in vivo in the absence of markers conventionally associated with memory cells. We localized ligands for CXCR3 and CCR4 to separate foci in T cell zones of tonsil, suggesting that the chemokine-receptor(+) subsets may be recruited and contribute to segregated, polarized microenvironments within lymphoid organs. Importantly, our data suggest that CD4(+) T cells do not differentiate according to a simple schema from naive --> CD45RO(+) noneffector/central memory --> effector/effector memory cells. Rather, developmental pathways branch early on to yield effector/memory populations that are highly heterogeneous and multifunctional and have the potential to become stable resting cells.

CD4-Positive T-Lymphocytes↗
PubMed1987

Abnormal temporal lobe response in Alzheimer's disease during cognitive processing as measured by 11C-2-deoxy-D-glucose and PET.

Elderly controls and probable Alzheimer's disease patients underwent serial positron emission tomography (PET) studies during a baseline condition and while performing a verbal memory task. For the temporal lobes, all 7 Alzheimer patients demonstrated a relative shift in glucose metabolic rates to the right hemisphere during the memory condition relative to baseline, and 5 of 7 controls showed a shift to the left hemisphere. Baseline absolute regional metabolic rates replicate previous findings and were somewhat less useful than the memory challenge in differentiating patients from controls. These results indicate that a temporal lobe abnormality in Alzheimer's disease is related to memory performance.

Aged↗
PubMed2002

Chromatin remodeling in nuclear cloning.

Nuclear cloning is a procedure to create new animals by injecting somatic nuclei into unfertilized oocytes. Recent successes in mammalian cloning with differentiated adult nuclei strongly indicate that oocyte cytoplasm contains unidentified remarkable reprogramming activities with the capacity to erase the previous memory of cell differentiation. At the heart of this nuclear reprogramming lies chromatin remodeling as chromatin structure and function define cell differentiation through regulation of the transcriptional activities of the cells. Studies involving the modification of chromatin elements such as selective uptake or release of binding proteins, covalent histone modifications including acetylation and methylation, and DNA methylation should provide significant insight into the molecular mechanisms of nuclear dedifferentiation and redifferentiation in oocyte cytoplasm.

Acetylation↗
PubMed1996

The effect on memory of chronic prednisone treatment in patients with systemic disease.

There have been no systematic investigations of the effects of glucocorticoid treatment on memory in a clinical population despite experimental and clinical evidence that such treatment could cause memory disturbance. We conducted both cross-sectional and longitudinal studies. In Study 1, we administered tests of both hippocampal-dependent explicit memory and hippocampal-independent implicit memory to twenty-five prednisone-treated patients with systemic disease without CNS involvement and 25 matched clinical controls. All treated patients were taking doses of 5 to 40 mg of prednisone daily for at least 1 year. The glucocorticoid-treated group performed worse than the controls on tests of explicit memory, but the groups did not differ on the implicit memory task. Multiple regression analyses suggested that elderly patients are more susceptible to memory impairment with less protracted treatment. The results of Study 2, a prospective, longitudinal study of the effects of prednisone on memory across 3 months of therapy, suggest that even acute treatment can adversely affect memory. The observed alteration in memory was not secondary to inattention, affective disturbance, generalized global cognitive decline, or severity of disease. Results reported here, combined with previous clinical and experimental reports, indicate that the risk of memory impairment should be carefully considered before initiating treatment with glucocorticoids. Conversely, use of glucocorticoids should be considered in the differential diagnosis of memory loss. Finally, the potential benefit of anti-inflammatory treatment in Alzheimer's disease might be counterbalanced by possible iatrogenic memory impairment, at least when synthetic glucocorticoids are considered.

Adult↗
PubMed1997

A comparison of semantic memory in vascular dementia and dementia of Alzheimer's type.

OBJECTIVE: To determine whether semantic memory is impaired in vascular dementia and to assess the utility of semantic memory measures in differentiating vascular dementia from dementia of Alzheimer's type (DAT). DESIGN: Case-control study. PATIENTS: Ten patients with Cambridge Mental Disorders in the Elderly (CAMDEX) diagnosis of 'definite' mild or moderate vascular dementia (mean age 77) were individually matched with 10 patients with a CAMDEX diagnosis of 'definite' DAT on the basis of age, education, sex, premorbid IQ (as measured by the National Adult Reading Test) and performance on the Cambridge Cognitive Examination (CAMCOG). In addition, 10 age, sex and education matched volunteer or relative controls were assessed. OUTCOME MEASURES: A detailed semantic memory test battery consisting of five subtests: category fluency, picture naming, picture sorting, word-picture matching and generation of verbal definitions. RESULTS: Compared to normal controls, both patient groups were impaired on all subtests of the semantic battery with the exception of the word-picture matching test. No differences were found between the vascular dementia and DAT groups on any of the measures. CONCLUSIONS: Impairment of semantic memory is a feature of both vascular dementia and DAT. Tests of semantic memory appear, therefore, of little value in differentiating between these two major causes of dementia. Further work is required to determine whether the nature of the processing deficit is the same in these conditions.

Aged↗
PubMed1995

Real-time compression of myoelectric data utilising adaptive differential pulse code modulation.

The myoelectric signal, obtained by either surface or needle electrodes, is used in many areas of clinical research and diagnosis. The conventional method of storing such information is in digitised form on a computer. However, the bandwidth of the signal and the required resolution result in large memory requirements. Adaptive differential pulse code modulation is investigated as a method of reducing the memory requirements for myoelectric data storage. In this scheme, a 12-bit sample is reduced to four bits, thus reducing the memory requirements by a factor of three. In reality, this compression ratio is closer to 4:1 owing to the fact that the widths of most memories are organised as multiples of eight bits.

Computer Systems↗
PubMed2005

Differential induction of c-Jun and Fos-like proteins in rat hippocampus and dorsal striatum after training in two water maze tasks.

Research examining the neuroanatomical bases of memory in mammals suggests that the hippocampus and dorsal striatum are parts of independent memory systems that mediate "cognitive" and stimulus-response "habit" memory, respectively. At the molecular level, increasing evidence indicates a role for immediate early gene (IEG) expression in memory formation. The present experiment examined whether acquisition of cognitive and habit memory result in differential patterns of IEG protein product expression in these two brain structures. Adult male Long-Evans rats were trained in either a hippocampal-dependent spatial water maze task, or a dorsal striatal-dependent cued water maze task. Ninety minutes after task acquisition, brains were removed and processed for immunocytochemical procedures, and the number of cells expressing Fos-like immunoreactivity (Fos-like-IR) and c-Jun-IR in sections from the dorsal hippocampus and the dorsal striatum were counted. In the dorsal hippocampus of rats trained in the spatial task, there were significantly more c-Jun-IR pyramidal cells in the CA1 and CA3 regions, relative to rats that had acquired the cued task, yoked controls (free-swim), or naïve (home cage) rats. Relative to rats receiving cued task training and control conditions, increases in Fos-like IR were also observed in the CA1 region of rats trained in the spatial task. In rats that had acquired the cued task, patches of c-Jun-IR were observed in the posteroventral striatum; no such patches were evident in rats trained in the spatial task, yoked-control rats, or naïve rats. The results demonstrate that IEG protein product expression is up-regulated in a task-dependent and brain structure-specific manner shortly after acquisition of cognitive and habit memory tasks.

Animals↗
PubMed2004

CD4 T cells guarantee optimal competitive fitness of CD8 memory T cells.

We studied the contribution of CD4 T cell help to survival and competitive fitness of CD8 memory T cells specific for influenza virus nucleoprotein. In agreement with recent studies, the optimal generation of functional memory CD8 T cells required CD4 help, although long-term maintenance of resting CD8 memory T cells did not absolutely depend on the presence of CD4 T cells. Nonetheless, CD4 T cells were essential during differentiation of CD8 memory T cells to imprint on them the capacity to compete effectively with other memory T cells. CD8 memory cells generated with help survived better in secondary polyclonal hosts, and co-transfer into lymphopenic hosts together with "un-helped" CD8 memory cells showed improved homeostatic expansion of CD8 memory cells that had been generated with CD4 help. Therefore, the requirement for CD4 help in CD8 T cell memory extends to homeostatic parameters that ensure the maintenance and competitive fitness of memory clones.

Animals↗
PubMed2003

[Executive functions and prospective memory performance in old age: an analysis of event-based and time-based prospective memory].

The goal of the present study was to examine the role of executive functions in age-related differences in prospective memory. Therefore, in a sample of 40 young ( M=24.8; SD=2.0) and 40 old adults ( M=69.3; SD=5.6), event- and time-based prospective memory as well as five executive functions were assessed. Results show that age differences in prospective memory performance depend largely on age-related individual differences in executive functions. Furthermore, the results indicate several executive functions to differentially predict prospective memory performance. The event-based prospective memory task requires inhibition to avoid distraction from irrelevant items. The time-based prospective memory task requires the flexible shifting of cognitive sets. Overall, the data support the assumption that age differences in prospective memory performance are closely related to executive functioning. In addition, time- and event-based prospective memory seem to rely on different executive processes.

Adult↗
PubMed2003

CD7 is a differentiation marker that identifies multiple CD8 T cell effector subsets.

The adaptive immune response of human CD8 T cells to invading pathogens involves the differentiation of naive cells into memory and effector cells. However, the lineage relationship between memory and effector cells and the differentiation of CD8 T cells into distinct subsets of effector cell subpopulations are subjects of considerable debate. CD7 identifies three populations of CD8 T cells: CD7 high (CD7(high)), low (CD7(low)), and negative (CD7(neg)) that translate into subsets with distinct functional properties. The CD7(high) subset contains naive and memory cells and the CD7(low) and CD7(neg) subsets contain effector cells. The effector cells can functionally be divided into cytokine-secreting effector CD8 T cells and lytic effector CD8 T cells. These data provide a model of human CD8 T cell differentiation in which specialized distinct subpopulations can be identified by expression of CD7.

Antigens, CD7↗
PubMed1997

Memory, but not naive, peripheral blood B lymphocytes differentiate into Ig-secreting cells after CD40 ligation and costimulation with IL-4 and the differentiation factors IL-2, IL-10, and IL-3.

The ligation of CD40 on B lymphocytes by CD40 ligand, transiently expressed on activated Th cells, provides a key activation signal required for the germinal center B cell response. In vitro, human B cell activation has been investigated extensively by coculturing tonsillar B cells with CD32-transfected fibroblasts coated with anti-CD40 Abs, in the presence of cytokines (the CD40 system). When tonsillar IgD+ B cells are cultured in the CD40 system with IL-4, cells proliferate and switch to IgG, but they display a block of differentiation illustrated by the persistence of IgD expression on cycling B cells. In this study, we analyzed the responses of peripheral blood B lymphocyte fractions, which may contain fewer in vivo activated cells than those from tonsils. While the differentiation block was confirmed with peripheral naive B cells cultured in the CD40 system with IL-4, it was also observed with the combination of IL-2, IL-10, and IL-3 alone or together with IL-4 (persistence of >90% IgD+ cells, including 24-60% IgD+, IgG+ cells, and <6% IgD+, IgA+ cells after 8 days). IgD+, IgG-, and IgA- (naive) B cells secreted 70-fold less Ig than IgG+, IgA+ (memory) B cells in response to anti-CD40 plus IL-2, IL-10, and IL-3. IgG-, IgA- B cells, or IgD-, IgM+, which should include IgM+ memory cells, strongly secreted IgM, but no IgG. In conclusion, only memory B cells secreted Ig; like memory T cells, their activation requirements to differentiate into effector cells seem less stringent than those of the naive cells.

Antibody Formation↗
PubMed2000

Human vascular endothelial cells stimulate memory but not naive CD8+ T cells to differentiate into CTL retaining an early activation phenotype.

Endothelial cell (EC)-selective alloreactive CTL may mediate alloimmune vascular injury. In the present study, EC-selective CTL were generated in cocultures of purified human CD8+ T cells with allogeneic EC and were compared with conventional CTL against corresponding B lymphoblastoid cells (BLC). EC caused activation and expansion of memory but not naive CD8+ T cells, which differentiated into EC-selective CTL that retained high surface expression of CD69, CD25, and CD62L and displayed low intracellular perforin content. In contrast, BLC-stimulated CTL could be generated from naive or memory CD8+ T cells and showed a more mature phenotype (low CD69, CD25, and CD62L with higher levels of perforin). The expansion of alloreactive T cells by EC stimulation was 5- to 20-fold less effective than in corresponding BLC-stimulated cultures, accounting for a reduction in the assayable cytotoxicity of individual microcultures. In these IL-2-supplemented cocultures, no effect on CTL generation or phenotype was observed by mAb blocking of costimulation provided by LFA-3, ICAM-1, or CD40, by addition of comitogenic anti-CD28 mAb, or by preactivation of EC with CD40 ligand. Cyclosporine inhibited CTL expansion and cytotoxicity similarly in both EC- and BLC-stimulated cultures but did not affect the phenotype of those CTL that did emerge. This study extends the characterization of endothelium as an immunoregulatory cell type distinct from conventional APC and may explain why graft rejection within the arterial intima, an anatomic compartment in which EC may be the primary type of APC, is separable from rejection in the graft parenchyma.

B-Lymphocytes↗
PubMed1983

The correlation between the activation state of B cells and their capacity for in vitro propagation of immunologic memory.

The B-cell population responsible for in vitro antigen-mediated proliferation and expansion of the memory B-cell population is a large activated blast. Such cells predominate early after antigen priming and can be regenerated by adjuvant (Bordetella pertussis) stimulation in vivo. Although these cells are proliferating in vivo, additional stimuli are needed for expansion of the memory population in vitro. These triggering requirements include specific antigen (DNP-OVA) and the assistance of adherent accessory cells. Although T cells are present in the culture, their role in the propagation of memory is not completely clear. Using the unrelated antigen, sheep erythrocytes, we have shown that "bystander" T-cell help can mediate differentiation of these memory B-cell blasts to AFC, but it cannot induce expansion of the memory-cell population. However, the fact that the TI-2 antigen DNP-Ficoll is a relatively ineffective inducer of memory-cell propagation (inducing an expanded response which is less than 10% of that induced by the T-cell-dependent antigen, DNP-OVA) suggests that T cells may be involved, possibly via production of B-cell growth factor. Thus, the minimal requirements for triggering the propagation of B-cell memory include (i) a blastogenic signal which can be mediated by adjuvant, (ii) specific antigen, and (iii) adherent accessory-cell help.

Animals↗
PubMed1996

The T cell-B cell interaction via OX40-OX40L is necessary for the T cell-dependent humoral immune response.

Recent in vitro studies have established that activated B cells express OX40 ligand (L), a member of the tumor necrosis factor/nerve growth factor family of cytokines, and become stimulated to proliferate and secrete immunoglobulin (Ig) after cross-linking of OX40L by its counterreceptor OX40, which is expressed on activated T cells. In the present study we investigated the in vivo role of this receptor-ligand pair for the interaction of T and B cells in the course of the T-dependent B cell response against 2,4,6 trinitro-phenyl-keyhole limpet hemocyanin. First, we showed that OX40 is maximally expressed by T cells in the periarteriolar lymphoid sheath (PALS) 3 d after primary immunization. These OX40+ cells are located in close proximity to antigen-specific, activated B cells. Second, we demonstrated that blocking of OX40-OX40L interaction with polyclonal anti-OX40 antibody or with antibodies against certain peptide sequences within its extracellular domain resulted in a profound decrease of the anti-hapten IgG response, whereas the antihapten IgM response was grossly unchanged. Third, we showed that this antibody treatment leads to an inhibition of the development of PALS-associated B cell foci, whereas the formation of germinal centers remained intact. Finally, our data suggest that, whereas B cell memory development was not impaired by anti-OX40 administration, OX40-OX40L interaction seems to be crucial in the secondary immune response. We conclude from these data that the OX40-OX40L interaction in vivo is necessary for the differentiation of activated B cells into highly Ig-producing cells, but is not involved in other pathways of antigen-driven B cell differentiation such as memory cell development in the germinal centers.

Animals↗
PubMed1993

Memory in idiotypic networks due to competition between proliferation and differentiation.

A model employing separate dose-dependent response functions for proliferation and differentiation of idiotypically interacting B cell clones is presented. For each clone the population dynamics of proliferating B cells, non-proliferating B cells and free antibodies are considered. An effective response function, which contains the total impact of proliferation and differentiation at the fixed points, is defined in order to enable an exact analysis. The analysis of the memory states is restricted in this paper to a two-species system. The conditions for the existence of locally stable steady states with expanded B cell and antibody populations are established for various combinations of different field-response functions (e.g. linear, saturation, log-bell functions). The stable fixed points are interpreted as memory states in terms of immunity and tolerance. It is proven that a combination of linear response functions for both proliferation and differentiation does not give rise to stable fixed points. However, due to competition between proliferation and differentiation saturation response functions are sufficient to obtain two memory states, provided proliferation precedes differentiation and also saturates earlier. The use of log-bell-shaped response functions for both proliferation and differentiation gives rise to a "mexican-hat" effective response function and allows for multiple (four to six) memory states. Both a primary response and a much more pronounced secondary response are observed. The stability of the memory states is studied as a function of the parameters of the model. The attractors lose their stability when the mean residence time of antibodies in the system is much longer than the B cells' lifetime. Neither the stability results nor the dynamics are qualitatively changed by the existence of non-proliferating B cells: memory states can exist and be stable without non-proliferating B cells. Nevertheless, the activation of non-proliferating B cells and the competition between proliferation and differentiation enlarge the parameter regime for which stable attractors are found. In addition, it is shown that a separate activation step from virgin to active B cells renders the virgin state stable for any choice of biologically reasonable parameters.

Animals↗
PubMed2003

Ex vivo characterization of human CD8+ T subsets with distinct replicative history and partial effector functions.

After antigenic challenge, naive T lymphocytes enter a program of proliferation and differentiation during the course of which they acquire effector functions and may ultimately become memory cells. In humans, the pathways of effector and memory T-cell differentiation remain poorly defined. Here we describe the properties of 2 CD8+ T-lymphocyte subsets, RA+CCR7-27+28+ and RA+CCR7-27+28-, in human peripheral blood. These cells display phenotypic and functional features that are intermediate between naive and effector T cells. Like naive T lymphocytes, both subsets show relatively long telomeres. However, unlike the naive population, these T cells exhibit reduced levels of T-cell receptor excision circles (TRECs), indicating they have undergone additional rounds of in vivo cell division. Furthermore, we show that they also share effector-type properties. At equivalent in vivo replicative history, the 2 subsets express high levels of Fas/CD95 and CD11a, as well as increasing levels of effector mediators such as granzyme B, perforin, interferon gamma, and tumor necrosis factor alpha. Both display partial ex vivo cytolytic activity and can be found among cytomegalovirus-specific cytolytic T cells. Taken together, our data point to the presence of T cells with intermediate effector-like functions and suggest that these subsets consist of T lymphocytes that are evolving toward a more differentiated effector or effector-memory stage.

Adult↗