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At least 757 records · Page 42Linked to original sources
PubMed2006

Phenotypic characterization of autoreactive T cells in multiple sclerosis.

MS has been hypothesized to result from autoreactive T cell responses against myelin antigens. In this report, we examined myelin-specific CD8 and CD4 T cells for two markers differentially expressed on naïve, memory and chronically stimulated T cells, CD28 and CD57. We observed differential expression on CD8 T cells in response to myelin antigens, but not in response to the recall antigen mumps. We demonstrate these cells display reduced proliferation and this may explain why therapies that limit the proliferation of T cells have had little effect on the course of MS, particularly later in the course of the disease.

Adult↗
PubMed2002

Interleukin 15 promotes antigen-independent in vitro expansion and long-term survival of antitumor cytotoxic T lymphocytes.

The survival and expansion of effector cytotoxic T lymphocytes (CTLs) during an immunological response are critical for the successful elimination of life-threatening attacks by microorganisms, parasites, or malignant cells. Among the numerous factors that regulate the immune response, interleukin (IL)-2, and its close relative, IL-15 are known to function as growth and survival factors for antigen-experienced T cells. However, major differences appear to exist between these lymphokines in their capacity to act on various T-cell types such as CD4+ versus CD8+ or effector versus memory T lymphocytes. Although several studies have been done in the mouse system, less information is available regarding the function of these lymphokines in the human system. Here, we report that IL-15 or high concentrations of IL-2 induced antigen-independent expansion of effector CD8+ CTLs. Neither IL-2 nor IL-15 induced the proliferation of CD4+ T cells. In the absence of antigen, at least one of these lymphokines was required for the long-term survival of the cells in tissue culture. Most significantly, the effector cytolytic activity of CTLs expanded and maintained in IL-15 for up to 60 days remained stable, indicating that these cells do not differentiate into a memory functional phenotype. The expression of IL-15Ralpha, which was detected on CD8+ CTLs but not on CD4+ helper T cells, suggests that this receptor subunit somehow participates in the transduction of the mitogenic signals of IL-15. The present findings have practical implications for the propagation of antigen-specific T-cell lines in vitro and could be useful for expansion of therapeutic T cells for adoptive transfer.

CD4-Positive T-Lymphocytes↗
PubMed1995

Differential regulation of molecular subtypes of muscarinic receptors in Alzheimer's disease.

Molecular subtypes of muscarinic receptors (m1-m5) are novel targets for cholinergic replacement therapies in Alzheimer's disease. However, the status of these receptors in human brain and Alzheimer's disease is incompletely understood. The m1-m5 receptors in brains from control subjects and Alzheimer's disease patients were examined using a panel of specific antisera and radioligand binding. Quantitative immunoprecipitation demonstrated a predominance of the m1, m2, and m4 receptor subtypes in cortical and subcortical regions in control subjects. In Alzheimer's disease, normal levels of m1 receptors measured by radioligand binding contrasted with decreased m1 receptor immunoreactivity, suggesting that the m1 receptor is altered in Alzheimer's disease. The m2 immunoreactivity was decreased, consistent with the loss of m2 binding sites and the location of this receptor subtype on presynaptic cholinergic terminals. The m4 receptor was up-regulated significantly and may offer a target for new memory-enhancing drugs. Differential alterations of molecular subtypes of muscarinic receptors may contribute to the cholinergic component of Alzheimer's disease dementia.

Aged↗
PubMed2002

[Chronic lymphoid leukemia: a single disease or 2 distinct diseases?].

Chronic Lymphocytic Leukemia (CLL) most commonly arises from a malignant clone of B cells with a characteristic phenotype, an autoreactive activity and an increased resistance to apoptosis. It is far from uniform in presentation and clinical course. About one-third of patients never require treatment and have a long survival; in another third an initial indolent phase is followed by progression of the disease; the remaining third of patients have aggressive disease at the outset and need immediate treatment. During recent years the development of biologic markers has allowed a better definition of prognosis in CLL. Serum levels of beta 2-microglobulin, LDH, and soluble CD23 can help predict disease activity, but the presence in the leukemic B cells of cytogenetic abnormalities like 11q or 11p deletions, the presence of the CD38 marker or somatic mutations in the immunoglobulin heavy chain genes are better predictors of rapid progression and survival. These recent results could suggest that there are two types of chronic lymphocytic leukemia: one arises from relatively less differentiated (immunologically naive) B cells with unmutated heavy chain genes, and has a poor prognosis; the other evolves from more differentiated B cells (memory B cells) with somatically mutated heavy chain genes, and has a good prognosis. However, all CLL patients share a same morphology, phenotype and overexpression of the bcl-2 and p27Kip1. In addition, recent data derived from gene expression profiling analysis failed to clearly distinguish unmutated and mutated cases and favor the view that all cases of CLL have a common cell origin and/or a common mechanism of malignant transformation.

Apoptosis↗
PubMed2005

Phosphorylation of extra-nuclear ERK/MAPK is required for long-term memory consolidation in the crab Chasmagnathus.

It was previously demonstrated that mitogen-activated protein kinase (MAPK) signaling plays a pivotal role in neural plasticity and memory processes both in rodents and mollusks. Although the MAPK pathways are highly conserved, no evidence was found for its participation in memory models in other animal groups. Here we found ERK-like and JNK-like cross-immunoreactivity in the crab brain with phospho-specific antibodies and we estimated ERK and JNK activity during long-term memory consolidation in the context-signal learning paradigm of the crab Chasmagnathus. At 0, 1, 3 and 6h after training ERK and JNK activity was measured. ERK-like activation was found 1h after spaced training in cytosolic but not in nuclear fractions of brain homogenates, while JNK activity remained unchanged in both fractions. Passive (context exposure) and active (continuous stimulation) controls showed cytosolic ERK and JNK activation immediately after training, which decayed 1h later. In coincidence with this time course of activity, an ERK1/2 pathway inhibitor, PD098059, induced amnesia only when administered 45 min after training but not when administered immediately pre- or post-training. These data support that: (1) cytoplasmic but not nuclear ERK substrates must be differentially phosphorylated during memory consolidation, and (2) ERK phosphorylation and consequent activation 1h after training is necessary for long-term memory consolidation in this arthropod model.

Amnesia↗
PubMed2004

Effects of neonatal lesions of the medial prefrontal cortex on adult rat behaviour.

While prefrontal lesions in rodents serve as models for frontal lobe syndromes, neonatal lesions are considered as models for disconnection syndromes, such as schizophrenia. We investigated the effect of neonatal lesions of the rat medial prefrontal cortex (mPFC) together with pubertal dexamethasone-challenge on adult rat behaviour and on apomorphine-induced behavioural changes. Adult lesions were used as controls. Rats with neonatal (postnatal day 7) or adult excitotoxic lesions or sham-lesions of the mPFC were tested 9 weeks after surgery. At postnatal day 49 one group of neonatal operated rats were systemically injected with the glucocorticoid receptor agonist dexamethasone (20 mg/kg), in order to simulate stress-induced glucocorticoid receptor activation. Working memory and perseveration was tested in T-maze tasks (continuous delayed alternation and reversal learning). Additionally, locomotor activity and prepulse inhibition (PPI) of startle was tested with and without apomorphine-treatment. Brain tissue damage was assessed using Nissl-staining and parvalbumine-immunocytochemistry. Pronounced thinning of the prelimbic-infralimbic subregion of the mPFC accompanied by altered cytoarchitecture and reduced number of parvalbumine-immunopositive neurones was found after neonatal lesions while adult lesions resulted in loss of neurones accompanied by gliosis. Neonatal lesions increased perseveration in the T-maze tasks and enhanced PPI, while adult lesions induced a working memory deficit. This differential behavioural outcome presumably reflects neurodevelopmentally induced alterations in neuronal circuits after neonatal lesions versus damage to mPFC alone after adult lesions. Dexamethasone-injection at day 49 did not alter behaviour in these tasks. Motor activity was not affected by neonatal or adult lesions but dexamethasone reduced apomorphine-induced hyperlocomotion.

Analysis of Variance↗
PubMedDate not supplied

Differentiation of human gamma-delta T cells towards distinct memory phenotypes.

Vgamma9/Vdelta2 T cells comprise a small population of peripheral T cells responding towards the low molecular weight antigen, (E)-4-hydroxy-3-methyl-but-2-enyl-pyrophosphate (HMB-PP). HMB-PP-stimulated Vgamma9/Vdelta2 T cells proliferated, expressed CCL5/RANTES, and upregulated markers like CD16, CD25, CD69, and CD94, in the presence of either IL-15 or IL-21. Vgamma9/Vdelta2 T cells grown in the presence of IL-15 differentiated into an effector/memory population characterized by production of TNF-alpha, expression of CD45RO and CCR5, and lack of CD62L, CD81, and CCR7. In contrast, Vgamma9/Vdelta2 T cells grown with IL-21 differentiated into putative central memory CD45RO(+) T cells that did not produce TNF-alpha, IFN-gamma, or IL-4, and maintained expression of CD62L, CD81, and CCR7.

Antigens, CD↗
PubMed2005

Modulation of memory CD4 T cell function and survival potential by altering the strength of the recall stimulus.

Optimization of long term immunity depends on the functional persistence of memory T cells; however, there are no defined strategies for promoting memory T cell function and survival. In this study, we hypothesized that varying the strength of the recall stimulus could modulate the function and survival potential of memory CD4 T cells. We tested the ability of peptide variants of influenza hemagglutinin (HA) exhibiting strong and weak avidity for an HA-specific TCR, to modulate HA-specific memory CD4 T cells in vitro and in vivo. In vitro stimulation with a weak avidity peptide (L115) uncoupled memory CD4 T proliferation from effector cytokine production with low apoptosis, whereas stimulation with a strong avidity peptide (Y117) fully recalled memory T cell functions but triggered increased apoptosis. To determine how differential recall would affect memory T cells in vivo, we boosted BALB/c hosts of transferred, CFSE-labeled HA-specific memory CD4 T cells with native HA, Y117, and L115 variant peptides and found differences in early Ag-driven memory T cell proliferation and IL-7R expression, with subsequent changes in memory T cell yield. High avidity boosting resulted in rapid proliferation, extensive IL-7R down-regulation, and the lowest yield of HA-specific memory cells, whereas low avidity boosting triggered low in vivo proliferation, maintenance of IL-7R expression, and the highest memory T cell yield. Our results indicate that memory CD4 T cell function and survival can be modulated at the recall level, and can be optimized by low level stimulation that minimizes apoptosis and enhances responses to survival factors.

Animals↗
PubMed2002

Leptin inhibits the anti-CD3-driven proliferation of peripheral blood T cells but enhances the production of proinflammatory cytokines.

There is increasing evidence that leptin affects immune responses and that in the absence of leptin, immunity is suboptimal. Most data so far indicate that leptin increases proinflammatory immune responses by an effect on T cells and macrophages. Here we show that, under certain circumstances, leptin can inhibit T cell proliferative responses. Separation of the responding T cells into different subpopulations revealed an interesting heterogeneity of cellular behavior in that naïve and memory T cells were differentially affected by leptin. The anti-CD3-driven proliferation of memory T cells was inhibited by leptin, whereas that of naïve T cells was markedly enhanced. Despite the inhibition of proliferation of the memory T cells, their production of interferon-gamma was substantially increased. These data show that leptin can inhibit certain immune responses in vitro. However, despite this inhibition of proliferation, the production of proinflammatory cytokines is significantly enhanced by leptin. The findings demonstrated here show further complexity in the actions of leptin on the immune system.

Animals↗
PubMed2004

Conscious processing of sexual information: mechanisms of appraisal.

To elucidate some of the activational mechanisms of sexual response, this study investigated the effects of conscious appraisal of sexual and neutral stimuli on a categorization task and on ratings of sexual arousal. Conscious appraisal is dependent on memory, regulatory, and attentional processes, interacting with one another. It is proposed that regulation is activated by attention, furnished by representations from implicit and explicit memory. Participants (26 men and 25 women) were asked to respond to "target" stimuli that were preceded by supraliminal "prime" stimuli. Primes and targets were operationalized by slides with sexual (i.e., romantic vs. explicit) and neutral content. In a cognitive task, participants had to group randomly presented targets as quickly as possible into sexual and nonsexual categories. Categorization of sexual targets was delayed when they were preceded by sexual primes compared to neutral primes. This was interpreted as an inhibitory process and compared with the Sexual Content-Induced Delay phenomenon (J. H. Geer & H. S. Bellard, 1996; J. H. Geer & J. S. Melton, 1997). No gender difference was found. In a subsequent affective task, participants provided an assessment of sexual arousal, followed by an evaluation of the target. This task was hypothesized to result in differential access to memory, where assessments of sexual arousal are influenced mainly by implicit memory, and where evaluations are influenced mainly by explicit memory. Gender differences were most prominent in the evaluation aspect of this task. It was concluded that cognitive processing of sexual information is similar for both genders, but that gender differences are present in affective processing of sexual information.

Adult↗
PubMed1998

Unilateral hippocampal lesions in newborn and adult rats: effects on spatial memory and BDNF gene expression.

Subcortical damage at birth often produces more severe deficits than similar lesions in an adult. In the present study, effects of unilateral electrolytic hippocampal ablations made on postnatal day 1 or in 3-month-old adult rats, were compared. Exploratory behavior and spatial navigation in the Morris water maze (MWM) were assessed 8 and 20 weeks after hippocampal damage. Rats with neonatal damage did not respond to novelty in the environment and did not learn to find the hidden platform in the MWM. Rats lesioned as adults did learn the water maze task, but slower than controls. We hypothesized that behavioral deficits observed in rats lesioned at birth, may be due, in part, to neurochemical dysfunction of the contralateral hippocampus. Specifically, cholinergic and GABAergic neurotransmission were assessed by measuring choline-acetyltransferase (ChAT) and GABAdecarboxylase (GAD) activity. In addition, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA levels were assayed in the remaining (contralateral) hippocampus. Of these molecules, only BDNF gene expression was significantly reduced (by 30%) at 8 and 20 weeks after neonatal and adult unilateral ablation. The similar reduction in BDNF mRNA in both treatment groups does not correspond with the lesion's differential effect on memory function. However, the more severe learning impairment after neonatal lesion may reflect increased dependence on trophins during development.

Aging↗
PubMed1999

Adjuvant-guided type-1 and type-2 immunity: infectious/noninfectious dichotomy defines the class of response.

Traditionally, protein Ags have been injected in CFA (oil with inactivated mycobacteria) to induce immunity and with IFA (oil alone) to induce tolerance. We report here that injection of hen eggwhite lysozyme, a prototypic Ag, in CFA-induced and IFA-induced pools of hen eggwhite lysozyme-specific memory T cells of comparable fine specificity, clonal size, and avidity spectrum, but with type-1 and type-2 cytokine signatures, respectively. This adjuvant-guided induction of virtually unipolar type-1 and type-2 immunity was observed with seven protein Ags and in a total of six mouse strains. Highly polarized type-1 and type-2 immunity are thus readily achievable through the choice of adjuvant, irrespective of the genetic bias of the host and of the nature of the protein Ag. This finding should have far-reaching implications for the development of vaccines against infectious and autoimmune diseases. Furthermore, our demonstration that Ag injected with IFA is as strongly immunogenic for T cells as it is with CFA shows that the presence of the mycobacteria determines not the priming of naive T cells through the second-signal link but the path of downstream differentiation toward CD4 memory cells that express either type-1 or type-2 cytokines.

Alum Compounds↗
PubMed2002

Differential in vivo persistence of two subsets of memory phenotype CD8 T cells defined by CD44 and CD122 expression levels.

The existence of distinct subsets of memory CD8 T cells with different characteristics is now well established. In this work, we describe two subsets of mouse CD8 T cells with memory characteristics that coexist in primed thymectomized TCR-transgenic F5 mice and that share some properties with the human central and effector memory cells. The first subset corresponds to CD8 T cells generated following nucleoprotein 68 peptide priming which are CD44(int)CD122(-)nucleoprotein 68/H-2D(b) tetramer(+) and express high levels of CCR7 mRNA. In contrast, CD8 T cells in the second subset are CD44(high)CD122(+), are heterogeneous in terms of Ag specificity, and express low levels of CCR7 mRNA. We have studied the functional characteristics and the persistence of these two subsets in thymectomized mice. CD44(int) CD8 T cells persist like naive cells; i.e., they are slowly lost with time. However, surviving cells maintain their phenotype and memory characteristics for the entire life span of the animal. In contrast, CD44(high) CD8 T cells are persistent and accumulate in thymectomized but not euthymic mice. This is correlated with an increased in vivo proliferative and survival potential of these cells. These results show that acquisition of enhanced functional characteristics and long-term persistence by memory T cells are independent. This may have important consequences for the design of specific vaccine.

Animals↗
PubMed2000

The effect of TGF-beta1 on immune responses of naïve versus memory CD4+ Th1/Th2 T cells.

The role of TGF-beta1 in the regulation of T cell responses has been perplexing, possibly because it is dependent on the type of T cell being regulated and its cytokine microenvironment. In the present study, we demonstrate that TGF-beta1 has a profound inhibitory effect on naive CD4+ T cell undergoing differentiation under defined neutral, Th1 and Th2 priming conditions. In addition, we show that if CD4+ T cells are primed in the presence of TGF-beta1, they exhibit reduced secondary anti-CD3/anti-CD28-induced and antigen-specific immune responses (even when TGF-beta is absent during the secondary response), which is not due to reduced expression of co-stimulatory molecules or to inadequate IL-2 production. Finally, with respect to the effect of TGF-beta on fully differentiated antigen-specific memory CD4+ T cells, we demonstrate that while antigen-specific activation and cytokine secretion by memory Th1 T cells is inhibited by TGF-beta1, such inhibition is associated with partial down-regulation of IL-12 receptor beta2 chain expression. In contrast, memory Th2 T cells are not subject to TGF-beta1 -mediated suppression. In summary, these studies reveal that TGF-beta1 is a powerful negative regulator of the primary immune response of CD4+ T cells, but only Th1 T cells are subject to such regulation after the memory stage of T cell differentiation has been reached. Thus, these studies define the potential regulatory role of TGF-beta1 in Th1 and Th2 T cell-mediated autoimmunity.

Animals↗
PubMed1986

Retrieval variability: sources and consequences.

A memory model that differentiates between active traces (ongoing electrochemical neural transmission) and passive traces (chemical/structural modification of neurons) is briefly outlined. Evidence suggests that new information is initially encoded as a passive representation within a fraction of a second, leaving little opportunity for retroactive interference with storage processes. Instead, it appears that retroactive interference results from disruption of post-acquisition processing which is necessary for subsequent retrieval. Using this hybrid cognitive-physiological framework, we examine possible sources of associative performance deficits. A distinction is made between similarity interference (arising from the content similarity of the target and interfering traces) and processing interference (arising from the competition between the two traces for use of a limited capacity processor). Both types of interference can act proactively or retroactively, and the similarity-processing and proactive-retroactive dimensions are viewed as orthogonal to the question of whether information is permanently lost or merely subject to a reversible retrieval failure. When reminder techniques (pretest cuing) are used, numerous instances of memory failure commonly identified as "acquisition failures" are found to be reversible without the occurrence of relevant new learning. This literature review constitutes the greater part of the paper. It is concluded that many memory failures are due at least in part to retrieval failure. Consideration of potential retrieval processes in light of the studies that are reviewed argues for the expansion of the initial active-passive trace distinction to three types of traces. In addition to active traces, these include two distinct types of passive traces, i.e., a small content-addressable reference catalog with innately defined dimensions that is used to locate more detailed passive traces, and a large capacity store of detailed passive traces that is location-addressable. The latter type of passive trace presumably is laid down almost instantaneously as events occur, i.e., in real time, whereas the reference catalog type of passive trace, which is used to address the detailed traces, is established somewhat after the sequence of events is complete. Hence, the reference catalog trace is more vulnerable and results in retrieval failure when it is disrupted.(ABSTRACT TRUNCATED AT 400 WORDS)

Amnesia↗
PubMed1986

Effects of altered cholinergic function on working and reference memory in the rat.

Many data suggest that the brain's cholinergic neurons participate in the control of memory and it has been suggested that cholinergic systems are involved differentially in working and reference memory. To test this hypothesis the effects on memory of unilateral injections of the neurotoxins, quinolinic acid or kainic acid into the cortically projecting cholinergic cells of the nucleus basalis magnocellularis (nbm) were evaluated. In experiment 1, quinolinate-injected (n = 7) and sham-operated (n = 7) rats were tested in a T-maze alternation task that requires working memory. Lesion rats performed significantly more poorly than shams and subsequent biochemical assays of cortical choline acetyltransferase (CAT) activity revealed significant reductions in the lesion rats. In experiment 2, kainate-injected (n = 9) and sham-operated (n = 8) rats were trained in an eight-arm radial maze with only four arms baited. Lesion rats made significantly more working memory errors (entries into baited arms from which the food had already been collected) than reference memory errors (entries into never baited arms). CAT assays showed that the lesion led to a decrease in cortical CAT with no significant change in hippocampal CAT. The results of these studies support the hypothesis that cholinergic neurons of the basocortical system may be differentially involved in working and reference memory.

Animals↗
PubMed1999

The effects of high fat diets and environmental influences on cognitive performance in rats.

As part of a continuing investigation of the relationship between dietary factors and cognitive function, the present study examined the combined effects of environmental influences and high-fat diets on learning and memory. Following 3 months of dietary (20% by weight fat diets, composed primarily of either beef tallow or soybean oil versus standard laboratory chow) and environmental treatments (standard, enriched or impoverished), subjects were tested on a variable interval delayed alternation (VIDA) task which measures learning and memory functions that differentially involve specific brain regions. The results confirmed the negative effects of high fat diets, relative to chow, on all aspects of VIDA performance and showed that environmental enrichment overcame deficits associated with dietary fat. Housing rats fed high-fat diets in an impoverished environment did not further exacerbate cognitive deficits observed in such rats living under standard conditions. By comparison, chow-fed rats exhibited no benefit associated with the enriched environment on any aspect of task performance, and only a transitory learning impairment when housed in an impoverished environment. The results show that high fat diets and environmental conditions influence cognitive function and that these two factors interact with one another to produce different profiles of benefits and impairments.

Animals↗
PubMed1983

Effects of lateral reversal on recognition memory for photographs of faces.

Recognition memory for photographs of faces, which were initially shown in the normal orientation, then tested either normally (unchanged) or laterally reversed (changed), was examined in four experiments involving different experimental designs (between and within group) and different methods of testing (yes-no and forced-choice). Although the overall effect of the transformation was not as powerful as others (e.g. hair style change) which have been applied to faces, and even failed to attain statistical significance in a fifth experiment in which all the photographs were initially reversed at presentation then tested unchanged or changed back to their normal orientation, the main findings were as follows: (a) subjects recognized fewer reversed (changed) than normal (unchanged) photographs whether or not they were informed of the transformation; (b) the adverse effect of reversal occurred on faces looking straight ahead (full-faces) and, to a slightly lesser extent, on those looking to the left of the observer (left-lookers); (c) left-lookers and right-lookers (the left-lookers initially reversed in Expt 5) were less well recognized than full-faces; and (d) subjects had difficulty identifying orientation, where accuracy fell almost to chance level. These results are taken as support for a feature (rather than Gestalt) model of facial recognition in which the two sides of the face are differentiated in its memory representation.

Adolescent↗