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PubMed2006

[Changes of NMDA receptor expression in rat hippocampal formation after establishment of spatial memory by different training modes].

There is no unambiguous report so far on whether short reinforcing training could establish stable spatial long-term memory and how the NMDA/NR1 expression in the hippocampal formation changes after establishment of short- and long-term memory. In the present study, three spatial memory training modes of Morris water maze were used: spatial long-term memory training mode (LT group), spatial short-term memory training mode (ST group) and short reinforcing training mode (SRT group). The characteristics of those memories established by different training modes were compared. The immunofluorescence histochemical staining technique was used to observe the changes of NMDA/NR1 expression in the hippocampal formation in the three groups. The results showed that, during Morris water maze training, no significant difference was found in the mean latency and the strategies to the target between the LT and SRT groups. The examination of the memories following different trainings indicated that the mean latency and the strategies to the target as well as the times crossing the target in LT group were not significantly different from those in SRT group, except that the mean time remaining in the platform quadrant in LT group was significantly longer than that in SRT group. In addition, no significant difference in the intensity of NMDA/NR1 immunoreactivity in CA1, CA3 and dentate gyrus of the hippocampal formation was observed between the control and ST groups or between LT and SRT groups. However, the intensity of NMDA/NR1 immunoreactivity in CA1 area and dentate gyrus in both LT and SRT groups was significantly increased as compared with that in ST or the control groups. These results suggest that the short reinforcing training mode can establish long-term spatial memory, which is almost the same as that established by the long-term training mode, and that the increase of NMDA/NR1 expression in CA1 area and dentate gyrus of the hippocampal formation may be one of the mechanisms of spatial long-term memory formation.

Animals↗

PubMed1980

Partial report and other sampling procedures overestimate the duration of iconic memory.

In three experiments, subjects estimated the duration of a brief visual image (iconic memory) either directly by adjusting onset of a click to offset of the visual image, or indirectly with a Sperling partial report (sampling) procedure. The results indicated that partial report and other sampling procedures may reflect other brief phenomena along with iconic memory. First, the partial report procedure yields a greater estimate of the duration of iconic memory than the more direct click method. Second, the partial report estimate of the duration of iconic memory is affected if the subject is required to simultaneously retain a list of distractor items (memory load), while the click method estimate of the duration of iconic memory is not affected by a memory load. Finally, another sampling procedure based on visual cuing yields different estimates of the duration of iconic memory depending on how many items are cued. It was concluded that partial report and other sampling procedures overestimate the duration of iconic memory.

Attention↗

PubMed1997

[Memory training for remembering names: initial results in the healthy elderly].

In this study, a memory training program for remembering names was developed. It was assumed that names are remembered better if they have meaning. The effect of training is compared with two control conditions a) a placebo training, aimed at reducing worries about forgetfulness by giving information about memory and aging and b) a retest control group. Participants were healthy persons over 43 years old (M = 70 years) having subjective memory complaints and objective memory problems. The effect of training is evaluated with tasks for remembering names. Because the learned memory strategy can be applied to these tasks, these are called target memory tests. Other evaluation measures concerned remembering verbal information and intentions. These are called control memory tests, because the memory strategy learned cannot be applied directly. In accordance with the expectations, performance in the placebo training group (n = 10) did not improve more than in the retest control group (n = 11). The names training group (n = 13) improved more than both control groups on tests for remembering names. This improvement was maintained for at least three months after training. As expected, the improvement in performance on the target memory tests did not generalize to the control tasks, because of the specificity of the learned strategies.

Aged↗

PubMed1993

Memory evaluation in Alzheimer's disease. Caregivers' appraisals and objective testing.

OBJECTIVES: To evaluate if caregivers are reliable informants concerning memory deficits in patients with Alzheimer's disease (AD). DESIGN: Responses of caregivers of patients with probable AD and responses of healthy control subjects on a standardized memory questionnaire were compared with objective measures of cognition (Consortium to Establish a Registry for Alzheimer's Disease neuropsychological battery) and with clinical estimates of activities of daily living, depression, and psychopathology (Consortium to Establish a Registry for Alzheimer's Disease [CERAD] clinical assessment battery) using the Self-report Memory Questionnaire. SETTING: A federally funded AD research center. SUBJECTS: The referred sample included 117 patients with probable AD, their informants, and 41 healthy control subjects age-matched to the patients. Patients and control subjects were between the ages of 58 and 85 years, had between 9 and 19 years of education, and were in good health. EXCLUSIONS: Patients who did not meet NINCDS-ADRDA criteria of probable AD. MAIN OUTCOME MEASURE: The optimal number of questionnaire items yielding the best combination of sensitivity and specificity. RESULTS: An abbreviated version of the scale, renamed the Short-Memory Questionnaire, had excellent specificity and sensitivity for identifying dementia. Positive and negative predictive values were 63.5% and near 100%, respectively. The Short-Memory Questionnaire showed good reliability, internal consistency, and external validity. Caregiver appraisals of memory deficits significantly correlated with objective measures of memory and also with generalized cognitive dysfunction. CONCLUSIONS: Caregivers of patients with AD are reliable informants of their relatives' deficits. The Short-Memory Questionnaire is an easily administered, informant-based scale that may be useful in clinical settings or epidemiologic studies to screen out persons with memory difficulties.

Aged↗

PubMed1994

Stimulus timing effects on Wada memory testing.

OBJECTIVE: To determine the effects of presenting Wada memory stimuli at different times after intracarotid amobarbital injection on Wada memory asymmetries. DESIGN: Wada memory asymmetries from three timing series were related to the laterality of eventual temporal lobectomy. SETTING: Academic institution epilepsy surgery program. PATIENTS: Forty-three patients with complex partial seizures who later underwent anterior temporal lobectomy (left temporal lobectomy, 24 patients; right temporal lobectomy, 19 patients). No patient included had abnormalities on magnetic resonance imaging scans to suggest a lesion other than gliosis. RESULTS: Memory performance for objects whose presentation began approximately 45 seconds after amobarbital administration differentiated laterality of seizure onset. Memory for items presented later and after partial return of language (on average 3 minutes 40 seconds postinjection) also differed as a function of ipsilateral vs contralateral injection, but at a lower level of statistical significance. Memory for items presented last during the procedure (on average 6 minutes postinjection) discriminated seizure groups at a still lower level of statistical significance. When used to predict lateralized temporal lobe impairment in individual patients, early object memory performance was significantly better than memory performance employing either middle (56%) or late (43%) stimulus presentation timings. CONCLUSION: The results of early object memory testing are superior to those obtained from stimulus presentation later in the procedure in documenting temporal lobe dysfunction associated with a lateralized seizure onset.

Adult↗

PubMed1999

Enhancement of memory in Alzheimer disease with insulin and somatostatin, but not glucose.

BACKGROUND: Increasing plasma glucose levels improves memory in patients with Alzheimer disease (AD). Increasing plasma glucose levels also increases endogenous insulin levels, raising the question of whether memory improvement is due to changes in insulin, independent of hyperglycemia. We address this question by examining memory and counterregulatory hormone response during hyperglycemia when endogenous insulin was suppressed by concomitant infusion of the somatostatin analogue octreotide (Sandostatin). METHODS: Twenty-three patients with AD and 14 similarly aged healthy adults participated in 4 metabolic conditions on separate days: (1) hyperinsulinemia (538 pmol/L) with fasting glucose (5.6 mmol/L [100 mg/dL]), achieved by insulin and variable dextrose infusion; (2) hyperglycemia (12.5 mmol/L [225 mg/dL]) with fasting insulin (57 pmol/L), achieved by dextrose and somatostatin (octreotide) infusion (150 mg/h); (3) placebo with isotonic sodium chloride solution (saline) infusion (fasting insulin and glucose); and (4) an active control condition in which somatostatin alone was infused (150 mg/h). Declarative memory (story recall) and selective attention (Stroop interference test) were measured during steady metabolic states. RESULTS: Patients with AD showed improved memory during hyperinsulinemia relative to placebo (P = .05) and relative to hyperglycemia (P<.005). Memory did not improve during hyperglycemia when insulin was suppressed. Somatostatin analogue infusion alone also improved memory for patients with AD (P<.05). Hyperinsulinemia increased cortisol levels in subjects with AD, whereas somatostatin alone lowered cortisol concentrations. CONCLUSIONS: These results confirm that elevated insulin without hyperglycemia enhances memory in adults with AD, and indicate that insulin is essential for hyperglycemic memory facilitation. These results also suggest a potential therapeutic role for somatostatin in AD.

Adult↗

PubMed2000

Memory performance and the apolipoprotein E polymorphism in a community sample of middle-aged adults.

The apolipoprotein E genotype (APOE) is an established risk factor for Alzheimer disease, with the age-at-onset occurring earlier in individuals having at least one APOE epsilon 4 allele, relative to the APOE epsilon 3 or APOE epsilon 2 isoforms. Moreover, nondemented older adults with the APOE epsilon 4 allele also show diminished cognitive performance, particularly on tests of learning and memory, and an accelerated decline in memory performance with increasing age. The current investigation extends the study of the APOE epsilon 4 allele and cognitive performance to healthy, middle-aged adults. A community sample of 220 non-Hispanic Caucasian men and women, aged 24-60 (average age = 46), were genotyped for the APOE polymorphism and completed a battery of neuropsychological tests. Multivariate analyses were conducted on measures of verbal learning and memory (e. g., learning a list of words and recalling them 30 min later), visual memory (e.g., reproducing a previously copied figure from memory), and attention span (e.g., repeating long lists of digits), after adjustments for age, and estimated IQ. Results indicated that performance on learning and memory tasks was significantly poorer in adults having any APOE epsilon 4 allele, relative to adults with APOE epsilon 2 and epsilon 3 genotypes (P <.01). Attention span did not differ by genotype. These findings, the first in a sample of middle-aged adults, suggest that the APOE polymorphism is a marker for age-related decline in memory (detectable prior to overt, clinical manifestations of memory loss), and/or a marker for individual differences in memory ability across the life span. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:707-711, 2000.

Adult↗

PubMed2000

Functional neuroimaging of memory: implications for cognitive aging.

Our understanding of the ways in which changes in specific neural systems mediate adult age differences in memory is rapidly increasing, due in no small part to the advent of functional neuroimaging techniques. This article reviews age-related changes in memory performance obtained with behavioral measures, describes models of the neural mechanisms of memory, and derives predictions from these models regarding age-related changes in brain activation patterns. The neuroimaging findings obtained to date support models emphasizing the role of prefrontal cortex in age-related changes in memory functioning, especially for episodic memory retrieval. In general, neural activation associated with episodic memory encoding is regionally similar for younger and older adults but relatively lower in magnitude for older adults. During retrieval, activation that is restricted to the right prefrontal cortex for younger adults is more likely to be bilateral for older adults. Prefrontal activation exhibits an age-related increase when working memory tasks require simple storage and an age-related decrease when working memory requires higher-level executive processes. Although the evidence is limited, behavioral performance and activation patterns appear to be similar among younger and older adults on tests of semantic (context-independent) and implicit memory. We conclude that several methodological issues, such as defining the relation between brain structure and function, and determining the relationship between performance and activation, are particularly important for understanding age-related changes. Future directions for aging research include further investigation of the relation between encoding and retrieval and the identification of both spared and impaired neural systems.

Adult↗

PubMed2000

Multiple trace theory of human memory: computational, neuroimaging, and neuropsychological results.

Hippocampal-neocortical interactions in memory have typically been characterized within the "standard model" of memory consolidation. In this view, memory storage initially requires hippocampal linking of dispersed neocortical storage sites, but over time this need dissipates, and the hippocampal component is rendered unnecessary. This change in function over time is held to account for the retrograde amnesia (RA) gradients often seen in patients with hippocampal damage. Recent evidence, however, calls this standard model into question, and we have recently proposed a new approach, the "multiple memory trace" (MMT) theory. In this view, hippocampal ensembles are always involved in storage and retrieval of episodic information, but semantic (gist) information can be established in neocortex, and will survive damage to the hippocampal system if enough time has elapsed. This approach accounts more readily for the very long RA gradients often observed in amnesia. We report the results of analytic and connectionist simulations that demonstrate the feasibility of MMT. We also report a neuroimaging study showing that retrieval of very remote (25-year-old) memories elicits as much activation in hippocampus as retrieval of quite recent memories. Finally, we report new data from the study of patients with temporal lobe damage, using more sensitive measures than previously the case, showing that deficits in both episodic and spatial detail can be observed even for very remote memories. Overall, these findings indicate that the standard model of memory consolidation, which views the hippocampus as having only a temporary role in memory, is wrong. Instead, the data support the view that for episodic and spatial detail the hippocampal system is always necessary.

Epilepsy, Temporal Lobe↗

PubMed2000

Patterns of hippocampal-cortical interaction dissociate temporal lobe memory subsystems.

A distributed network of brain regions supports memory retrieval in humans, but little is known about the functional interactions between areas within this system. During functional magnetic resonance imaging (fMRI), subjects retrieved real-world memories: autobiographical events, public events, autobiographical facts, and general knowledge. A common memory retrieval network was found to support all memory types. However, examination of the correlations (i.e., effective connectivity) between the activity of brain regions within the temporal lobe revealed significant changes dependent on the type of memory being retrieved. Medially, effective connectivity between the parahippocampal cortex and hippocampus increased for recollection of autobiographical events relative to other memory types. Laterally, effective connectivity between the middle temporal gyrus and temporal pole increased during retrieval of general knowledge and public events. The memory types that dissociate the common system into its subsystems correspond to those that typically distinguish between patients at initial phases of Alzheimer's disease or semantic dementia. This approach, therefore, opens the door to new lines of research into memory degeneration, capitalizing on the functional integration of different memory-involved regions. Indeed, the ability to examine interregional interactions may have important diagnostic and prognostic implications.

Adult↗

PubMed2000

Cognitive rehabilitation for memory deficits following stroke.

BACKGROUND: Memory problems occur following stroke. Cognitive rehabilitation programmes are provided to retrain memory function or to teach patients strategies to cope despite memory impairment. OBJECTIVES: To determine the effects of cognitive rehabilitation for memory problems following stroke. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register, Medline, EMBASE, CINHAL and CLIN PSYCH databases and reference lists from relevant articles. Date of most recent searches: December 1998. SELECTION CRITERIA: Controlled trials of memory retraining in stroke. Studies with mixed aetiology groups were excluded unless they had more than 75% of stroke patients or separate data were available for the stroke patients. DATA COLLECTION AND ANALYSIS: Two reviewers extracted trial data and assessed trial quality. Reviewers contacted investigators for further details of trials. MAIN RESULTS: One trial was identified with 12 participants. This showed memory strategy training had no significant effect on memory impairment or subjective memory complaints. REVIEWER'S CONCLUSIONS: There is insufficient evidence to support or refute the effectiveness of cognitive rehabilitation for memory problems after stroke.

Attention↗

PubMed2002

Interaction of cognitive aging and memory deficits related to epilepsy surgery.

Temporal lobe epilepsy surgery can cause significant memory impairment. This study was intended to examine whether surgery also could affect prognosis of memory in older age. Age regression of verbal memory was examined in 187 patients (before and 1 year after left temporal lobe surgery) and 264 healthy controls. Eighty patients underwent selective amygdalohippocampectomy, and 107 patients underwent anterior two-thirds temporal lobectomy. Amygdalohippocampectomy patients had mesiotemporal epilepsy; anterior two-thirds temporal lobectomy patients had more extramesial or diffuse seizure onset zones. Memory was assessed by word list learning for its more mesial (consolidation/retrieval) and more neocortical (learning) aspects. Patients showed significant preoperative memory impairment. Independent of seizure outcome and surgical approach, surgery had significant negative effects on learning and consolidation/retrieval. In the amygdalohippocampectomy group, preoperative and postoperative age regressions of learning and consolidation/retrieval were not different from those of controls. In the anterior two-thirds temporal lobectomy group, age regression of verbal learning became steeper after surgery, and consolidation/retrieval was negatively correlated with older age and later onset of epilepsy even before surgery. The data confirm that age regression of verbal memory in left temporal lobe epilepsy is similar to that in healthy controls. Both left anterior two-thirds temporal lobectomy and amygdalohippocampectomy worsen verbal learning and memory and bring patients closer to cognitive disability. Particularly in anterior two-thirds temporal lobectomy patients, surgery and reduced capacities for compensation cause acceleration of lifetime memory decline. The results support earlier and tailored epilepsy surgery and suggest that memory prognosis in older age should be considered if more extensive temporal resections would be inevitable.

Adolescent↗

PubMed2004

Altered blood B lymphocyte homeostasis in systemic sclerosis: expanded naive B cells and diminished but activated memory B cells.

OBJECTIVE: To determine phenotypic and functional abnormalities of blood B cell subsets in patients with systemic sclerosis (SSc). METHODS: Cell surface marker expression was determined by flow cytometry. Spontaneous apoptosis was evaluated by annexin V expression with flow cytometric analysis. IgG production by isolated IgD- memory B cells was examined by enzyme-linked immunosorbent assay. RESULTS: The numbers of blood CD27- naive B cells from SSc patients were increased compared with normal control cells, while memory B cells expressing medium levels of CD27 and plasmablasts expressing high levels of CD27 were reduced. In contrast, plasmablasts were the predominant population in patients with systemic lupus erythematosus (SLE). Memory B cells in SSc showed increased expression of activation markers, including CD80, CD86, and CD95, relative to normal controls. Consistent with CD95 up-regulation, SSc memory B cells exhibited augmented spontaneous apoptosis after 24-hour incubation; augmented apoptosis may explain the reduced memory B cell number. Nonetheless, isolated IgD- SSc memory B cells treated with stimuli had an enhanced ability to produce IgG. Furthermore, expression of CD19, a critical signal transduction molecule of B cells that regulates autoantibody production, was significantly increased in memory B cells as well as in naive B cells in SSc. In contrast, CD19 expression was decreased in SLE B cells. CONCLUSION: SSc patients have distinct abnormalities of blood homeostasis and B cell compartments, characterized by expanded naive B cells and activated but diminished memory B cells. Our results suggest that CD19 overexpression in SSc memory B cells is related to their hyperreactivity.

Adult↗

PubMed2006

Children's memory for a mild stressor: the role of sympathetic activation and parasympathetic withdrawal.

Although numerous studies have examined the relations between stress and memory in children, few studies have investigated physiological responses as predictors of children's memory for stressful events. In this study, 4- to 8-year-olds completed laboratory challenges and experienced a fire-alarm incident while their sympathetic and parasympathetic reactions were monitored. Shortly afterward, children's memory of the alarm incident was tested. As children's age and family income increased, memory performance improved. High sympathetic activation during the laboratory challenges was associated with enhanced memory. Also, a trend indicated that, among older children, greater general parasympathetic withdrawal was associated with poorer memory, but among younger children, parasympathetic withdrawal was unrelated to memory. Findings highlight the need to measure both sympathetic and parasympathetic responses when evaluating children's memory for mild stressors and to include a wide age range so that developmental changes in the relations between stress and memory in childhood can be identified.

Age Factors↗

PubMed1990

Inverse relationship of CA2+ mobilization and cell proliferation in CD8+ memory and virgin T cells.

Memory T cells can now be defined with various monoclonal antibodies but little is known about the functional properties of these cells as compared to virgin T cells. We have studied Ca2+ mobilization and proliferation of memory and virgin cells in both the CD4 and CD8 subsets in response to phytohemagglutin-in. Using two-color fluorescence (yellow, red) for cell surface staining combined with two-color fluorescence for the Ca2+ chelator indo-1 (violet, blue) we can demonstrate that CD8+UCHL1+ memory cells exhibit a 1,5-fold higher influx than the CD8+UCHL1- virgin cells. The same pattern was obtained when CD8 memory and virgin cells were defined by a reciprocal marker (Leu-18) indicating that the higher response of memory CD8 cells is independent of the monoclonal antibody used to identify the cells. For the respective CD4 subsets no such clear-cut pattern of Ca2+ influx was evident. Analysis of proliferation in both subsets indicates that CD8+UCHL1- cells strongly proliferate in response to PHA, while CD8+UCHL1+ memory cells show only a minimal response with the average cpm values being 6-fold lower. In some instances no proliferation at all was detectable in the CD8+UCHL1+ cells. Identification of the subsets by reciprocal markers confirmed the lower proliferative response in the CD8 memory cells. Hence, within the CD8 compartment the memory cells, after phytohemagglutinin stimulation, exhibit a high Ca2+ mobilization but a low to absent proliferation, while the converse is true for the naive cells. These data show that (a) Ca2+ mobilization and proliferation are inversely correlated and (b) an initially vigorous response of memory cells may be subject to negative control mechanisms.

Antigens, Differentiation↗

PubMed1996

The differentiation of human memory B cells into specific antibody-secreting cells is CD40 independent.

It is generally accepted that memory B cells can be defined by their ability to produce, upon antigenic challenge, somatically mutated antibody molecules characterized by an increased affinity and by the expression of a downstream heavy chain isotype. However, the inability to isolate this particular B cell compartment has precluded the study of memory B lymphocyte physiology in man. We previously reported on the identification of an IgD- B cell subset in human tonsils that we defined as CD38- B cells, whose phenotype is highly reminiscent of that of memory B lymphocytes from the splenic marginal zone of rodents. In the present study, we developed a model of the measles virus (MV)-specific secondary antibody response in vitro to assess the presence of memory B lymphocytes in different B cell subsets isolated from human tonsils and explore the activation requirements of human memory B cells. Our findings show that the memory B cell pool resides in the CD38- B cell subpopulation and that the differentiation of MV-activated memory B cells into antibody-secreting cells can be achieved upon co-stimulation with interleukin (IL)-2 and IL-10, but does not require engagement of CD40. Interestingly, the CD40-mediated signal was found to synergize with Ig-cross-linking agents for the proliferation of memory B cells, but strongly suppressed their capacity to differentiate along the plasmacytoid pathway. Collectively, our results suggest that the CD40 signaling pathway is instrumental for the clonal expansion of the memory B cell pool, but does not operate in the later phase of the response, which allows their maturation into antibody-secreting cells.

Antibodies, Viral↗

PubMed1997

Differential T cell receptor-mediated signaling in naive and memory CD4 T cells.

Naive and memory CD4 T cells differ in cell surface phenotype, function, activation requirements, and modes of regulation. To investigate the molecular bases for the dichotomies between naive and memory CD4 T cells and to understand how the T cell receptor (TCR) directs diverse functional outcomes, we investigated proximal signaling events triggered through the TCR/CD3 complex in naive and memory CD4 T cell subsets isolated on the basis of CD45 isoform expression. Naive CD4 T cells signal through TCR/CD3 similar to unseparated CD4 T cells, producing multiple tyrosine-phosphorylated protein species overall and phosphorylating the T cell-specific ZAP-70 tyrosine kinase which is recruited to the CD3zeta subunit of the TCR. Memory CD4 T cells, however, exhibit a unique pattern of signaling through TCR/CD3. Following stimulation through TCR/CD3, memory CD4 T cells produce fewer species of tyrosine-phosphorylated substrates and fail to phosphorylate ZAP-70, yet unphosphorylated ZAP-70 can associate with the TCR/CD3 complex. Moreover, a 26/28-kDa phosphorylated doublet is associated with CD3zeta in resting and activated memory but not in naive CD4 T cells. Despite these differences in the phosphorylation of ZAP-70 and CD3-associated proteins, the ZAP-70-related kinase, p72syk, exhibits similar phosphorylation in naive and memory T cell subsets, suggesting that this kinase could function in place of ZAP-70 in memory CD4 T cells. These results indicate that proximal signals are differentially coupled to the TCR in naive versus memory CD4 T cells, potentially leading to distinct downstream signaling events and ultimately to the diverse functions elicited by these two CD4 T cell subsets.

Amino Acid Sequence↗

PubMed1997

CD4+ T cells of both the naive and the memory phenotype enter rat lymph nodes and Peyer's patches via high endothelial venules: within the tissue their migratory behavior differs.

It is thought that naive T cells predominantly enter lymphoid organs such as lymph nodes (LN) and Peyer's patches (PP) via high endothelial venules (HEV), whereas memory T cells migrate mainly into non-lymphoid organs. However, direct evidence for the existence of these distinct migration pathways in vivo is incomplete, and nothing is known about their migration through the different compartments of lymphoid organs. Such knowledge would be of considerable interest for understanding T cell memory in vivo. In the present study we separated naive and memory CD4+ T cells from the rat thoracic duct according to the expression of the high and low molecular weight isoforms of CD45R, respectively. At various time points after injection into congenic animals, these cells were identified by quantitative immunohistology in HEV, and T and B cell areas of different LN and PP. Three major findings emerged. First, both naive and memory CD4+ T cells enter lymphoid organs via the HEV in comparable numbers. Second, naive and memory CD4+ T cells migrate into the B cell area, although in small numbers and continuously enter established germinal centers (GC) with a bias for memory CD4+ T cells. Third, memory CD4+ T cells migrate faster through the T cell area of lymphoid organs than naive CD4+ T cells. Thus, our study shows that memory CD4+ T cells are not excluded from the HEV route. In addition, "memory" might depend in part on the ability of T cells to specifically enter the B cell area and GC and to screen large quantities of lymphoid tissues in a short time.

Animals↗