Central Memory (central + memory)

Distribution by Scientific Domains
Medical Sciences100%

Terms modified by Central Memory

  • central memory cell
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    Selected Abstracts

    Multiple functions of human T cells generated by experimental malaria challenge

    EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 11 2009
    Stephen M. Todryk
    Abstract Protective immunity generated following malaria infection may be comprised of Ab or T cells against malaria Ag of different stages; however, the short-lived immunity that is observed suggests deficiency in immune memory or regulatory activity. In this study, cellular immune responses were investigated in individuals receiving Plasmodium falciparum sporozoite challenge by the natural (mosquito bite) route as part of a malaria vaccine efficacy trial. Parasitemia, monitored by blood film microscopy and PCR, was subsequently cleared with drugs. All individuals demonstrated stable IFN-,, IL-2 and IL-4 ex vivo ELISPOT effector responses against P. falciparum -infected RBC (iRBC) Ag, 28 and 90,days after challenge. However, infected RBC-specific central memory responses, as measured by IFN-, cultured ELISPOT, were low and unstable over time, despite CD4+ T cells being highly proliferative by CFSE dilution, and showed an inverse relationship to parasite density. In support of the observation of poor memory, co-culture experiments showed reduced responses to common recall Ag, indicating malaria-specific regulatory activity. This activity could not be accounted for by the expression of IL-10, TGF-,, FOXP3 or CTLA-4, but proliferating T cells expressed high levels of CD95, indicating a pro-apoptotic phenotype. Lastly, there was an inverse relationship between FOXP3 expression, when measured 10 days after challenge, and ex vivo IFN-, measured more than 100 days later. This study shows that malaria infection elicits specific Th1 and Th2 effector cells, but concomitant weak central memory and regulatory activity, which may help to explain the short-lived immunity observed. [source]

    Characterization of CC-chemokine receptor 7 expression on murine T cells in lymphoid tissues

    IMMUNOLOGY, Issue 2 2003
    Olle Bjorkdahl
    Summary Expression of the lymph node homing and CC-chemokine receptor 7 (CCR7), with L-selectin (CD62L), has been shown to divide human memory T cells into two functionally distinct subsets. We generated a polyclonal antibody against murine CCR7 and used this antibody to study CCR7 expression on murine T-cell subsets. Using flow cytometric staining of T cells for visualisation expression of CCR7 in association with CD62L and CD44, a major population of CD4 or CD8 T cells expressing CCR7 were found to be CD62Lhigh CD44low, which would suggest a naïve cell phenotype. By analogy with human studies, memory cells could be subdivided into CCR7high CD62Lhigh CD44high (central memory) and CCR7low CD62Llow CD44high (effector memory). The proportions of these populations were different in lymph node, blood and spleen. Functional, short-term in vitro polyclonal stimulation of blood, spleen and lymph node cells from naive mice demonstrated that CCR7high CD4 T cells produced predominantly interleukin (IL)-2, whereas CCR7low CD4 T cells produced both IL-2 and interferon-, (IFN-,). However, in contrast to previously published reports, the CCR7high CD8 T-cell subpopulation produced both IFN-, and IL-2. Analysis of effector T cells, induced by immunization in vivo, showed that a proportion of activated naïve CD4 T cells down-regulated CCR7 only after multiple cell divisions, and this coincided with the down-regulation of CD62L and production of IL-4 and IFN-,. Finally, analysis of effector T cells during the phase of maximal clonal expansion of secondary immune responses in vivo indicated that the vast majority of both IL-2- and IFN-,-producing cells are CCR7low, while few cytokine-expressing CCR7high T cells were detected. Our results support the hypothesis, developed from studies with human cells, that CCR7 may separate functionally different murine memory T-cell subpopulations, but indicate additional complexity in that CCR7high CD8 T cells also may produce IFN-,. [source]

    An early commitment to expression of a particular TCRV, chain on CD8+ T cells responding to attenuated Plasmodium berghei sporozoites is maintained following challenge with infectious sporozoites

    PARASITE IMMUNOLOGY, Issue 9-10 2010
    J. M. LUMSDEN
    Summary Protection induced by irradiated Plasmodium berghei sporozoites (Pb,-spz) in mice is linked to CD8+ T cells specific for exo-erythrocytic-stage Ags, and intrahepatic memory CD8+ T cells are associated with protracted protection. However, the Ag specificity of the protective CD8+ T cells remains largely unknown. In this study, we characterized the TCR V, usage by intrahepatic CD8+ T cells during ,-spz immunization and after the challenge with infectious Pb sporozoites. The repertoire of naïve (TN) and central memory (TCM) CD8+ T cells was diverse and conserved between individual mice, and did not change with immunization. In contrast, preferential usage of one or more TCR V, subset was observed in effector memory (TEM) CD8+ T cells after immunization. The expanded TCR V, varied between individual mice but V,4, 6, 7, 8.3, 9 and 11 were the most frequently expressed. In addition, there was a correlation in the TCR V, usage by ,-spz-induced CD8+ TEM in the liver and blood of individual mice. The expansion pattern of blood CD8+ TEM did not change with challenge and remained the same for 8 weeks thereafter. These results demonstrate that immunization with ,-spz skews the TCR V, repertoire of CD8+ TEM, and commitment to a particular TCR V, expression is maintained long-term. [source]

    Specific central nervous system recruitment of HLA-G+ regulatory T cells in multiple sclerosis,

    ANNALS OF NEUROLOGY, Issue 2 2009
    Yu-Hwa Huang MSci
    Objective We have recently described a novel population of natural regulatory T cells (Treg) that are characterized by the expression of HLA-G and may be found at sites of tissue inflammation (HLA-Gpos Treg). Here we studied the role of these cells in multiple sclerosis (MS), a prototypic autoimmune inflammatory disorder of the central nervous system (CNS). Methods Sixty-four patients with different types of MS, 9 patients with other neurological diseases, and 20 healthy donors were included in this study. Inflamed brain lesions from 5 additional untreated MS patients were examined. HLA-Gpos Treg were analyzed in the cerebrospinal fluid (CSF) by flow cytometry and in inflammatory demyelinating lesions of MS brain specimens by immunohistochemistry. Functional capacity was accessed and transmigration was determined using an in vitro model of the human blood-brain barrier (BBB). Results HLA-Gpos Treg were found enriched in the inflamed CSF of MS patients and in inflammatory demyelinating lesions of MS brain specimens. HLA-Gpos Treg showed a strong propensity to transmigrate across BBB, which was vigorously driven by inflammatory chemokines, and associated with a gain of suppressive capacity upon transmigration. CSF-derived HLA-Gpos Treg of MS patients represented a population of activated central memory activated T cells with an upregulated expression of inflammatory chemokine receptors and exhibiting full suppressive capacity. Unlike natural FoxP3-expressing Treg, HLA-Gpos Treg derived from peripheral blood were functionally unimpaired in MS. Interpretation In MS, HLA-Gpos Treg may serve to control potentially destructive immune responses directly at the sites of CNS inflammation and to counterbalance inflammation once specifically recruited to the CNS. Ann Neurol 2009 [source]

    FTY720 (fingolimod) in Multiple Sclerosis: therapeutic effects in the immune and the central nervous system

    BRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2009
    Volker Brinkmann
    FTY720 (fingolimod) is a first-in-class sphingosine 1-phosphate (S1P) receptor modulator that was highly effective in Phase II clinical trials for Multiple Sclerosis (MS). FTY720 is phosphorylated in vivo by sphingosine kinase-2 to form the active moiety FTY720-phosphate that binds to four of the five G protein-coupled S1P receptor subtypes. Studies using conditional S1P1 receptor-deficient and sphingosine kinase-deficient mice showed that the egress of lymphocytes from lymph nodes requires signalling of lymphocytic S1P1 receptors by the endogenous ligand S1P. The S1P mimetic FTY720-phosphate causes internalization and degradation of cell membrane-expressed S1P1, thereby antagonizing S1P action at the receptor. In models of human MS and demyelinating polyneuropathies, functional antagonism of lymphocytic S1P1 slows S1P-driven egress of lymphocytes from lymph nodes, thereby reducing the numbers of autoaggressive TH17 cells that recirculate via lymph and blood to the central nervous system and the sciatic/ischiatic nerves. Based on its lipophilic nature, FTY720 crosses the blood,brain barrier, and ongoing experiments suggest that the drug also down-modulates S1P1 in neural cells/astrocytes to reduce astrogliosis, a phenomenon associated with neurodegeneration in MS. This may help restore gap-junctional communication of astrocytes with neurons and cells of the blood,brain barrier. Additional effects may result from (down-) modulation of S1P3 in astrocytes and of S1P1 and S1P5 in oligodendrocytes. In conclusion, FTY720 may act through immune-based and central mechanisms to reduce inflammation and support structural restoration of the central nervous system parenchyma. Beyond the autoimmune indications, very recent studies suggest that short-term, low-dose administration of FTY720 could help treat chronic (viral) infections. Differential effects of the drug on the trafficking of naïve, central memory and effector memory T cell subsets are discussed. [source]