scholarly journals Increased Thymic Output during Acute Measles Virus Infection

2003 ◽  
Vol 77 (14) ◽  
pp. 7872-7879 ◽  
Author(s):  
Sallie R. Permar ◽  
William J. Moss ◽  
Judith J. Ryon ◽  
Daniel C. Douek ◽  
Mwaka Monze ◽  
...  
Keyword(s):  
T Cells ◽  
T Lymphocytes ◽  
Hospital Discharge ◽  
Measles Virus ◽  
Cell Receptor ◽  
Cell Mediated Immunity ◽  
Healthy Children ◽  
Thymic Output ◽  
Interleukin 7

ABSTRACT Measles virus infects thymic epithelia, induces a transient lymphopenia, and impairs cell-mediated immunity, but thymic function during measles has not been well characterized. Thirty Zambian children hospitalized with measles were studied at entry, hospital discharge, and at 1-month follow-up and compared to 17 healthy children. During hospitalization, percentages of naïve (CD62L+, CD45RA+) CD4+ and CD8+ T lymphocytes decreased (P = 0.01 for both), and activated (HLA-DR+, CD25+, or CD69+) CD4+ and CD8+ T lymphocytes increased (P = 0.02 and 0.03, respectively). T-cell receptor rearrangement excision circles (TRECs) in measles patients were increased in CD8+ T cells at entry compared to levels at hospital discharge (P = 0.02) and follow-up (P = 0.04). In CD4+ T cells, the increase in TRECS occurred later but was more sustained. At discharge, TRECs in CD4+ T cells (P = 0.05) and circulating levels of interleukin-7 (P = 0.007) were increased compared to control values and remained elevated for 1 month, similar to observations in two measles virus-infected rhesus monkeys. These findings suggest that a decrease in thymic output is not the cause of the lymphopenia and depressed cellular immunity associated with measles.

scholarly journals CD27 Expression Promotes Long-Term Survival of Functional Effector–Memory CD8+Cytotoxic T Lymphocytes in HIV-infected Patients

2004 ◽  
Vol 200 (11) ◽  
pp. 1407-1417 ◽  
Author(s):  
Adrian F. Ochsenbein ◽  
Stanley R. Riddell ◽  
Michele Brown ◽  
Lawrence Corey ◽  
Gabriela M. Baerlocher ◽  
...  
Keyword(s):  
T Cells ◽  
T Lymphocytes ◽  
Cytotoxic T Lymphocytes ◽  
Cd8 T Cells ◽  
Interleukin 2 ◽  
Tumor Necrosis Factor Receptor ◽  
Cell Receptor ◽  
Effector Memory ◽  
Term Survival ◽  
Functional Consequences

Human immunodeficiency virus (HIV)-specific CD8+ T cells persist in high frequencies in HIV-infected patients despite impaired CD4+ T helper response to the virus, but, unlike other differentiated effector cytotoxic T lymphocytes, most continue to express the tumor necrosis factor receptor family member CD27. Because the ligand for CD27 (CD70) is also overexpressed in HIV-infected hosts, we examined the nature of expression and potential functional consequences of CD27 expression on HIV-specific CD8+ T cells. Analysis of CD27+ and CD27− T cells derived from the same HIV-specific clone revealed that retention of CD27 did not interfere with acquisition of effector functions, and that after T cell receptor stimulation, CD27+ cells that concurrently were triggered via CD27 exhibited more resistance to apoptosis, interleukin 2 production, and proliferation than CD27− T cells. After transfer back into an HIV-infected patient, autologous HIV-specific CD27− T cells rapidly disappeared, but CD27+ T cells derived from the same clone persisted at high frequency. Our findings suggest that the CD27–CD70 interaction in HIV infection may provide CD27+ CD8+ T cells with a survival advantage and compensate for limiting or absent CD4+ T help to maintain the CD8 response.

scholarly journals Small amounts of superantigen, when presented on dendritic cells, are sufficient to initiate T cell responses.

1993 ◽  
Vol 178 (2) ◽  
pp. 633-642 ◽  
Author(s):  
N Bhardwaj ◽  
J W Young ◽  
A J Nisanian ◽  
J Baggers ◽  
R M Steinman
Keyword(s):  
T Cells ◽  
Dendritic Cells ◽  
T Cell ◽  
Dendritic Cell ◽  
Mhc Class Ii ◽  
Cell Receptor ◽  
Class Ii ◽  
Cell Mediated Immunity ◽  
Quiescent T Cells ◽  
Antigen Presenting

Dendritic cells are potent antigen-presenting cells for several primary immune responses and therefore provide an opportunity for evaluating the amounts of cell-associated antigens that are required for inducing T cell-mediated immunity. Because dendritic cells express very high levels of major histocompatibility complex (MHC) class II products, it has been assumed that high levels of ligands bound to MHC products ("signal one") are needed to stimulate quiescent T cells. Here we describe quantitative aspects underlying the stimulation of human blood T cells by a bacterial superantigen, staphylococcal enterotoxin A (SEA). The advantages of superantigens for quantitative studies of signal one are that these ligands: (a) engage MHC class II and the T cell receptor but do not require processing; (b) are efficiently presented to large numbers of quiescent T cells; and (c) can be pulsed onto dendritic cells before their application to T cells. Thus one can relate amounts of dendritic cell-associated SEA to subsequent lymphocyte stimulation. Using radioiodinated SEA, we noted that dendritic cells can bind 30-200 times more superantigen than B cells and monocytes. Nevertheless, this high SEA binding does not underlie the strong potency of dendritic cells to present antigen to T cells. Dendritic cells can sensitize quiescent T cells, isolated using monoclonals to appropriate CD45R epitopes, after a pulse of SEA that occupies a maximum of 0.1% of surface MHC class II molecules. This corresponds to an average of 2,000 molecules per dendritic cell. At these low doses of bound SEA, monoclonal antibodies to CD3, CD4, and CD28 almost completely block T cell proliferation. In addition to suggesting new roles for MHC class II on dendritic cells, especially the capture and retention of ligands at low external concentrations, the data reveal that primary T cells can generate a response to exceptionally low levels of signal one as long as these are delivered on dendritic cells.

scholarly journals SLFN2 protection of tRNAs from stress-induced cleavage is essential for T cell–mediated immunity

Science ◽  
2021 ◽  
Vol 372 (6543) ◽  
pp. eaba4220 ◽  
Author(s):  
Tao Yue ◽  
Xiaoming Zhan ◽  
Duanwu Zhang ◽  
Ruchi Jain ◽  
Kuan-wen Wang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Interleukin 2 ◽  
Cell Receptor ◽  
Cell Mediated Immunity ◽  
Activated T Cells ◽  
Granule Formation

Reactive oxygen species (ROS) increase in activated T cells because of metabolic activity induced to support T cell proliferation and differentiation. We show that these ROS trigger an oxidative stress response that leads to translation repression. This response is countered by Schlafen 2 (SLFN2), which directly binds transfer RNAs (tRNAs) to protect them from cleavage by the ribonuclease angiogenin. T cell–specific SLFN2 deficiency results in the accumulation of tRNA fragments, which inhibit translation and promote stress-granule formation. Interleukin-2 receptor β (IL-2Rβ) and IL-2Rγ fail to be translationally up-regulated after T cell receptor stimulation, rendering SLFN2-deficient T cells insensitive to interleukin-2’s mitogenic effects. SLFN2 confers resistance against the ROS-mediated translation-inhibitory effects of oxidative stress normally induced by T cell activation, permitting the robust protein synthesis necessary for T cell expansion and immunity.

scholarly journals Circulating CD8 T Lymphocytes in Human Immunodeficiency Virus-Infected Individuals Have Impaired Function and Downmodulate CD3ζ, the Signaling Chain of the T-Cell Receptor Complex

Blood ◽  
1998 ◽  
Vol 91 (2) ◽  
pp. 585-594 ◽  
Author(s):  
Linda A. Trimble ◽  
Judy Lieberman
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
T Cell ◽  
T Lymphocytes ◽  
T Cell Receptor ◽  
Cell Receptor ◽  
Receptor Complex ◽  
Cd8 T Lymphocytes ◽  
Immunodeficiency Virus ◽  
Specific Cytotoxicity

Although human immunodeficiency virus (HIV)-infected subjects without acquired immunodeficiency syndrome have a high frequency of HIV-specific CD8 T lymphocytes, freshly isolated lymphocytes frequently lack detectable HIV-specific cytotoxicity. However, this effector function becomes readily apparent after overnight culture. To investigate reasons for T-cell dysfunction, we analyzed T-cell expression of the cytolytic protease granzyme A and of CD3ζ, the signaling component of the T-cell receptor complex. An increased proportion of CD4 and CD8 T cells from HIV-infected donors contain granzyme A, consistent with the known increased frequency of activated T cells. In 28 HIV-infected donors with mild to advanced immunodeficiency, a substantial fraction of circulating T cells downmodulated CD3ζ (fraction of T cells expressing CD3ζ, 0.74 ± 0.16 v 1.01 ± 0.07 in healthy donors; P < .0000005). CD3ζ expression is downregulated more severely in CD8 than CD4 T cells, decreases early in infection, and correlates with declining CD4 counts and disease stage. CD3ζ expression increases over 6 to 16 hours of culture in an interleukin-2–dependent manner, coincident with restoration of viral-specific cytotoxicity. Impaired T-cell receptor signaling may help explain why HIV-specific cytotoxic T lymphocytes fail to control HIV replication.

scholarly journals Modulation of let-7 miRNAs controls the differentiation of effector CD8 T cells

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Alexandria C Wells ◽  
Keith A Daniels ◽  
Constance C Angelou ◽  
Eric Fagerberg ◽  
Amy S Burnside ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Lymphocytes ◽  
Cytotoxic T Lymphocytes ◽  
Cd8 T Cells ◽  
T Cell Responses ◽  
Cd8 T Cell ◽  
Cell Receptor ◽  
Activated T Cells ◽  
Cell Responses

The differentiation of naive CD8 T cells into effector cytotoxic T lymphocytes upon antigen stimulation is necessary for successful antiviral, and antitumor immune responses. Here, using a mouse model, we describe a dual role for the let-7 microRNAs in the regulation of CD8 T cell responses, where maintenance of the naive phenotype in CD8 T cells requires high levels of let-7 expression, while generation of cytotoxic T lymphocytes depends upon T cell receptor-mediated let-7 downregulation. Decrease of let-7 expression in activated T cells enhances clonal expansion and the acquisition of effector function through derepression of the let-7 targets, including Myc and Eomesodermin. Ultimately, we have identified a novel let-7-mediated mechanism, which acts as a molecular brake controlling the magnitude of CD8 T cell responses.

scholarly journals Modalities of Interleukin-7-Induced Human Immunodeficiency Virus Permissiveness in Quiescent T Lymphocytes

2002 ◽  
Vol 76 (18) ◽  
pp. 9103-9111 ◽  
Author(s):  
Odile Ducrey-Rundquist ◽  
Mireille Guyader ◽  
Didier Trono
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
T Cells ◽  
T Lymphocytes ◽  
T Cell Homeostasis ◽  
Activated T Cells ◽  
Hiv Susceptibility ◽  
Interleukin 7 ◽  
Immunodeficiency Virus ◽  
Cell Cycle Status

ABSTRACT The metabolic and cell cycle status of primary T lymphocytes conditions their susceptibility to human immunodeficiency virus (HIV) and HIV-derived vectors. While in fully quiescent T lymphocytes the reverse transcription and nuclear import of these retroelements are impaired, leading to an abortive infection, various stimuli can induce a state of virus permissiveness. Here, we studied the modalities by which interleukin-7 (IL-7), an important controller of T-cell homeostasis, exerts this effect. IL-7-exposed cord blood T lymphocytes proliferated and were efficiently transduced by HIV-derived vectors. In contrast, similarly treated adult peripheral blood (PB) T lymphocytes failed to divide, and only a subset of these cells became infectible. HIV-resistant and -sensitive subsets of IL-7-treated PB T lymphocytes differed in cell cycle status but not in naïve, memory, or activation phenotypes. Nuclear factor of activated T cells was not induced by IL-7, and cyclosporine did not prevent HIV-mediated gene transfer. Furthermore, the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin blocked IL-7-induced cell survival and Bcl-2 synthesis but had no effect on the acquisition of HIV susceptibility, suggesting that IL-7-induced HIV type 1 permissiveness is not mediated by the PI-3 K pathway and that, perhaps, the Jak/STAT5 pathway, the other known mediator of IL-7-triggered signaling in T cells, governs this process.

scholarly journals Interleukin-7 Enhances Proliferation Responses to T-Cell Receptor Stimulation in Naïve CD4+ T Cells from Human Immunodeficiency Virus-Infected Persons

2007 ◽  
Vol 81 (22) ◽  
pp. 12670-12674 ◽  
Author(s):  
Douglas A. Bazdar ◽  
Scott F. Sieg
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
T Cell ◽  
T Cell Receptor ◽  
Cell Receptor ◽  
Healthy Controls ◽  
Receptor Stimulation ◽  
Interleukin 7 ◽  
Immunodeficiency Virus ◽  
Antigen Presenting

ABSTRACT Proliferation responses of naïve CD4+ T cells to T-cell receptor and interleukin-7 (IL-7) stimulation were evaluated by using cells from human immunodeficiency virus-positive (HIV+) donors. IL-7 enhanced responses to T-cell receptor stimulation, and the magnitude of this enhancement was similar in cells from healthy controls and from HIV+ subjects. The overall response to T-cell receptor stimulation alone or in combination with IL-7, however, was diminished among viremic HIV+ donors and occurred independent of antigen-presenting cells. Frequencies of CD127+ cells were related to the magnitudes of proliferation enhancement that were mediated by IL-7. Thus, IL-7 enhances but does not fully restore the function of naïve CD4+ T cells from HIV-infected persons.

scholarly journals Priming of T cells to Fas-mediated proliferative signals by interleukin-7

Blood ◽  
2008 ◽  
Vol 112 (4) ◽  
pp. 1195-1204 ◽  
Author(s):  
Bence Rethi ◽  
Nancy Vivar ◽  
Stefano Sammicheli ◽  
Caroline Fluur ◽  
Nicolas Ruffin ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Lymphocyte ◽  
Cell Receptor ◽  
Cell Depletion ◽  
Activated T Cells ◽  
T Cell Depletion ◽  
Interleukin 7 ◽  
Costimulatory Signals ◽  
Opposing Effects

Abstract T-cell depletion associated with HIV infection or cytoreductive therapies triggers potential T-cell regenerative mechanisms such as peripheral T-lymphocyte expansion to weak antigenic stimuli and the increased availability of interleukin-7 (IL-7), a cytokine with potent antiapoptotic and proliferative activities. Deleterious mechanisms also associated with lymphopenia, such as increased Fas expression and apoptosis of T cell, however, may result in opposing effects. In this study, we show that Fas molecules, primarily associated with T-cell depletion in lymphopenic settings, may also contribute to compensatory T-cell expansion through transmitting costimulatory signals to suboptimally activated T cells. Proliferation of T lymphocytes in response to concomitant Fas and T-cell receptor (TCR) triggering was shown to be increased in HIV-infected individuals compared with noninfected controls. As IL-7 levels are often elevated in lymphopenic individuals in association with increased Fas expression, we analyzed whether IL-7 would influence Fas-mediated proliferative signals in T cells. We show that IL-7 is able to increase the efficacy of Fas to induce proliferation of suboptimally activated T cells. Thus, high IL-7 levels associated with lymphopenic conditions may simultaneously induce sensitivity to Fas-mediated apoptosis in nonactivated T cells and increase Fas-induced costimulatory signals in T cells recognizing low-affinity antigens.

scholarly journals Cd8 Expression up to the Double-Positive CD3Low/Intermediate Stage of Thymic Differentiation Is Sufficient for Development of Peripheral Functional Cytotoxic T Lymphocytes

2001 ◽  
Vol 194 (5) ◽  
pp. 685-694 ◽  
Author(s):  
X.-L. Zhang ◽  
S. Zhao ◽  
S.H. Borenstein ◽  
Y. Liu ◽  
B. Jayabalasingham ◽  
...  
Keyword(s):  
T Cells ◽  
T Lymphocytes ◽  
Cytotoxic T Lymphocytes ◽  
Intermediate Stage ◽  
Cell Receptor ◽  
Double Positive ◽  
Cis Acting ◽  
Functional Studies ◽  
Peripheral T Cells

Control of CD8α transcription during development of α/β T cell receptor (TCR) T lymphocytes is mediated by at least two distinct stage-specific cis-acting transcriptional mechanisms (i.e., enhancers). On the CD8α−/−knockout (KO) background, cis-mechanism I and cis-mechanism II together mediate appropriate stage- and sublineage-specific transgenic (Tg) CD8α expression and “rescue” development of peripheral CD8+ single-positive (SP) cytotoxic T lymphocytes (CTLs). In contrast, on the wild-type (WT)/CD8+/+ or CD8α−/−KO backgrounds, a CD8α Tg directed by cis-mechanism I alone is activated during the double negative [DN] to double positive [DP] transition and expressed up to the CD3low/intermediate DP stage but not in more mature DP or SP thymocytes or peripheral T cells. As loss of cis mechanism I activity occurs around the onset of positive selection, it is possible that events associated with TCR/major histocompatibility complex (MHC) interactions and selection are involved in initiating these changes in CD8α transcription. To examine this issue, phenotypic and functional studies were performed for thymocytes and T cells of CD8α−/−KO mice that expressed a CD8α Tg under control of cis-mechanism I only. Despite loss of CD8α expression at the DP CD3low/intermediate stage, increased populations of mature CD3hiCD4−CD8− thymocytes and CD3+CD4−CD8− peripheral T cells were detected. By several criteria, including MHC class I–restricted antigen recognition, these cells have at least partially undergone positive and negative selection. Therefore, initiation of selection and sublineage commitment are determined before loss of cis-mechanism I–mediated control of CD8α transcription. Further, CD8 expression beyond the CD3low/intermediate DP thymic stage is not essential for CTL development in vivo or function.

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