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Results for “Immunologic Memory”

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At least 1,549 records · Page 86Linked to original sources
PubMed1993

The fate of anergic T cells in vivo.

The kinetics of Staphylococcal enterotoxin B-(SEB) induced peripheral tolerance has been investigated. Ten days after SEB injection, thymectomized BALB/cByJ mice showed suppressed spleen cell proliferative responses to SEB. After 2 mo the SEB-specific response was partly recovered. Four months later the response of spleen cells of SEB-primed mice was comparable to those of control mice. The proportion of CD4+, V beta 8+ T cells was diminished in the tolerized mice and was not restored even after the response was recovered. Purified CD4+, V beta 8+ T cells from SEB-primed mice after 4 mo responded similarly to SEB as control CD4+, V beta 8+ T cells. These expressed a similar profile of surface markers compared with that of unprimed control cells, except a homing receptor was slightly lower. An experiment that addressed the possibility that non-anergic T cells expand over time and are in fact responsible for the recovery of the proliferative response showed that such events unlikely occur in vivo. Therefore, the data indicate that T cell anergy is reversible in vivo. It is also suggested that the challenge with superantigen results in neither clonal expansion nor specific CD4+, V beta 8+ T cell memory.

Animals↗
PubMed1996

IL-15 augments CD8+ T cell-mediated immunity against Toxoplasma gondii infection in mice.

Cytokines of the Th1 profile are important mediators of protective host immunity against Toxoplasma gondii infection in mice. In this study we describe the effect of the recently identified cytokine, IL-15, on prevention of murine infection with T. gondii. Administration of exogenous rIL-15 with soluble Toxoplasma lysate Ag (TLA) provides complete protection against a lethal parasite challenge, whereas treatment with either rIL-15 or TLA alone is not protective. Following immunization with TLA/rIL-15, there is a significant proliferation of splenocytes expressing the CD8+ phenotype in response to TLA. A significant rise in the level of serum IFN gamma was observed in vaccinated mice. Adoptive transfer of CD8+ T cells, but not CD4+ T cells, from TLA/rIL-15-vaccinated mice protects naive mice from a lethal parasite challenge. These CD8+ T cells exhibit enhanced CTL activity against target macrophages infected with T. gondii. Mice that have been immunized are protected against lethal parasite challenge for at least 1 mo postvaccination. These observations demonstrate that TLA when administered with exogenous rIL-15 generates toxoplasmacidal Ag-specific CD8+ T cells. These T cells proliferate upon exposure to parasite Ag, exhibit long term memory CTL against infected target cells, and may be involved in host immune memory to this parasite.

Adjuvants, Immunologic↗
PubMed2001

Epstein-Barr virus: exploiting the immune system.

In vitro, Epstein-Barr virus (EBV) will infect any resting B cell, driving it out of the resting state to become an activated proliferating lymphoblast. Paradoxically, EBV persists in vivo in a quiescent state in resting memory B cells that circulate in the peripheral blood. How does the virus get there, and with such specificity for the memory compartment? An explanation comes from the idea that two genes encoded by the virus--LMP1 and LMP2A--allow EBV to exploit the normal pathways of B-cell differentiation so that the EBV-infected B blast can become a resting memory cell.

B-Lymphocytes↗
PubMed2001

Autoreactivity, dynamic tuning and selectivity.

The immune system adjusts its response to the context in which antigens, including self-antigens, are recognized. Recent observations support a conceptual framework for understanding how this may be achieved at the cellular and cell-population levels. At both levels, 'perturbations' elicit competition between excitation and de-excitation, resulting either in adaptation or in various responses. The responsiveness of individual cells is dynamically tuned, reflecting their recent experience. The tuning of T-cell activation thresholds by self-ligands facilitates positive selection and continuously regulates the level of autoreactivity in the periphery. Autoreactivity appears to be involved in regulation of the immune response, homeostasis, maintaining of the functional integrity of naïve and memory cells, and in other physiological functions.

Adaptation, Physiological↗
PubMed2003

The immunological synapse for B-cell memory: the role of the ICOS and its ligand for the longevity of humoral immunity.

RECENT FINDINGS: The ICOS is one of the many costimulatory molecules of T cells. Recently, the authors discovered that the homozygous loss of the ICOS in humans presents as common variable immunodeficiency, the most prevalent treated primary immunodeficiency in man. Therefore, the ICOS is after CD40 and CD40-ligand deficiency the third costimulatory molecule for which a human disease has been described. PURPOSE OF REVIEW: The description of ICOS deficiency made it necessary to review the vast amount of knowledge from experimental models in the light of a new clinical immunodeficiency phenotype. To this end, after introducing the ICOS and its ligand and comparing the murine and human 'knockout', the role of the ICOS in parasitic and viral infections, asthma, autoimmunity, transplantation immunology, and tumor surveillance will be discussed. SUMMARY: The focus of this review is the interaction between the ICOS and its ligand, which is essential for T cell dependent B cell responses.

Animals↗
PubMed1995

Contributions of memory B cells to secondary immune response.

The secondary immune response is one of the most important features of immune systems. During the secondary immune response, the immune system can eliminate the antigen, which has been encountered by the individual during the primary invasion, more rapidly and efficiently. Both T and B memory cells contribute to the secondary response. In this paper, we only concentrate on the functions of memory B cells. We explore a model describing the memory contributed by the specific long-lived clone which is maintained by continued stimulation with a small amount of antigens sequestered on the surfaces of the follicular dendritic cells (FDC). The behavior of the secondary response provided by the model can be compared with experimental observations. The model shows that memory B cells indeed play an important role in the secondary response. It is found that a single memory cell in a long-lived clone may not be long-lived. In the present note, the influences of relevant parameters on the secondary response are also explored.

Animals↗
PubMed1994

Modeling HIV infection of CD4+ T-cell subpopulations.

We develop and analyze a set of models for the interaction of HIV with CD4+ T cells. We consider three major subpopulations of T cells: virgin, activated and memory. In our first model we assume that HIV can infect activated cells but not resting cells. We then generalize the model to take into account recent reports that HIV can enter resting cells but that such entry does not lead to the production of completely reverse transcribed copies of the viral genome or integration of the DNA copy into the host cell's genome unless cell activation occurs. Our models show that T-cell memory is greatly reduced by HIV infection and that T-cell depletion may be due to the direct killing of peripheral T cells and T-cell precursors in the thymus.

CD4-Positive T-Lymphocytes↗
PubMed1995

Lymphocyte memory and affinity selection.

The persistence of antigen-specific immune memory appears to require the presence of antigen--suggesting that memory may be due to restimulation of "memory" lymphocytes by persisting antigen. Persistence of antigen, in a form capable of stimulating B cell proliferation, on long-lived, follicular dendritic cells of lymphoid tissue is well documented. Existence of an analogous mechanism for T cell memory maintenance is controversial but can not be ruled out. Here we examine the consequences of immune memory maintenance by antigen-specific lymphocyte restimulation, and estimate the duration of memory as a function of model parameters. We show that the competition for restimulation among memory cell populations results in the selection of the clone having the highest overall affinity for the retained antigen. Thus affinity selection, an important attribute of immunity, is a constitutive property of memory maintenance by antigen-specific restimulation. In the case of B cells, affinity selection is predicted to continue to increase antibody affinity even after somatic mutation stops, and thus may be an important component of affinity maturation. Finally, we discuss several other hypotheses proposed to explain immune memory, including T cell stimulation by cross-reactive antigens.

Animals↗
PubMed1990

Human T-cell memory.

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Antibodies, Monoclonal↗
PubMed2004

The ageing of the blood supply and the lymphatic drainage of the skin.

The anatomy and functions of the blood and lymph vessels of human skin are described. Variation in these due to site, ageing and events during life consequent to exposure to a threatening environment are emphasised. Gradual atrophy and greater heterogeneity are features of ageing. Responses to injury and repair are complex and the interaction of mechanical signals distorting skin cells with numerous chemical signals are referred to. The lymphatics are part of an immunosurveillance system to monitor skin barrier penetration. The review attempts to draw attention to key recent advances in our understanding of the cytokine and growth factor production of the skin in the context of previous mainly physiological reviews especially influenced by 50 years of clinical practice as a dermatologist with an eye on both the skin and the fields of microcirculation and lymphology.

Adult↗