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Results for “Immunologic Memory”

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At least 1,675 records · Page 93Linked to original sources
PubMed1976

Secondary cytotoxic allograft responses in vitro. II. Differentiation of memory T cells into cytotoxic T lymphocytes in the absence of cell proliferation.

Murine cytotoxic T lymphocytes (CTL) were induced in "one-way" mixed lymphocyte cultures and their physical characteristics investigated by velocity sedimentation at 1 X g. The in vitro differentiation of progenitors of CTL into primary and secondary CTL was paralleled by characteristic changes in the size of the responder cells. Fractionated cells enriched for primary blast CTL reverted into clonally restricted "nonlytic" secondary T lymphocytes. Upon antigenic reexposure, these lymphocytes differentiated into secondary CTL within 18-32 h. This took place in the absence of cell proliferation and could be triggered by UV light irradiated allogeneic stimulator cells. It is suggested the different characteristics for the induction of either a primary or secondary cytotoxic T cell response reflect qualitative differences between unprimed T cells and memory T lymphocytes.

Animals↗
PubMed1993

Do the CD45RO+CD8+ intestinal intraepithelial T lymphocytes have the characteristics of memory cells?

Human intraepithelial lymphocytes (IEL) are predominantly CD45RO+ (memory) CD8+ T lymphocytes located between intestinal epithelial cells. This study determines whether IEL share other characteristics with circulating CD45RO+ lymphocytes. Memory cells are large and have an upregulated expression of adhesion molecules. In contrast, the majority of IEL are the same size as peripheral blood (PB) T cells. In addition, IEL do not have an increased density of adhesion molecules, although a larger percentage express CD54 and CD58 compared to PBL. Allo-CTL activity, demonstrated by CD45RO+ PBL, could not be shown using either IEL or lamina propria lymphocytes (LPL) after a 5-day culture with alloantigen. However, after a 2.5-week culture with allogeneic PBL and interleukin-2 (IL-2), both IEL and LPL were capable of this cytotoxic function. The addition of IL-4 or IL-6 did not alter CTL activity by mucosal lymphocytes. Alloantigen-stimulated IEL, LPL, and PB CD8+ T cell lines were propagated for up to 16 weeks. All lines demonstrated alloantigen-specific proliferation. The PB CD8+ T lymphocytes maintained their phenotype and allo-CTL activity. In contrast, the CD4+ subset in the IEL and LPL became the predominant lymphocyte type and demonstrated potent lytic activity that was not alloantigen specific. This study shows that (1) IEL do not have increased density of adhesion molecules, (2) mucosal lymphocytes demonstrate allo-CTL activity, (3) CD8+ T cells in the mucosa cannot be perpetuated long-term by alloantigen and IL-2, and (4) mucosal CD4+ T cell lines demonstrate marked alloantigen-nonspecific cytotoxicity. The only characteristic shared by IEL and circulating memory cells is allo-CTL activity.

CD8 Antigens↗
PubMed1995

Germinal center T cells exhibit properties of memory helper T cells.

Potential roles of germinal center (GC) T cells in immune memory were investigated by examining T cells in GCs lymph nodes (LNs) following immunization with myelin basic protein (MBP). MBP preferentially stimulates T cells expressing the V beta 8 TCR family in B10.PL mice. By staining lymph nodes with peanut agglutinin, GCs were first identified 8 days after immunization and could still be detected 50 days later. When T cells within GCs were examined at Day 8, the majority (> 90%) were CD45RB-negative and a large percentage (20%) had already proliferated several days before as determined by bromodeoxyuridine (BrdU) incorporation. When BrdU+ V beta 8+ cells were examined in various areas of LNs 3 and 8 weeks after immunization, BrdU+ V beta 8+ cells were approximately fourfold more frequent in GCs than other areas of LNs. When GCs were examined for IL-4 mRNA+ cells using an in situ hybridization method, only 0.01% of GC cells expressed IL-4 mRNA, corresponding to about 1% of GC T cells. Shortly following restimulation with MBP, the frequency of cells expressing IL-4 mRNA increased fivefold. Taken together, these findings indicate that GC T cells possess characteristics associated with memory T cells.

Animals↗
PubMed1988

The kinetics of generation of influenza-specific cytotoxic T-lymphocyte precursor cells.

A dramatic increase in the number of restimulatable (memory) cytolytic T-cell precursors (CTLps) has been demonstrated to occur 2 to 4 days postimmunization. By 4 or at the latest 6 days following in vivo priming, the frequency of restimulatable influenza-specific CTLps has reached that characteristic of a memory response. This indicates that the proliferative events which give rise to memory CTLps occur earlier than might have been expected and in fact are completed prior to the cessation of othe primary CTL response. Such information may have important significance to future immunomodulatory efforts aimed at perturbing the establishment of T-cell memory in vivo.

Animals↗
PubMed2005

Understanding the generation and function of memory T cell subsets.

Memory T cells can be broadly divided into central memory and effector memory subsets, which are endowed with different capacities to home to lymphoid or non-lymphoid tissues, to proliferate in response to antigen or cytokines and to perform effector functions. In the past few years progress has been made in understanding the properties of these memory T cell subsets and, in particular, the signals required for their generation and maintenance. Collectively these data point to a critical role of central memory T cells in conferring long-term immunity.

Cell Differentiation↗
PubMed1996

Viral immunity: interferons jog old T-cell memories.

The mechanism by which life-long immunity to viruses persists is a matter of some controversy. Interferons induced by subsequent unrelated viral infections may propagate existing memory T cells non-specifically.

Animals↗