Regular ArticleDNA Fragmentation Induced by Cytotoxic T Lymphocytes Can Result in Target Cell Death
Abstract
Cytotoxic T lymphocyte (CTL)-mediated lysis is accompanied by fragmentation of target cell DNA into an oligonucleosome ladder, a hallmark of apoptosis. Is this a fortuitous coincidence, or could CTL be inducing lysis by activation of the suicide signal? In this report we demonstrate that CTL-mediated target cell death can be blocked with the drug aurintricarboxylic acid (ATA). The abrogation of death correlates with the inhibition of DNA fragmentation. While ATA prevented DNA fragmentation, it failed to significantly alter protein, RNA, or DNA synthesis in the cell lines over the dose range used. In addition, there was no inhibition of cell-cell interaction or granule exocytosis during CTL-mediated killing. ATA also significantly inhibited the cytolysis and DNA fragmentation mediated by isolated cytolytic granules, as well as the granular protein fragmentin. We developed an assay in which target cells could be separated from CTL after binding and programming for lysis. Once they had received the "kiss of death," target cells could be rescued from lysis (as indicated by inhibition of DNA fragmentation and increased target cell viability) by treatment with ATA. These results suggest that ATA blocks target cell death by inhibition of DNA fragmentation, and further, that chromatin degradation is a cause rather than a result of cell death in CTL-mediated lysis.
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Adaptive or antigen-specific immune response
2009, MedicineRisk for influenza increases with age while cellular immune responses decline. This was a prospective study to determine the relationship between cytokine and granzyme B levels in peripheral blood mononuclear cells stimulated with live influenza virus, and subsequent influenza illness. Granzyme B levels were lower in the group who later developed symptomatic laboratory-confirmed influenza (n=10) compared to the group who did not (n=90) (ANOVA, P=0.024). In contrast, none of the cytokine levels were related to the development of influenza. Thus, granzyme B is a potential marker of influenza risk in older adults.
Apoptosis in a canine model of acute chagasic myocarditis
1999, Journal of Molecular and Cellular CardiologyHistologic, ultrastructural and nick end labeling studies were made to evalute the occurrence of apoptosis in the hearts of dogs with acute myocarditis due to experimental infection withT. cruzi. The best results for the detection of apoptosis by nick end labeling were obtained by a method combining the use of terminal deoxynucleotidyl transferase, CoCl2and fluorescein-conjugated deoxyuridine triphosphate, followed by counterstaining of DNA with 4′6-diamidino-2-phenylindole (DAPI) and examination by laser scanning confocal fluorescence microscopy. Apoptosis was found in: (1) cardiac myocytes; (2) endothelial cells of capillaries and venules; (3) immune effector cells, including macrophages, interstitial dendritic cells (antigen-presenting cells) and granular and agranular lymphocytes, and (4) intra- and extracellular forms ofT. cruzi. The apoptosis in myocytes and endothelial cells affected cells that were not infected byT. cruziand was probably caused by the release of toxic mediators of inflammation. The apoptosis of immune effector cells could be related either to the subsidence of inflammation or to modulation (and even failure) of the immune response. The finding of apoptosis inT. cruziconfirms the results of other studies showing that this phenomenon occurs during the differentiation of trypomastigotesin vitro. Thus, apoptosis constitutes an important and multifactorial event in the pathogenesis of acute Chagasic myocarditis.
Death and Dying in the Immune System
1997, Advances in PharmacologyThe phenomenon of physiological cell death involves the transformation of healthy cells to condensed apoptotic bodies. The dead cell corpse, with its characteristic morphology, is the end point of the process. The discussion presented in this chapter is an assumption that the hallmarks of this process reveal a common mechanism of dying. Issues of death (especially in the contexts of cell turnover and negative selection) have long been appreciated as central to immunobiology. As a result, physiological cell death has been extensively studied in lymphocytes. Although selective physiological death occurs among cells generally during ontogeny, lymphocytes are unusual in retaining susceptibility to a large variety of suicide inducers throughout their life cycle. The selective induction of physiological cell death in lymphocytes serves two distinct functions. The first, of course, is in central repertoire selection-in the initial and early elimination of functionally inappropriate clonal populations. The second and equally critical role of physiological cell death is in the dampening of immune responses. As demonstrated in studies of activation-driven cell death, the response of a lymphocyte to an antigenic stimulus is finite. A lymphocyte may exert effector function and proliferate in response to antigen, but by virtue of that response the cell is made susceptible to death upon further stimulation.
A physical interaction between the cell death protein fas and the tyrosine kinase p59<sup>fynT</sup>
1996, Journal of Biological ChemistryThe Fas antigen (Apo1/CD95) is a transmembrane protein belonging to the nerve growth factor receptor family. It is expressed on a variety of cells, including activated T lymphocytes. Ligation of Fas with its natural ligand or with anti-Fas antibodies often results in the apoptotic death of the cell, making Fas an important mediator of down-regulating immune responses. The signal transduction pathways utilized by Fas are currently unknown, although tyrosine kinase activity has recently been strongly implicated. Here, we report that the tyrosine kinase p59fyn physically associates with Fas in Fas-sensitive cells. In addition, we show that activated T lymphocytes from fyn knockout mice exhibit elevated lifespans and reduced apoptosis in vitro compared to their normal counterparts. Furthermore, activated T lymphocytes from the fyn- deficient mice are less sensitive to killing by both anti-Fas antibody and Fas-ligand cytotoxic T cells. These results suggest that p59fyn plays an important role in Fas signal transduction.
Apoptosis - Molecular mechanisms and biomedical implications
1996, Molecular Aspects of MedicineApoptosis is a distinct form of cell death of importance in tissue development and homeostasis and in several diseases. This review summarizes current knowledge about the regulation and molecular mechanisms of apoptosis and discusses the potential role of disregulated apoptosis in several major diseases. Finally, we speculate that modulation of apoptosis may be a target in future drug therapy.