Cytolysis

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Cytolysis

An important immune function involving the dissolution of certain cells. There are a number of different cytolytic cells within the immune system that are capable of lysing a broad range of cells. The most thoroughly studied of these cells are the cytotoxic lymphocytes, which appear to be derived from different cell lineages and may employ a variety of lytic mechanisms. Cytotoxic cells are believed to be essential for the elimination of oncogenically or virally altered cells, but they can also play a detrimental role by mediating graft rejection or autoimmune disease. There are two issues regarding cytotoxic lymphocytes that are of concern: one is the target structure that is being recognized on the target cell, that is, the cell that is killed, which triggers the response; and the other is the lytic mechanism. See Cellular immunology

When freshly isolated, large granular lymphocytes from peripheral blood are tested in cytotoxicity assays, they spontaneously lyse certain tumor cells. These cytotoxic cells are called natural killer cells, and they are important mediators of innate immunity as a first line of defense against invading pathogens. They are unique in that no previous sensitization is required for them to kill. It now appears that a number of different receptors on natural killer cells are capable of activating the lytic machinery. Recently, it has been found that these cells also express inhibitory receptors that actually inhibit cell lysis, thus adding another level of complexity to the regulation of cytolysis by these cells.

Another killer cell, called the lymphokine-activated killer cell can lyse any target cell, including cells from freshly isolated tumors, and are employed in cancer therapy. Lymphokine-activated killer cells may also be important in mounting a vigorous response under conditions of extreme immunological stress. Very little is known about the mechanisms by which these cells recognize and lyse the target cell.

The last group of cytotoxic cells is the cytotoxic T lymphocyte. These are T cells that can lyse any target cell in an antigen-specific fashion. That is, as a population they are capable of lysing a wide range of target cells, but an individual cytotoxic T lymphocyte is capable of lysing only those target cells which bear the appropriate antigen. These are truly immune cells in that they require prior sensitization in order to function. These cells are thought to mediate graft rejection, mount responses against viral infections and intracellular bacterial infections, and play a major role in tumor destruction.

Cytotoxic cell-mediated lysis is divided into three distinct steps. The first step is conjugation, when the killer cell determines if the target cell expresses the appropriate antigen and binds to it via a complex array of adhesion molecules. The second step involves the programming for lysis in which the lytic event is triggered. The third step is the destruction of the target cell.

Direct cell contact between the target cell and the killer cell is absolutely required for initiating the lytic mechanism. Killer cells remain unscathed during the lytic event, suggesting that the killer cell must either employ a unidirectional lytic mechanism or be resistant to the lytic mechanism. Also, when many, but not all, target cells die after cytotoxic T-lymphocyte interaction, nuclear damage with rapid DNA fragmentation precedes detectable plasma membrane damage. See Antigen, Histocompatibility

It is becoming clear that cytotoxic lymphocytes employ multiple mechanisms designed to initiate target cell destruction. If cytolysis exists to protect the organism from invading pathogens, there should be redundancies in the system so that, if the pathogen has a mechanism for escaping one cytolytic pathway, alternative mechanisms would still be functional. Two mechanisms are the degranulation of cytolytic granules and the triggering of death receptors found on target cells. In the degranulation mechanism of killing, cytotoxic cells release the contents of cytotoxic granules after specific interaction with the target cell. This results in the leakage of salts, nucleotides, and proteins from the target cell, leading to cell death.

On virtually all cells of the body a number of receptors have been identified that are able to trigger apoptosis when engaged. These receptors are called death receptors. The most studied, and relevant to cytolytic cells, is a receptor called Fas. Fas, when engaged by its ligand (FasL), triggers the caspase cascade leading to the hallmark signs of apoptosis, which include membrane blebbing, chromosomal condensation, nuclear disintegration, DNA fragmentation, and cell death.

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Cytolysis

 

the destruction of animal and plant cells by complete or partial dissolution. Lysosomes, which are intracellular structures, play an active part in cytolysis. They contain enzymes that split the high-molecular-weight components of the cell, such as proteins, nucleic acids, polysaccharides, and lipids. Cytolysis occurs under normal physiological conditions, as in metamorphosis, and in a variety of pathological states. (For additional information, seeLYSOSOMES and .)

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

cytolysis

[sī′täl·ə·səs]
(pathology)
Disintegration or dissolution of cells, usually associated with a pathologic process.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Jha, "CD4+ CD28null cells are expanded and exhibit a cytolytic profile in end-stage renal disease patients on peritoneal dialysis," Nephrology Dialysis Transplantation, vol.
A MAGE-A3 peptide presented by HLA-DP4 is recognized on tumor cells by [CD4.sup.+] cytolytic T lymphocytes.
This cytolytic activity is modulated by a second plasma protein, [[Alpha].sub.2]-macroglobulin, and that activity appears to depend on the generation of a new free thiol group when [[Alpha].sub.2]-macroglobulin is activated by its reaction with proteases.
However, previous data suggest that the phosphatidylcholine-specific phospholipase C (PC-PLC) enzyme could play an important role in regulating the CD16 membrane expression, the CD16-mediated cytolytic mechanism, and the CD16-triggered signal transduction in NK cells.
van der Bruggen, "A MAGE-A4 peptide presented by HLA-A2 is recognized by cytolytic T lymphocytes," European Journal of Immunology, vol.
Falco et al., "The analysis of the natural killer-like activity of human cytolytic T lymphocytes revealed HLA-E as a novel target for TCR alpha/beta-mediated recognition," European Journal of Immunology, vol.
In vivo, robust cytolytic function towards mKRAS-presenting targets can be measured in the T-cells generated through the AMP vaccination regimen.
On July 8, 2019, we announced the publication of a study in BMC Biotechnology, a Springer Nature journal, which described and evaluated the development of the SWIFF-CAR, a CAR construct with an embedded on/off-switch, which enables tight control of the CAR surface presentation and subsequent cytolytic functions using a small molecule drug.
Cellectis announced the publication of a study in BMC Biotechnology, a Springer Nature journal, describing and evaluating the development of the SWIFF-CAR, a CAR construct with an embedded on/off-switch, which enables tight control of the CAR surface presentation and subsequent cytolytic functions using a small molecule drug.
Further macrophages are activated and along with iNOS and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, act to kill the invading bacteria.10 NK cells act at the site of infection to increase IFN-g production and lysis of Mtb infected cells.11 They modulate T cells in favour of the Th1 response, thereby enabling the host to fight off the invading infection through CD8+ T cell-derived IFN-g production and cytolytic activity.12 Dendritic cells act at the site of infection in order to uptake the bacteria and process, and upon maturation, present the antigens.
Bacterial two-component and hetero-heptameric pore-forming cytolytic toxins: structures, pore-forming mechanism, and organization of the genes.