Which cells destroy body cells infected by viruses

Ligation of the T-cell receptor similarly induces de novo synthesis of perforin and granzymes in armed effector CD8 T cells , so that the supply of lytic granules is replenished.

This makes it possible for a single CD8 T cell to kill many targets in succession. This increases the chance that infected cells will be recognized as target cells for cytotoxic attack. Thus, armed effector cytotoxic CD8 T cells act in a variety of ways to limit the spread of cytosolic pathogens. The relative importance of each of these mechanisms remains to be determined.

Armed effector cytotoxic CD8 T cells are essential in host defense against pathogens that live in the cytosol, the commonest of which are viruses. These cytotoxic T cells can kill any cell harboring such pathogens by recognizing foreign peptides that are transported to the cell surface bound to MHC class I molecules. Cytotoxic CD8 T cells carry out their killing function by releasing two types of preformed cytotoxic protein: the granzymes, which seem able to induce apoptosis in any type of target cell, and the pore-forming protein perforin, which punches holes in the target-cell membrane through which the granzymes can enter.

These properties allow the cytotoxic T cell to attack and destroy virtually any cell that is infected with a cytosolic pathogen. A membrane-bound molecule, the Fas ligand, expressed by CD8 and some CD4 T cells , is also capable of inducing apoptosis by binding to Fas expressed by some target cells. Cytotoxic T cells kill infected targets with great precision, sparing adjacent normal cells. This precision is critical in minimizing tissue damage while allowing the eradication of infected cells.

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed. Turn recording back on. National Center for Biotechnology Information , U. New York: Garland Science ; Search term. T cell-mediated cytotoxicity. Cytotoxic T cells can induce target cells to undergo programmed cell death Cells can die in either of two ways. Figure 8. Cytotoxic effector proteins that trigger apoptosis are contained in the granules of CD8 cytotoxic T cells The principal mechanism through which cytotoxic T cells act is by the calcium-dependent release of specialized lytic granules upon recognition of antigen on the surface of a target cell.

Activated CD8 T cells and some CD4 effector T cells express Fas ligand, which can also activate apoptosis The release of granule contents accounts for most of the cytotoxic activity of CD8 effector T cells , as shown by the loss of most killing activity in perforin knockout mice.

Cytotoxic T cells are selective and serial killers of targets expressing specific antigen When cytotoxic T cells are offered a mixture of equal amounts of two target cells , one bearing specific antigen and the other not, they kill only the target cell bearing the specific antigen. Summary Armed effector cytotoxic CD8 T cells are essential in host defense against pathogens that live in the cytosol, the commonest of which are viruses.

In this Page. Cytotoxic T cells can induce target cells to undergo programmed cell death Cytotoxic effector proteins that trigger apoptosis are contained in the granules of CD8 cytotoxic T cells Activated CD8 T cells and some CD4 effector T cells express Fas ligand, which can also activate apoptosis Cytotoxic T cells are selective and serial killers of targets expressing specific antigen Cytotoxic T cells also act by releasing cytokines Summary.

Recent Activity. Clear Turn Off Turn On. The human immune system continuously defends us against these threats to our survival. Understanding how immunity works is important for making sense of the news around the risk, spread, and treatment of diseases like COVID also known as coronavirus disease. Please note: HMX online courses in immunology are primarily designed for those working in areas related to health care and the immune system, including diagnostics and treatments.

We understand that not everyone may have the appropriate background, and we encourage you to use other resources as needed to understand any unfamiliar terms and get the most from this material. In this video, you will see a high-level overview of the immune system at work in the context of daily life. The immune system mounts a response against pathogens as they infect an individual and replicate. The response includes both an immediate innate response and a slower adaptive response, which are explained in greater detail in the following sequence.

The innate immune response forms the first line of defense against invading pathogens. Innate immunity includes barriers and a variety of cells and molecules that are part of the rapid response to threats to our health. In this interactive you will be introduced to the various aspects of the innate immune response and the ways in which they work together to prevent and control infection.

Basophils, Mastic Cells and Eosinophils are 3 types of Antiparasitic cells in your body. They are too big to eat. Someone has to kill the cells that are already infected. These Ninja Assassins lurk in the shadows killing virus infected cells. Instant cell death. Pretty cool! Oh well. Finally, there are Humoral Intercellular Cells Figure 5.

The HIC. This team of T and B Cells are your adaptive immune gang. Via interferons Virally infected cells produce and release small proteins called interferons , which play a role in immune protection against viruses. Via antibodies Viruses can also be removed from the body by antibodies before they get the chance to infect a cell.

This binding serves many purposes in the eradication of the virus: Firstly, the antibodies neutralise the virus, meaning that it is no longer capable of infecting the host cell. Secondly, many antibodies can work together, causing virus particles to stick together in a process called agglutination.

Agglutinated viruses make an easier target for immune cells than single viral particles. A third mechanism used by antibodies to eradicate viruses, is the activation of phagocytes. A virus-bound antibody binds to receptors, called Fc receptors, on the surface of phagocytic cells and triggers a mechanism known as phagocytosis , by which the cell engulfs and destroys the virus.

Finally, antibodies can also activate the complement system, which opsonises and promotes phagocytosis of viruses. Bitesize category Pathogens and Disease. Related Articles Yersiniosis. Virus replication. Viruses: Introduction. Ulcerative colitis and Trichuris infection. Microbial infection in cystic fibrosis.