apoptosis

(noun)

The process of programmed cell death by which cells undergo an ordered sequence of events which lead to death of the cell. This occurs during growth and development of the organism, as a part of normal cell aging, or as a response to cellular injury.

Related Terms

Examples of apoptosis in the following topics:

  • Natural Killer Cells

    • Typically immune cells detect MHC that is present on infected cell surfaces, triggering cytokine release and causing lysis or apoptosis.
    • The granzymes then break down the target cell, inducing death by either apoptosis or osmotic cell lysis.
    • Natural cytotoxicity receptors directly induce apoptosis after binding to ligands that directly indicate infection of a cell.
    • The MHC dependent receptors (described above) use an alternate pathway to induce apoptosis in infected cells.
    • Functions of NK cells include: Cytolytic Granule Mediated Cell Apoptosis; Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC); Cytokine induced NK and CTL activation; Missing 'self' hypothesis; Tumor cell surveillance; NK cell function in adaptive response; NK cell function in pregnancy; and NK cell evasion by tumor cells .

  • Type IV (Delayed Cell-Mediated) Reactions

    • Cytotoxic T cells cause death by apoptosis without using cytokines.
    • 1. activating antigen-specific cytotoxic T-lymphocytes that are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens

  • Cancer Viruses

    • This can result from having control of their own growth signals, losing sensitivity to anti-growth signals, and losing the ability to undergo apoptosis, or programmed cell death.

  • Damage to the Cell Wall

    • Damage to the cell wall disturbs the state of cell electrolytes, which can activate death pathways (apoptosis or programmed cell death).

  • Cooperation Among Microorganisms

    • On a microscopic level, this happens with programmed cell death, or apoptosis.

  • Cell-Mediated Autoimmune Reactions

    • Dendritic cells that are defective in apoptosis can lead to inappropriate systemic lymphocyte activation and consequent decline in self-tolerance.

  • Viral Pneumonia

    • This invasion often leads to cell death, in which either the virus directly kills the cell, or the cell self-destructs through apoptosis.

  • Antibody Genes and Diversity

    • B cells that express higher affinity antibodies on their surface will receive a strong survival signal during interactions with other cells, whereas those with lower affinity antibodies will not, and will die by apoptosis.

  • Interferons

    • They also limit viral spread by increasing p53 activity, which kills virus-infected cells by promoting apoptosis.

  • Double-Stranded DNA Viruses: Adenoviruses

    • The goal of these proteins is threefold: to alter the expression of host proteins necessary for DNA synthesis; to activate other viral genes (such as the virus-encoded DNA polymerase); and to avoid premature death of the infected cell by the host-immune defenses (blockage of apoptosis, blockage of interferon activity, and blockage of MHC class I translocation and expression).