apoptosis

Examples of apoptosis in the following topics:

• Natural Killer Cells

  • NK cells use wo cytolytic granule-mediated apoptosis to destroy abnormal and infected cells.
  • Apoptosis is a form of "programmed cell death" in which the cell is stimulated by the cytotoxic mechanisms to destroy itself.
  • Unlike with lysis, apoptosis does not degrade DNA, and cells are destroyed cleanly and completely on their own.
  • In apoptosis, these virus particles are destroyed.
  • However, cancer cells often develop genetic mechanisms to prevent apoptosis signals from occurring, so cell lysis is generally more effective.

• Cartilaginous Joints: Synchodroses

  • In puberty, increasing levels of estrogen, in both females and males, leads to increased apoptosis of chondrocytes in the epiphyseal plate.
  • Depletion of chondrocytes due to apoptosis leads to less ossification, and growth slows down and later stops when the cartilage has been completely replaced by bone.

• WBC Function

  • When pathogens are encountered, granule dependent apoptosis (a mechanism of cytotoxicity) may be induced in the pathogen by releasing perforins, granzymes, and proteaseases from their granules.
  • Pathogens that bear the T cell's antigen are destroyed through cytotoxic induced apoptosis and protease activity.

• Hormonal Regulation of the Male Reproductive System

  • Increasing the levels of FSH increases the production of spermatozoa by preventing the apoptosis of type A spermatogonia.

• Lymphocytes

  • They function similarly to NK cells by binding to MHC class I and releasing perforin, granzymes, and proteases to induce apoptosis in a pathogen.
  • Instead of apoptosis, though, defective B cells are killed through other mechanisms such as clonal deletion.

• Graft Rejection and Tissue Typing

  • Rejection is an adaptive immune response via cellular immunity (mediated by killer T cells inducing apoptosis of target cells) as well as humoral immunity (mediated by activated B cells secreting antibody molecules), though the action is joined by components of innate immune response (phagocytes and soluble immune proteins).

• RBC Life Cycle

  • Eryptosis, a form of apoptosis (programmed cell death), is the aging and death of mature RBCs.

• Types of Cytokines Participating in Immune Response

  • Tumor necrosis factor (TNF) are cytokines that induce apoptosis in abnormal cells such as tumor cells.

• Types of Adaptive Immunity

  • Then T-cell produced proteases enter the pathogen and induce an apoptosis response within the cell.

• Development of the Skeleton

  • The hypertrophic chondrocytes (before apoptosis) secrete vascular endothelial cell growth factor, which induces the sprouting of blood vessels from the perichondrium.