target cell

Examples of target cell in the following topics:

• Target Cell Specificity

  • Hormones target a limited number of cells (based on the presence of a specific receptor) as they circulate in the bloodstream.
  • An XY fetus will develop along a female pathway if the target cells fail to respond to androgen.
  • In endocrinology, target cells can refer to the cells where hormones have an effect.
  • Target cells are capable of responding to hormones because they display receptors to which the circulating hormone can bind.
  • Modulation of these factors can control target cell response.

• Forms of Signaling

  • The main difference between the different categories of signaling is the distance that the signal travels through the organism to reach the target cell.
  • Hormones travel the large distances between endocrine cells and their target cells via the bloodstream, which is a relatively slow way to move throughout the body.
  • Because of their form of transport, hormones get diluted and are present in low concentrations when they act on their target cells.
  • This means the signaling cell and the target cell can be the same or a similar cell (the prefix auto- means self, a reminder that the signaling cell sends a signal to itself).
  • In chemical signaling, a cell may target itself (autocrine signaling), a cell connected by gap junctions, a nearby cell (paracrine signaling), or a distant cell (endocrine signaling).

• Natural Killer Cells

  • After a pathogen enters the body, infected cells are identified and destroyed by natural killer (NK) cells, which are a type of lymphocyte that can kill cells infected with viruses or tumor cells (abnormal cells that uncontrollably divide and invade other tissue).
  • As such, NK cells offer a complementary check for unhealthy cells, relative to T cells.
  • After the NK cell detects an infected or tumor cell, its cytoplasm secretes granules comprised of perforin: a destructive protein that creates a pore in the target cell.
  • A granzyme, a protease that digests cellular proteins, induces the target cell to undergo programmed cell death, or apoptosis.
  • Phagocytic cells then digest the cell debris left behind.

• Natural Killer Cells

  • Often NKT cell activity promotes NK cell activity by secreting IFNγ.
  • NK cells paralyze target cells using the cytolytic protein perforin and a variety of protease enzymes.
  • An NK cell will first use perforin to create pores in a target cell, allowing it to inject granzymes through an aqueous channel.
  • The granzymes then break down the target cell, inducing death by either apoptosis or osmotic cell lysis.
  • 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 .

• Cancer and Translational Control

  • Both forms appear to be involved in initiating controlled cell death mechanisms in normal cells.
  • However, in colon cancer cells, expression of the long form results in increased cell growth instead of cell death.
  • With an increased understanding of gene regulation and gene function, medicines can be designed to specifically target diseased cells without harming healthy cells.
  • Undoubtedly, more targeted therapies will be developed as scientists learn more about how gene expression changes can cause cancer .
  • Scientists are using knowledge of the regulation of gene expression in individual cancers to develop new ways to treat target diseased cells and prevent the disease from occurring.

• White Blood Cells

  • White blood cells, also called leukocytes, play an important role in the body's immune response by identifying and targeting pathogens.
  • They are primarily involved in the immune response to identify and target pathogens, such as invading bacteria, viruses, and other foreign organisms.
  • They include B cells, T cells, and natural killer cells.
  • T cells attack viruses, fungi, some bacteria, transplanted cells, and cancer cells.
  • One reason that HIV poses significant management challenges is because the virus directly targets T cells by gaining entry through a receptor.

• Inhibiting Cell Wall Synthesis

  • β-Lactam (beta-lactam) and glycopeptide antibiotics work by inhibiting or interfering with cell wall synthesis of the target bacteria.
  • Two types of antimicrobial drugs work by inhibiting or interfering with cell wall synthesis of the target bacteria.
  • Antibiotics commonly target bacterial cell wall formation (of which peptidoglycan is an important component) because animal cells do not have cell walls.
  • Diagram depicting the failure of bacterial cell division in the presence of a cell wall synthesis inhibitor (e.g. penicillin, vancomycin).1- Penicillin (or other cell wall synthesis inhibitor) is added to the growth medium with a dividing bacterium.2- The cell begins to grow, but is unable to synthesize new cell wall to accommodate the expanding cell.3- As cellular growth continues, cytoplasm covered by plasma membrane begins to squeeze out through the gap(s) in the cell wall.4- Cell wall integrity is further violated.
  • The cell continues to increase in size, but is unable to "pinch off" the extra cytoplasmic material into two daughter cells because the formation of a division furrow depends on the ability to synthesize new cell wall.5- The cell wall is shed entirely, forming a spheroplast, which is extremely vulnerable relative to the original cell.

• Specific T-Cell Roles

  • T helper cells assist the maturation of B cells and memory B cells while activating cytotoxic T cells and macrophages.
  • Cytotoxic T cells (TC cells, or CTLs) destroy virus-infected cells and tumor cells, and cause much of the damage in in transplant rejection and autoimmune diseases.
  • They recognize their targets by binding to antigens associated with MHC class I, which is present on the surface of nearly every cell of the body.
  • The cytotoxic enzymes and proteases travel to their target cells through a microtubule cytoskeleton.
  • Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells), which have different properties and release different cytokines.

• Natural Killer Cells

  • The role of NK cells is similar to that of cytotoxic T cells in the adaptive immune response.
  • NK cells provide rapid responses to virus-infected cells and respond to tumor formation by destroying abnormal and infected cells.
  • Unlike phagocytes, NK cells do not need their targets to be opsonized (marked) by antibodies before they can act, allowing for a much faster immune reaction.
  • Upon binding to a cell slated for killing, perforin forms pores in the cell membrane of the target cell, creating an aqueous channel through which the granzymes and associated molecules can enter, inducing either apoptosis or osmotic cell lysis (a form of cell necrosis).
  • Virus-infected cells destroyed by cell lysis release their replicated virus particles into the body, which infects other cells.

• Cell Signaling and Cell Death

  • When a cell is damaged, unnecessary, or dangerous to an organism, a cell can initiate the mechanism for cell death known as apoptosis.
  • When a cell is damaged, superfluous, or potentially dangerous to an organism, a cell can initiate a mechanism to trigger programmed cell death, or apoptosis.
  • T-cells are immune cells that bind to foreign macromolecules and particles, targeting them for destruction by the immune system.
  • Normally, T-cells do not target "self" proteins (those of their own organism), a process that can lead to autoimmune diseases.
  • If the T-cell receptor binds to self proteins, the cell initiates apoptosis to remove the potentially dangerous cell.