Self molecules

(noun)

Those components of an organism's body that can be distinguished by the immune system from foreign substances.

Related Terms

  • Adaptive (acquired) immunity
  • Innate immunity

Examples of Self molecules in the following topics:

  • Elements of Life

    • In such a reducing atmosphere, electrical activity can catalyze the creation of certain basic small molecules (monomers) of life, like amino acids.
    • A fundamental question is about the nature of the first self-replicating molecule.
    • The polymerization of nucleotides into random RNA molecules might have resulted in self-replicating ribozymes (RNA world hypothesis).
    • Using this apparatus, and using conditions thought to approximate the conditions on pre-biotic earth, they were able to catalyze the molecules of life like amino acids.
  • Clonal Selection and Tolerance

    • Central tolerance is the mechanism by which newly developing T cells and B cells are rendered non-reactive to self.
    • The theory that self-tolerance is 'learned' during lymphocyte development was a major conceptual contribution to immunology.
    • However, they exert their immune suppression in the periphery on other self (or foreign)-reactive T cells.
    • Positive selection ensures maturation of T cells whose receptors bind weakly to self major histocompatibility complex molecules.
    • "Self"-antigens from the body's own tissues 4.
  • T Cell Receptors

    • T lymphocytes have a dual specificity: they recognize polymorphic residues of self major histocompatibility complex (MHC) molecules, which accounts for their MHC restriction; they also recognize residues of peptide antigens displayed by these MHC molecules, which is responsible for their specificity.
    • MHC molecules and peptides form complexes on the surface of antigen presenting cells (APCs).
    • T cells also express other membrane receptors that do not recognize antigens but participate in responses to antigens; these are collectively called 'accessory molecules'.
    • The physiologic role of some accessory molecules is to deliver signals to the T cells that function in concert with signals from the TCR complex to fully activate the cell.
  • Natural Killer Cells

    • MHC I molecules are proteins on the surfaces of all nucleated cells which help the immune system distinguish between "self" and "non-self."
    • If the cell is infected, the MHC I molecules display fragments of proteins from the infectious agents to T-cells.
    • Healthy cells do not display any proteins and will be ignored by the immune system, while the cells identified as "non-self" by foreign proteins will be attacked by the immune system.
    • An infected cell (or a tumor cell) is often incapable of synthesizing and displaying MHC I molecules appropriately.
    • This process can deplete host MHC I molecules on the cell surface, which prevents T-cells from recognizing them, but which NK cells detect as "unhealthy" or "abnormal" while searching for cellular MHC I molecules.
  • Maturation of T Cells

    • These are expressed by thymic cortical epithelial cells that express both MHC I and MHC II molecules on the surface of cortical cells.
    • Double-positive cells (CD4+/CD8+) that are positively selected on MHC class II molecules will eventually become CD4+ helper T cells, while cells positively selected on MHC class I molecules mature into CD8+ cytotoxic T cells.
    • But if there is a signal interruption, it will instead reduce CD4 molecules, eventually becoming a CD8+, single positive cell.
    • Negative selection removes thymocytes that are capable of strongly binding with self-antigens presented by MHC.
    • While in the medulla, they are again presented with self-antigen in complex with MHC molecules on thymic epithelial cells.
  • Acid-Base Properties of Water

    • Water is capable of acting as either an acid or a base and can undergo self-ionization.
    • Under standard conditions, water will self-ionize to a very small extent.
    • The self-ionization of water refers to the reaction in which a water molecule donates one of its protons to a neighboring water molecule, either in pure water or in aqueous solution.
    • The self-ionization of water produces hydronium and hydroxide ions in solution.
    • Explanation of self-ionization of water and the formation of hydronium and hydroxide ions.
  • Specialized Equilibrium Constants

    • Common reactions, such as the self-ionization of water, have specially named equilibrium constants.
    • The self-ionization, or autodissociation, of water is a reaction that occurs to a very small extent in neutral water.
    • In this process, one molecule of water donates a proton to a neighboring water molecule, which yields hydronium and hydroxide ions.
    • A water molecule is protonated to form a hydronium ion in the process.
    • A water molecule protonates a neighboring water molecule, yielding hydronium and hydroxide ions.
  • Immunoassays for Disease

    • Immunology is the study of molecules, cells, and organs that make up the immune system.
    • The function of the immune system is to recognize self antigens from non-self antigens and defend the body against non-self (foreign) agents.
    • Because antibodies can be produced against any type of macromolecule, antibody-based techniques are useful in identifying molecules in solution or in cells.
    • Recent methods employ pure antibodies or antigens that have been immobilized on a platform and that can be measured using an indicator molecule.
  • Antigens and Antigen Receptors

    • Antigens are molecules that initiate the immune response and can be bound by antibodies.
    • "Self" antigens are usually tolerated by the immune system; whereas "non-self" antigens can be identified as invaders and can be attacked by the immune system.
    • Cells present their immunogenic-antigens to the immune system via a histocompatibility molecule.
    • The fragments are then presented on the cell surface in the complex with MHC class I molecules.
    • In order to keep the cytotoxic cells from killing cells just for presenting self-proteins, self-reactive T cells are deleted from the repertoire as a result of tolerance (also known as negative selection).
  • Fluid Mosaic Model

    • Hydrophobic, or water-hating molecules, tend to be non-polar.
    • A phospholipid molecule consists of a three-carbon glycerol backbone with two fatty acid molecules attached to carbons 1 and 2, and a phosphate-containing group attached to the third carbon.
    • They interact with other non-polar molecules in chemical reactions, but generally do not interact with polar molecules.
    • When placed in water , hydrophobic molecules tend to form a ball or cluster.
    • This recognition function is very important to cells, as it allows the immune system to differentiate between body cells (called "self") and foreign cells or tissues (called "non-self").
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