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Lecture13 Immunity
 

Lecture13 Immunity

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    Lecture13 Immunity Lecture13 Immunity Presentation Transcript

    • Immunity Overview
    • Types Of Immunity
      Innate Immunity
      Acquired Immunity
      Naturally Acquired Active Immunity
      Artificially Acquired Active Immunity
      Naturally Acquired Passive Immunity
      Artificially Acquired Passive Immunity
    • Overview of Immunity
    • Naturally Acquired Active Immunity
      • Naturally acquired active immunity is obtained when a person is exposed to antigens in the course of daily life, direct exposure.
      • The immune system then responds by producing antibodies and specialized lymphocytes. Usually, the immunity is for a long term.
      • Examples, include measles, pox.
    • Artificially Acquired Active Immunity
      Artificially acquired active immunity results from
      vaccination or immunizations.
      Vaccination introduces specially prepared antigens into the body.
      These antigens are no longer able to cause disease, but they are still able to stimulate an immune response.
    • Naturally Acquired Passive Immunity
      Naturally acquired passive immunity involves the
      natural transfer of antibodies from a mother to a
      child.
      An expectant mother is able to pass some
      of her antibodies to her fetus across the placenta.
      In addition, certain antibodies are also passed
      from the mother to the child during breast feeding.
      Generally immunity lasts only as long as the antibodies are active usually a few weeks or 6 months.
    • Artificially Acquired Passive Immunity
      Artificially acquired passive immunity involves an
      injection of antibodies into the body.
      These antibodies come from an animal or human who is already immune to the disease.
    • Immunity Overview
      Immunity: The body's ability to fight off harmful micro-organisms –PATHOGENS- that invade it.
      The immune system produces antibodies or cells that can deactivate pathogens.
      Fungi, protozoans, bacteria, and viruses are all potential pathogens.
      Antigen: Molecules from a pathogen or foreign organism that provoke a specific immune response.
    • The Immune System - includes all parts of the body that help in the recognition and destruction of foreign materials.  White blood cells, phagocytes and lymphocytes, bone marrow, lymph nodes, tonsils, thymus, and spleen are all part of the immune system.  
    • Function of the immune system
      Destroy pathogens
      Detect and kill abnormal cells
      Remove dead cells and other debris from the body
    • The Immune System is the Third Line of Defense Against Infection
      • Third-Line Defenses - Sometimes the second line of defense is still not enough and the pathogen is then heading for the body's last line of defense, the immune system.  
      • The immune system recognizes, attacks, destroys, and remembers each pathogen that enters the body.  It does this by making specialized cells and antibodies that render the pathogens harmless.
      •  Unlike the first line and second line defense the immune system differentiates among pathogens.
      • For each type of pathogen, the immune system produces cells that are specific for that particular pathogen. 
      • An antibody is a protein produced in response to an antigen.
      • Antigens are macromolecules that elicit an immune response in the body. The most common antigens areproteins and polysaccharides.
    • Antigens can enter the body from the environment. These include
      • inhaled macromolecules (e.g., proteins on cat hairs that can trigger an attack of asthma in susceptible people)
      • ingested macromolecules (e.g., shellfish proteins that trigger an allergic response in susceptible people)
      • molecules that are introduced beneath the skin (e.g., on a splinter or in an injected vaccine)
      • antigens can be generated within the cells of the body. These include
      • proteins encoded by the genes of viruses that have infected a cell
      • Proteins that are encoded by mutant genes; such as mutated genes in cancer cells
    • Specific defenses
      • protect against specifically identified threats (i.e. may defend against one particular bacterial infection but not a different one)
      • many specific defenses develop after birth upon exposure to an antigen; an antigen can be a pathogen (disease-causing organism), foreign protein (e.g. toxin), abnormal or infected body cell, foreign tissue transplant
      • specific defenses produce a state of long-term protection known as “Immunity”
    • Immunity
      Immunity = specific resistance to disease
      • depends on coordinated activity of T & B lymphocytes
      • Humoral immunity involves the antibodies and the B cells that they secret them; is directed against extracellular pathogens
      • Cellular immunity involves T lymphocyte that directly attack other cells; defense against abnormal cells & intracellular pathogens
    • Humoral and cellular immunity
    • Immunity is the result of the action of two types lymphocytes, the B lymphocytesand the T lymphocytes.
      B cells produce antibodies that are secreted into the blood and lymph.
       
      T cells attack the cells that have antigens that they recognize.
    • Shared feature of B & T lymphocyte
      Specificity of receptors: Both B & T lymphocyte have specific receptor for specific antigen
      Diversity of receptors: There are huge numbers of different lymphocyte each with its own unique antigen receptor
      Regulation of activation: Activation of B & T cells leads to process clonal expansion
      Memory: Respond to subsequent exposure to the same antigen
    • Antigen: Self Antigen
      There are a vast number of antigen outside the body. There are also internal antigen called self antigen.
      Lymphocyte must recognize antigen from pathogen while ignoring self antigen
    • Antigen receptor- Specificity
      The surface of mature B & T lymphocyte studded with lymphocyte antigen receptor that allows these cells to identify their particular antigen shape
      The antigenic specificity of B & T lymphocyte is determined by the shape of their antigen receptor
      B & T cells have a related structure and similar function, there are differences in their shape and the way they interact with antigen
    • Antigen receptor
      The B cell antigen receptor is Y-shape antibody molecule and directed against antigen in the extracellular fluid
      When the antigen occupy the antigen binding site on the B cell receptors, the receptor signals the cell that antigen found
    • Antigen receptor
      T lymphocyte receptor is not:
      Membrane bound antibody
      Y-Shaped
      T cell directed against the body’s own cells when they are invaded
    • Antigen receptor
      When antigen bind receptors and activate the receptors, the cell divides and make clone with identical receptor
      This matching mechanism called clonal selection
    • Humoral (Antibody-Mediated) Immunity
      Involves production of antibodies against foreign antigens.
      Antibodies are produced by a subset of lymphocytes called B cells.
      B cells that are stimulated will actively secrete antibodies and are called plasma cells.
      Antibodies are found in extracellular fluids (blood plasma, lymph, mucus, etc.) and the surface of B cells.
      Defense against bacteria, bacterial toxins, and viruses that circulate freely in body fluids, before they enter cells.
      Also cause certain reactions against transplanted tissue.