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  • 1. Passive .vs. Active Immunity
    • Active Immunity
      • This is immunity where the body is “actively” producing antibodies to fight infection.
      • Ex: You have a throat infection and you are actively creating antibodies to fight it.
      • Vaccination: An injection of a weakened strain of an infectious microbe (pathogen) that causes the body to undergo active immunity (produce antibodies).
    • Passive Immunity
    • This is immunity where antibodies are given to a person from the blood of another person or animal.
    • This immunity only lasts for a short period of time.
    • ex: Breastfeeding mothers pass antibodies to their children through the milk.
  • 2. Natural active acquired immunity: person comes down with measles Artificial active acquired immunity: person is immunized with a vaccine Artificial passive acquired immunity: Person receives serum with antibodies Natural passive acquired immunity: Baby receives antibodies with mother’s milk - colostrum
  • 3.
      • Serum: Fluid that remains after blood has clotted and cells have been removed.
      • Antiserum: Serum containing antibodies to a specific antigen(s). Obtained from injecting an animal (horse, rabbit, goat) with antigen (snake venom, botulism or diphtheria toxin).
      • Serology: The study of reactions between antibodies and antigens.
      • Gamma Globulins: Fraction of serum that contains most of the antibodies.
      • Serum Sickness: Disease caused by multiple injections of antiserum. Immune response to foreign proteins. May cause fever, kidney problems, and joint pain. Rare today.
  • 4.
    • Types of Active Immunity
    • I. 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.
  • 5.
    • II. Cell Mediated Immunity
      • Involves specialized set of lymphocytes called T cells that recognize foreign antigens on the surface of cells, organisms, or tissues:
        • Helper T cells
        • Cytotoxic T cells
        • Delayed Hypersensitivity T (TD) Cells
        • T Suppressor (Ts) Cells
      • T cells regulate proliferation and activity of other cells of the immune system: B cells, macrophages, neutrophils, etc.
      • Defense against:
        • Bacteria and viruses that are inside host cells and are inaccessible to antibodies.
        • Fungi, protozoa, and helminths
        • Cancer cells
        • Transplanted tissue
  • 6.
    • Antigens
    • Most are proteins or large polysaccharides from a foreign organism.
      • Microbes: Capsules, cell walls, toxins, viral capsids, flagella, etc.
      • Nonmicrobes: Pollen, egg white , red blood cell surface molecules, serum proteins, and surface molecules from transplanted tissue.
    • Lipids and nucleic acids are only antigenic when combined with proteins or polysaccharides.
    • Molecular weight of 10,000 or higher.
      • Hapten: Small foreign molecule that is not antigenic. Must be coupled to a carrier molecule to be antigenic. Once antibodies are formed they will recognize hapten.
  • 7.
    • Antigens
    • Epitope :
    • Small part of an antigen that interacts with an antibody.
    • Any given antigen may have several epitopes.
    • Each epitope is recognized by a different antibody.
  • 8. Antibodies
    • Y-shaped protein molecule.
    • Made up of variable and constant regions.
    • Made up of Heavy and Light chains.
    • Produced by B-Lymphocytes
    • Function: Recognize antigens, bind to and deactivate them.
      • Note: Variable region recognizes the anitgens.
  • 9. How an antibody operates/works? Deactivation of a bacterium by an antibody.
  • 10.
    • Immunoglobulin Classes
    • I. IgG
    • Structure: Monomer
    • Percentage serum antibodies: 80%
    • Location: Blood, lymph, intestine
    • Half-life in serum: 23 days
    • Complement Fixation: Yes
    • Placental Transfer: Yes
    • Known Functions: Enhances phagocytosis, neutralizes toxins and viruses, protects fetus and newborn.
  • 11.
    • Immunoglobulin Classes
    • II. IgM
    • Structure: Pentamer
    • Percentage serum antibodies: 5-10%
    • Location: Blood, lymph, B cell surface (monomer)
    • Half-life in serum: 5 days
    • Complement Fixation: Yes
    • Placental Transfer: No
    • Known Functions: First antibodies produced during an infection. Effective against microbes and agglutinating antigens.
  • 12.
    • Immunoglobulin Classes
    • III. IgA
    • Structure: Dimer
    • Percentage serum antibodies: 10-15%
    • Location: Secretions (tears, saliva, intestine, milk), blood and lymph.
    • Half-life in serum: 6 days
    • Complement Fixation: No
    • Placental Transfer: No
    • Known Functions: Localized protection of mucosal surfaces. Provides immunity to infant digestive tract.
  • 13.
    • Immunoglobulin Classes
    • IV. IgD
    • Structure: Monomer
    • Percentage serum antibodies: 0.2%
    • Location: B-cell surface, blood, and lymph
    • Half-life in serum: 3 days
    • Complement Fixation: No
    • Placental Transfer: No
    • Known Functions: In serum function is unknown. On B cell surface, initiate immune response.
  • 14.
    • Immunoglobulin Classes
    • V. IgE
    • Structure: Monomer
    • Percentage serum antibodies: 0.002%
    • Location: Bound to mast cells and basophils throughout body. Blood.
    • Half-life in serum: 2 days
    • Complement Fixation: No
    • Placental Transfer: No
    • Known Functions: Allergic reactions. Possibly lysis of worms.
  • 15.
    • How Do B Cells Produce Antibodies?
      • B cells develop from stem cells in the bone marrow of adults (liver of fetuses).
      • After maturation B cells migrate to lymphoid organs (lymph node or spleen).
      • Clonal Selection : When a B cell encounters an antigen it recognizes, it is stimulated and divides into many clones called plasma cells, which actively secrete antibodies.
      • Each B cell produces antibodies that will recognize only one antigenic determinant.
  • 16. Clonal Selection of B Cells is Caused by Antigenic Stimulation
  • 17.
    • Apoptosis
      • Programmed cell death (“Falling away”).
      • Human body makes 100 million lymphocytes every day. If an equivalent number doesn’t die, will develop leukemia.
      • B cells that do not encounter stimulating antigen will self-destruct and send signals to phagocytes to dispose of their remains.
      • Many virus infected cells will undergo apoptosis, to help prevent spread of the infection.
  • 18.
    • Clonal Selection
      • Clonal Selection: B cells (and T cells) that encounter stimulating antigen will proliferate into a large group of cells.
      • Why don’t we produce antibodies against our own antigens? We have developed tolerance to them.
      • Clonal Deletion: B and T cells that react against self antigens appear to be destroyed during fetal development. Process is poorly understood.
  • 19. Consequences of Antibody Binding
  • 20.
    • Immunological Memory
      • Antibody Titer: The amount of antibody in the serum.
      • Pattern of Antibody Levels During Infection
      • Primary Response:
      • After initial exposure to antigen, no antibodies are found in serum for several days.
      • A gradual increase in titer, first of IgM and then of IgG is observed.
      • Most B cells become plasma cells, but some B cells become long living memory cells .
      • Gradual decline of antibodies follows.
  • 21.
    • Immunological Memory (Continued)
      • Secondary Response:
      • Subsequent exposure to the same antigen displays a faster and more intense antibody response.
      • Increased antibody response is due to the existence of memory cells, which rapidly produce plasma cells upon antigen stimulation.
  • 22. Primary .vs. Secondary Immune Response
  • 23.
    • T Cells and Cell Mediated Immunity
      • Antigens that stimulate this response are mainly intracellular .
      • Requires constant presence of antigen to remain effective.
      • Unlike humoral immunity, cell mediated immunity is not transferred to the fetus.
      • Cytokines: Chemical messengers of immune cells.
      • Over 100 have been identified.
      • Stimulate and/or regulate immune responses.
        • Interleukins: Communication between WBCs.
        • Interferons: Protect against viral infections.
        • Chemokines: Attract WBCs to infected areas.
  • 24.
    • T Cells and Cell Mediated Immunity
      • Cellular Components of Immunity:
      • T cells are key cellular component of immunity.
      • T cells have an antigen receptor that recognizes and reacts to a specific antigen (T cell receptor).
      • T cell receptor only recognize antigens combined with major histocompatability (MHC) proteins on the surface of cells.
        • MHC Class I: Found on all cells.
        • MHC Class II: Found on phagocytes.
      • Clonal selection increases number of T cells.
  • 25. The Pathway of Specific Immune Response Pathogens Pathogens eaten by Macrophage Displays portion of Pathogen on surface Helper-T cell recognizes Pathogen Step 1 Step 2 Step 3
  • 26. Activates B- Cell Activates Cytotoxic T- Cell Memory B-Cell Memory T-Cell Kills Infected Cells Antibodies 
  • 27.
    • Activation of helper T cell
    Self protein displaying an antigen T cell receptor Interleukin-2 stimulates cell division Cytotoxic T cell Interleukin-2 activates other T cells and B cells Cell-mediated immunity (attack on infected cells) Humoral immunity (secretion of antibodies by plasma cells) B cell Helper T cell APC Interleukin-1 activates helper T cell
  • 28.
    • Cytotoxic T cells bind to infected body cells and destroy them
    Cytotoxic T cell binds to infected cell 1 2 3 Perforin makes holes in infected cell’s membrane Infected cell is destroyed INFECTED CELL Perforin molecule Cytotoxic T cell Foreign antigen Hole forming
  • 29. Cellular Immunity .vs. Antibody Immunity
    • Carried out by T-Cells
    • Infected cells are killed by Cytotoxic T –Cells.
    • Carried out by B-cells
    • Antibodies are produced and dumped into blood stream.
    • Antibodies bind to antigens and deactivate them.
    Cellular Immunity Antibody or Humoral Immunity
  • 30. Immune Response Explained
    • Antigen infects cells.
    • Macrophage ingests antigen and displays portion on its surface.
    • Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active.
    • Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.
    • Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells.
    • Active Cytotoxic T-Cells kill infected cells.
    • At the same time, B-Cells divide into Plasma Cells and Memory B- Cells.
    • Plasma cells produce antibodies that deactivate pathogen.
    • Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.
    • Supressor T-Cells stop the immune response when all antigens have been destroyed.
  • 31. Immune Response Summary Displays copy of antigen on surface of cell Cellular Immunity Antibody Immunity Antigen Macrophage Helper T - Cell Active Cytotoxic T-Cell Active B - Cell Kills Infected Cells Memory T- Cell Plasma Cell Memory B-Cell Antibodies Deactivates Antigens
  • 32. Autoimmune Disease
    • Autoimmune diseases are diseases where the immune system begins to attack itself.
      • Ex:
        • Rheumatoid Arthritis – crippling disease of the joints.
        • Lupus – disease of blood and organs.
        • Multiple Sclerosis – disease of nervous system
        • Myasthenia Gravis
    • Cause(s): unknown
    • Cures/Treatments: No known cures. Usually treated with drugs.
  • 33. HIV/AIDS Human immunodeficiency virus Attacks helper T cells Without production of IL-2, there is no second signal, and humoral and cell mediated immunity are shut off. See increase in rare diseases: TB, Kaposi sarcoma, etc.
  • 34.  
  • 35. Allergies
    • Allergy
    • - An exaggerated response by the immune system to an allergen.
    • Allergen: a normally harmless substance that causes an allergic reaction.
    • ex: dust, pollen, mould, food, insect stings
    • Types of Allergic reactions
    • There are two types of allergic reactions.
    • a. Immediate – occurs within seconds and normally lasts for about 30 mins.
    • b. Delayed – takes longer to react and can last for a much longer time.
  • 36. What happens during an allergic reaction?
    • During an allergic reaction antibodies cause histamines to be released from certain cells.
    • Histamines cause:
    • a. Swelling of tissues
    • b. Release of fluids (runny noses and eyes)
    • c. muscle spasms (some cases)
    • Anaphylaxis or anaphylactic shock:
    • This is the sudden and severe allergic reaction to a substance that can cause death.
    • Treatments for Allergies
    • Avoidance of material – especially food.
    • Epinephrine –
    • Antihistamines
  • 37. Immediate Type Hypersensitivity
    • Exposure to certain antigens (allergens) results in the formation of IgE antibodies
    • IgE antibodies bind to mast cells by the Fc end.
    • When the antigen is encountered again, binding with the antibody causes mast cell to release histamine granules.
  • 38.  
  • 39. Delayed Hypersensitivity A type of cell mediated immunity. Td cell – requires usual two signals Second time antigen is encountered, Td cell produces several cytokines that attract and activate macrophages, resulting in an inflammatory reaction. Example: TB skin test