Immune 20132014 (1)

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  • Self recognition is important in an immune response Presence of receptors/markers in pathogens that enter the body Very efficient, even undigested proteins are considered as antigens
  • Single lymphocyte has ~100,000 receptors for antigen Differentiation of unspecialized lymphocytes gives rise to diversity of the antibody or receptor Makes it possible to respond to different pathogens
  • Re-exposure- response is faster, greater magnitude and more prolonged
  • Immune 20132014 (1)

    1. 1. IMMUNE SYSTEM
    2. 2. The immune system • What is the main function of the immune system? • What is a pathogen?
    3. 3. The defense mechanisms • 1st line vs 2nd line vs 3rd line of defenses
    4. 4. Give the function of these cells • Monocytes APC coelomocytes • Macrophages Basophil • Neutrophil Eosinophil • Mast cell NK cell • Cytokine cytotoxic T cell • effector cell helper T cell • memory cell suppressor T cell
    5. 5. The chemicals and others • Perforin Chemokine • Interferon antibody • Antigen antigen receptor • Cd4 Cd8 • Histamine Interleukin • Lysozyme prostaglandins • Pyrogens Rh factor
    6. 6. The innate immunity • What happens to you if you caught a virus or an infection?
    7. 7. Inflammation and Sepsis • Release of histamines (pathogen/self cell) • Dilation and inc permeability of BV (prostaglandin) • Increased blood flow • Inflammation (redness and swelling)
    8. 8. Phagocytic cells • Neutrophils are first to arrive • Macrophages will also arrive
    9. 9. Chemokines • Messenger chemical • Attracts phagocytic cells • Activation of lysozyme action
    10. 10. Severe infection • Fever is an immune response to severe infection – Can be caused by the pathogens – May be due to pyrogens released by some leukocytes – Can facilitate phagocytosis Septic shock- high fever, hypotension
    11. 11. Antimicrobial proteins • Proteins that attack microbes or stall reproduction of microbes • Lysozyme is an example • Also, presence of the complement system – Made up of 20 serum proteins – Action: lysis or attraction of phagocytic cells – Is also part of specific immune response
    12. 12. Interferons – Secreted by virus-infected cells – Neighboring cells are stimulated to produce chemicals that can inhibit viral infection – Not virus-specific – A specific type of interferon activates phagocytes
    13. 13. Self vs Non-self • Have you asked yourselves the question who am I?
    14. 14. Self vs Non-self • Lymphocytes react on special surface glycoproteins encoded by genes called Major Histocompatibilty Complex (MHC) • In Humans, Human Leukocyte Antigens (HLA) • Class I MHC- Almost all nucleated cells • Class II MHC- macrophages, B cells, activated T cells, cell in the interior of the thymus Varies from one person to another
    15. 15. Specific immunity: the third line of defense • Lymphocytes- cells responsible for the specific immune response • There are two types: B cells and T cells (NK cells another type) • Antigen- molecules that elicit specific response from lymphocyte – E.g. Molecules from bacteria, fungi, virus, parasitic worms • Antigens activate B cell in producing antibodies
    16. 16. Recognition of antigens by B cells and T cells • Specificity is possible because of membrane- bound antigen receptor • B cell antigen receptor- transmembrane version of antibodies – Also called membrane antibodies • T cell antigen receptor- called T cell receptor – Structurally related to membrane antibodies – T cell receptor never released in secreted form
    17. 17. Clonal selection
    18. 18. Clonal selection • Antigen binds to a specific antigen receptor (B cell) • B cell produces its clone • Some B cells become plasma cells (short-lived) that can secrete antibodies to the specific antigen – Plasma cells- also called effector cells • Some B cells become memory cells (long-lived) for re-exposure to the antigen
    19. 19. Immunological memory • Primary immune response- selective proliferation and differentiation of lymphocytes upon first exposure – 10-17 days to develop maximum effector cells – Selected B cells and T cells produce their respective effector cells
    20. 20. Immunological memory • Secondary immune response- re-exposure to the same antigen – response is faster, greater magnitude, more prolonged – Also, more antibodies are produced – Antibodies have greater affinity to the antigens – Secondary response is called immunological memory
    21. 21. Graph showing immunological memory
    22. 22. Lymphocyte development • All blood cells develop from pluripotent cells • Lymphocytes also develop from pluripotent cells • T cells- mature in the thymus • B cells- mature in the bone marrow
    23. 23. Immune tolerance for self • Maturing lymphocytes’ antigen receptors are rendered non-functional • If antigen receptors cannot be switched off, lymphocytes undergo apoptosis
    24. 24. The other cells.... • Cytotoxic T cells- kill cells through lysis • Helper T cells- bind to antigen cell and secretes cytokine • Antigen-presenting cells (APCs)- engulf bacteria (virus) and present fragment of these pathogens to other lymphocytes
    25. 25. Humoral response and cell-mediated response • Humoral immunity- involves B cell activation, production of antibodies in blood plasma and lymph called humor • Cell-mediated immunity- action of T cells
    26. 26. Overview of humoral response • Macrophage engulfs the pathogen • Class II MHC binds to fragment of pathogen • MHC-antigen complex is presented by the phagocytic cell • A helper T cell with specific receptor for the antigen makes contact with the macrophage and releases cytokines
    27. 27. Overview of humoral response • Activated T cell presents the antigen to a B cell • Cytokines activates the B cell • Activated B cells differentiate into plasma and memory cells • Plasma cells will produce the specific antibodies
    28. 28. Cell-mediated immune response • Occurs when antigen displayed by APC activates Cytotoxic T cell • Cytotoxic cell can differentiate to Memory T cells or active cytotoxic T cells • Active against cancer cells and pathogens • Kills these cell through lysis
    29. 29. Antibodies • Do not destroy antigens directly • Rather, neutralizes it or present it as a target for opsonization, agglutination, precipitation, or complement fixation, neutralization
    30. 30. Antibodies • Opsonization- coating of antigens by antibodies to facilitate phagocytos • Neutralization- binds to the antigen and inactivates it • Agglutination- clumping of bacteria or virus to effectively neutralize or opsonize it • Complement fixation or precipitation- immune adherence occurs – Microbes coated with antibodies and complement
    31. 31. The ABO blood type • A and B are the antigens • Type A has antigen A and antibody B • Type B has antigen B and antibody A • Type AB has both antigen but no antibody • Type O has no antigen but has both antibody  IgM not IgG
    32. 32. Rh Factor  IgG can cross the placenta  ++ = +  +- = +  - - = -
    33. 33. Passive vs Active  Passive  short-lived  Active  Natural vs artificial
    34. 34. Immunodeficiency vs Autoimmune disease

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