immune 20132014 (1)
Post on 18-Oct-2014
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IMMUNE SYSTEM
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The immune system
• What is the main function of the immune system?
• What is a pathogen?
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The defense mechanisms
• 1st line vs 2nd line vs 3rd line of defenses
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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
• T cell B cell
• Lymphocyte granulocyte
• Plasma cell memory cell
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The chemicals and others
• Perforin Chemokine
• Interferon antibody
• Antigen antigen receptor
• Cd4 Cd8
• Histamine Interleukin
• Lysozyme prostaglandins
• Pyrogens Rh factor
• MHC genes hemolin
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The innate immunity
• What happens to you if you caught a virus or an infection?
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Inflammation and Sepsis
• Release of histamines (pathogen/self cell)
• Dilation and inc permeability of BV (prostaglandin)
• Increased blood flow
• Inflammation (redness and swelling)
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Phagocytic cells
• Neutrophils are first to arrive
• Macrophages will also arrive
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Chemokines
• Messenger chemical
• Attracts phagocytic cells
• Activation of lysozyme action
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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
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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
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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
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Self vs Non-self
• Have you asked yourselves the question who am I?
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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
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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
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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
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Clonal selection
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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
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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
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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
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Graph showing immunological memory
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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
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Immune tolerance for self
• Maturing lymphocytes’ antigen receptors are rendered non-functional
• If antigen receptors cannot be switched off, lymphocytes undergo apoptosis
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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
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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
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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
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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
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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
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Antibodies
• Do not destroy antigens directly
• Rather, neutralizes it or present it as a target for opsonization, agglutination, precipitation, or complement fixation, neutralization
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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
proteins adhere to BV walls
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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
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Rh Factor IgG can cross the placenta ++ = + +- = + - - = -
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Passive vs Active Passive
short-lived
Active Natural vs artificial
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Immunodeficiency vs Autoimmune disease