Immune System
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Transcript of Immune System
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Immune SystemBody’s Defenses
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Immune Responses
• Passive• Formation of antibodies• To the fetus thru the placenta, thru breast milk, thru administration of plasma (artificial)
• Active• Formation of your own antibodies• Vaccinations • by contracting an infectious disease by exposure of an antigen
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Innate immune system Adaptive immune system
Response is non-specific Pathogen and antigen specific response
Exposure leads to immediate maximal response
Lag time between exposure and maximal response
Cell-mediated and humoral components
Cell-mediated and humoral components
No immunological memory Exposure leads to immunological memory
Found in nearly all forms of life Found only in jawed vertebrates
Components of the immune system
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2 categories of Defenses• Non-specific • Specific
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Types of Defenses
•Nonspecific defense
• mechanisms are general and protect against many types of pathogens
• Barriers to entry
• Inflammatory rxns
• Protective proteins
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Types of Defenses: non-specific
•Pathogens: • bacteria, fungi, protozoa, and viruses that cause
infection
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Barriers to entry: non-specific
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Layered Defenses• Physical barriers prevent pathogens such as
bacteria and viruses from entering the organism.
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Barriers to entry: Bodily secretions
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Barriers to entry
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Chemical Barriers to Entry• Enzymes• Acids: stomach acid
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Chemical Barriers• Complement System
http://www.youtube.com/watch?v=vbWYz9XDtLw
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Figure 16.21
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Inflammatory Response
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WBCs
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Neutrophils1st WBC to
scence• Phagocytes
capable of diapedesis
• Hallmark of acute infection
• First to arrive on scene
• 40-70%
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Eosinophils
• Mediate for allergies• Limited phagocytic
activity• Strong Chemotaxis
• Attract to injury and infection
• Destroys Antigen/Ab complex
• 2-4%
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Basophils
• Mast cells• Releases histamine:
vasodialator• Heparine: anticoagulant• Releases serotonin/Kinin• .5-1% (smallest
population)
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Monocytes
• Scavengers• Transform into
macrophages, eating bacteria, viruses and tissue debris
• 3rd line of defense• 3-8%
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Monocyte
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Lymphocytes
• Acquired immune response
• SPECIFIC defense system
• 20-25%
• Forms 2 types: • T cells: attack all foreign cells• B cells: produce Ab to get rid
of bacteria and viruses
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Blood cells are produced in the bone marrow from a pluripotent stem cell that can become either a WBC, RBC or Platelet
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http://www.dnatube.com/video/2441/Uptake-of-Bacteria-by-Phagocytes
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Specific DefensesImmunity is a specific defense mechanism.
It is resistance to a particular pathogen or its toxin or metabolic by-product.
Immunity is based upon the ability to distinguish self molecules from non-self.
Molecules that can elicit an immune response are antigens.
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Antigens• The lymphatic system responds to non-self or foreign
antigens, but not to self antigens.
• Shape of antigens allow immune system to be specific
• Antigens: molecules that can elicit an immune response and each having their own receptor• may be proteins, polysaccharides, glycoproteins, or
glycolipids.
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Antigen-Presenting Cells• Macrophages alert
lymphocytes by displaying antigens from engulfed cells.
• Foreign antigens are attached to the macrophage surface by a self protein, part of the major histocompatibility complex (MHC).
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Cellular Immune Response• Helper T cells destroy infected cells and clean up pathogens
• T cells attach to foreign, antigen-bearing cells, cell-to-cell contact.
• Cytokines or lymphokines enhance cellular response to antigens.
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• Helper T cells produce chemical signals to activate cytotoxic T cells, which are WBC carrying pathogen-specific receptors on their surface
• Kill cancer cells and attack foreign tissue
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Lymphocytes Origin• Red bone marrow
releases undifferentiated lymphocytes into the circulation.
• Some become T lymphocytes or T cells in the thymus.
Figure 16.16
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The Immune Responsehttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter24/animation__the_immune_response.html
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Humoral ImmunityRemoving Pathogens at large
• B cells secrete antibodies into the blood: antibody-mediated immunity.
• Helper T cells activate B cells in response to macrophage presentation of antigens.
• Stimulated B cells produce plasma cells or memory cells.
• Plasma cells produce antibodies.
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• AB are released by plasma cells and circulate in blood and lymph
• Ab attach to pathogens, similar to specific binding of cytotoxic T cells
• AB/Antigen complex are then destroyed by general defense like macrophages or proteins that puncture pathogen’s membranes
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• http://bcs.whfreeman.com/thelifewire/content/chp18/1804s.swf
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Types of T Cells• Helper T cells
• stimulate B cells to produce antibodies• CD4 cells are prime targets of HIV
• Memory T cells• produced upon initial antigen exposure and protect
against delay in future exposure• Cytotoxic T cells
• release perforin to destroy cells that present foreign antigens
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B Cell Activation• Activated helper T cell
releases cytokines.
• Cytokines stimulate B cell proliferation.
Figure 16.19
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B Cell Activation• Some B cells become
plasma cells that secrete antibodies that bind antigens.
• Antibodies (immunoglobulins) are globular proteins composed of four chains.
• Ends of the molecule contain antigen-binding sites.
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Long Term Protection• Memory Cells
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Long Term• Vaccines
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Long Term• How pathogens evade immunity
• Antigen shifting
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Immunoglobulins
• Immunoglobulin G• IgG, gamma globulin, 80% of
antibodies• defends against bacteria,
viruses, toxins• found in blood plasma and
tissue fluid• activates complement
Figure 16.20
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Immunoglobulins• Immunoglobulin A
• IgA, 13% of antibodies• found in exocrine secretions• defends against bacteria and
viruses
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Immunoglobulins• Immunoglobulin M
• IgM, 6% of antibodies, found in plasma• activates complement
• Immunoglobulin D• IgD, found on mast cells• activates B cells
• Immunoglobulin E• IgE, found in exocrine secretions• promotes inflammation and allergic reactions
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Antibody Actions• Antibodies attach directly to antigens
• agglutination, precipitation, neutralization• Antibodies activate complement
• Combination with antigens exposes reactive sites on complement which results in• opsonization increasing phagocytosis susceptibility• chemotaxis attracting neutrophils and
macrophages• inflammation to prevent spread of antigens• lysis of cell membranes
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Innate Immunity• Humoral
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Innate Immunity• Cellular Barriers
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Adaptive Immunity
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• http://gtm-media.discoveryeducation.com//downloaddirector/downloadFile.aspx?thefile=10053\sec9296_256.mov&realname=The_Immune_System