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An Overview: Nonspecific vs. Specific Defense Mechanisms

An Overview: Nonspecific vs. Specific Defense MechanismsBody Defenses: An OverviewNonspecific Defenses Hinder entry of most pathogens (disease causing organisms) Prevent spread of disease Strengthen immune responseBody Defenses: An OverviewSpecific Defenses: The immune System Destroys foreign cells that cause disease Recognize self from non-self Inactivate toxins and other foreign chemicalsNonspecific ResponseSurface Barriers: 1stline of Skin(epidermis) Forms mechanical barrier Acid secretion inhibits bacterial growth Keratin provides resistance against bacterial enzymes, acids, membranes Trap microorganisms in respiratory and digestive tractsElectron Micrograph ofEscherichiacoli with PiliE.

Immune Response: Roles of Cells involved 1. Macrophages » Antigen presenter (APC = Antigen Presenting Cell) » Activate Helper T Cells (by contact w/ displayed antigen) » Releases cytokines: Enhances Helper T Cell activation 2. Helper T Cells » Stimulate the humoral and cell-mediated response against specific antigens » Activated by Macrophages (Cytokines and contact w/

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Transcription of An Overview: Nonspecific vs. Specific Defense Mechanisms

1 An Overview: Nonspecific vs. Specific Defense MechanismsBody Defenses: An OverviewNonspecific Defenses Hinder entry of most pathogens (disease causing organisms) Prevent spread of disease Strengthen immune responseBody Defenses: An OverviewSpecific Defenses: The immune System Destroys foreign cells that cause disease Recognize self from non-self Inactivate toxins and other foreign chemicalsNonspecific ResponseSurface Barriers: 1stline of Skin(epidermis) Forms mechanical barrier Acid secretion inhibits bacterial growth Keratin provides resistance against bacterial enzymes, acids, membranes Trap microorganisms in respiratory and digestive tractsElectron Micrograph ofEscherichiacoli with PiliE.

2 Coli can cause urinary tract infections and traveler's diarrhea Flushing Away of Bacteria Lacking Pili Lacking any means of adherence, urine typically flushes bacteria from the fight back! Bacteria with Pili Resisting such asNeisseria gonorrhoeaeusepilito adhere to the mucous membranes of the urethra and thus resist the flushing action of the fight back! SalmonellaInvading an Intestinal MucosalEpithelial Cell Salmonellaadheres to themicrovilliof intestinalmucosalepithelial cells. Triggerspseudopodsthat engulf the Salmonellaand place it in a vacuole. Salmonellareplicate within the vacuole and are subsequently released from the cell.

3 Response 1stline of Defense (cont.) juice kills lining of vagina kills & saliva Contain lysozyme kills hairs Filter and trap mucus away from lower respiratory tractFirst-line respiratory defenses2ndline of Nonspecific Defense : Nonspecific cellular : macrophages & neutrophils Feed on pathogens that penetrate membrane barriers Display antigen to enhance immune response ( Specific response) killer cells Lyse and kill cancerous and virally infected cellsNK Cell destroying a target cellPhagocytosis by a MacrophagePhagocytosis Animation by Cells Alive: How to get to the on Immunology on Ouch anatomy of a splinter to bottom of page and Click on Next on Phagocytosis how white cells eat microbes 2ndline of Nonspecific Defense : Nonspecific chemical defensesInflammatory response spread of damaging agents cell debris and in tissue when tissues are damaged or irritated Physical trauma, heat, chemicals, pathogensInflammatory Response: a simplified viewAnimation of Inflammatory Response (cont.)

4 Cardinal signs: Redness, heat, swelling, pain Sequence of tissue & kinins + capillaries become leaky (swelling) receptors activated s(B & T cells + phagocytes) attractedInflammatory Response: a detailed viewNonspecific chemical defenses(2ndline of Nonspecific Defense )Anti-microbial protein system More than 20 plasma proteins Produced by the liver Inactive until contact with inflammatory response Vasodilatation Attract phagocytesRoles of Complement Protein System(cont.) foreign cells Poke holes in membrane water enters cells Cause foreign cells to stick together Yummy for phagocytes enhances phagocytosisAnimation of Phagocytosis Enhanced by fight back!

5 Bacterial Resistant to some bacteria, a capsule covers the opsoninC3b on bacterial cell binding to C3b receptors on the surface of phagocytes: Bacterial fight back! Bacillus anthracisin Action: Inhalation AnthraxSource: Scientific American(March 2002) cells ingest B. anthracisspores and carry them to lymph nodes In blood and inside macrophage: Spores transform into actively dividing cells B. anthraciscells erupt from macrophage B. anthracis cells evades destruction Produce capsule that protects them from digestion by macrophages and antibodies from B-cells Produce toxin enters and that impairs immune cell functionBacterial fight back!

6 Blocking Phagosome Formationby Depolymerizing bacteria secrete proteins which depolymerize the phagocyte'sactinmicrofilaments used for phagocytic engulfment. Chemicals (Cont.) Released by virally infected cells Stimulate neighboring cells to produce anti-viral proteins (AVP) AVP s inhibit viral reproduction in nearby cells InterferonsAnti-microbial Chemicals (Cont.) Secreted by macrophages Cause mild fever Slows down bacterial reproductionThe 3rd Line of Defense : Specific Defense immune systemthat seeks to destroy or inactivate specificantigens (foreign molecules and cells) Specific : responds to particular foreign response: body wide.

7 Quicker and stronger response to previously encountered pathogensBranches Of The immune immunity Where B-cellscirculating in the body s fluids produce antibodies in response to a immunity Where killer T-cells(cytotoxic T-cells) destroy cancer cells virus and bacteria infected cells cells of foreign graftsHumoral and Cell-mediated ImmunityImmune Response:Roles of Cells Antigen presenter (APC = Antigen Presenting Cell) Activate Helper T Cells (by contact w/ displayed antigen) Releases cytokines: Enhances Helper T Cell T Cells Stimulate the humoral and cell-mediated response against Specific antigens Activated by Macrophages (Cytokines and contact w/ presented antigen) Activate B-Cells and Killer T-cells by secreting cytokinesHumoral lymphocytes (B-cells) Produced and mature in the bone marrow Mature = become immunocompetent = ability to respond to an antigen by binding to cells that bind to self-antigens are to and concentrate in lymphatic antibodies Specific for Specific antigens Plasma cells vs.

8 Memory cellsHumoral ImmunityClonal Selection TheoryAntibody Structure:Y-shaped moleculesEach Antibody binds to a Specific EpitopeEach Antibody binds to a Specific EpitopeMajor Antibody Types and their functions IgM9first to be made, good opsonizer and complement fixer IgA 9 Found in secretions: mucous and milk IgG9most abundant in blood, goes to fetus, good opsonizer and OK complement fixer, helps NK cells kill IgE9 Causes allergies, hypersensitivities and anaphylactic shock; Defends against parasitesMechanism of Antibody ActionComplement Protein-Ab interaction Results in Cell Lysis1stand 2ndExposures to a Specific AntigenT Lymphocytes (T-Cells) in bone marrow Multiply & mature in thymus gland (takes 2-3 days to become immunocompetent)

9 That bind to self-antigens are destroyed to and concentrate in lymphatic of T-cells Killer T-cells, helper T-cells, memory cells, suppressor T-cells Development of Lymphocytes Returns tissue fluid that has escaped the circulatory system back to the blood Lymph nodes filter out antigens from the lymph fluid Lymphocytes concentrate/reproduce in the lymph nodes, especially during infections Lymphatic SystemLymph Node: Filters LymphKiller T-Cell Activation Pre-killer T-Cell binds to target secreted by Helper T-Cell secretes cytokines after interacting with AP (macrophage)Cytotoxic T-Cell inducing Apoptosis in Target Cell The binding of a Cytotoxic T-cell to the Specific receptor molecules in a target cell may activate processes that lead to apoptosis: programmed cell T-Cell Lysing a Cell by Secreting PerforinAnimation of Cytotoxic T-Cell Lysing a ImmunityActive Immunity Naturally acquired during infections.

10 How? Artificially acquired by vaccines Vaccines contain dead or attenuated (weakened) organisms that stimulate the immune response Booster needed?Humoral and Cell-mediated ImmunityPassive ImmunityPassive Immunity Antibodies obtained from outside source Effect is short term (2-3 weeks) why? Examples Via placenta and mother s milk Via injections: Gamma globulin Anti-venoms Anti-toxins (botulism, rabies, tetanus)Disorders of the immune (Hypersensitivities) immune Response against harmlessantigenscalled Allergens Results in damage to various body Types of Allergies Immediate or Acute Hypersensitivity Most common; Localized Reaction in Seconds Plasma cells releaseIgEin response to allergen IgEstimulates mast cells to release histamine Blood vessels dilate and leak, Runny nose, watery eyes, itching, hivesAllergic stimulates Ab production (humoral immunity) binds to and sensitizes mast of allergen to mast cell stimulates release of results in inflammatory responseDisorders of the immune System (cont.)


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