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Immune SystemWhat is the immune system? How does it protect your body?Why does your body get sick?How come when you get injured, that area tends to become red and feel warm?If microbes are everywhere, why aren’t we sick all the time?Bacteria thrives on your skin E.g. Staphylococcus and Streptococcus speciesBacteria colonizes your large intestines E.g. E. coliHow many grams of bacteria inhabit our bodies?What is the immune system?The body’s defense against disease causing organisms, malfunctioning cells, and foreign particlesIt is made up of networks of cells, tissues, and organsFirst Line of DefenceInnate or non-specific defense responses. Including:Skin TearsSalivaCilia and mucousGastric juice in your stomachSkinThe outer most layer of skin is made up of 20-30 layers of dead epithelial (skin) cells.Serves as a protective barrier against microbes (bacteria and viruses) and other foreign substances. 68961019367500TearsAka lacrimal secretionContinuously lubricates and cleanse eyesContains lysozyme – an enzyme that destroys bacteriaSalivaWhat’s the first thing you do when you cut your finger?Saliva contains many chemicals that break down bacteriaHowever, thousands of different types of bacteria can survive these chemicalsAlso contains lysozymeCilia and MucusCiliaPropel debris-laden mucus away from nasal cavity and lower respiratory passagesDirects them out of the bodyMucus68961032702500Traps microorganisms and foreign particles from respiratory and digestive tracts.Stomach AcidSwallowed bacteria are broken down by incredibly strong acids in the stomach What is this acid?Hydrochloric Acid (HCl)pH below 2 How does the stomach protect itself from the acid?RecapFirst Line of DefenseSkin TearsSalivaCilia and mucousGastric juice in your stomachActs as a barrier that prevents pathogens from entering the body. As long as pathogens stay outside the body this defensive line will handle things just fine.Second Line of Defense AKA innate or non-specific defense (immune) responses. Includes:White Blood Cells (macrophages and neutrophils)Inflammation FeverInterferonWhite Blood CellsMacrophages“Big eaters”Phagocytic – engulfs foreign particlesNeutrophilsMost abundant white blood cellPhagocytic – engulfs foreign particlesOnce engulfed, the phagocyte breaks the foreign particles apart in organelles called Lysosome.Note the difference between Lysosome and Lysozyme, they both break down foreign particles, but Lysosome is an organelle and Lysozyme is an enzyme. 38101168400034899601206500Inflammatory Response Is triggered whenever body tissues are injured.E.g. cuts, scrapes, bone fractures, infection, etc.Injured body cells release chemicals called histamines, which begin inflammatory responseHistamines are produced from basophils AND mast cells.8953520637500Inflammation4 classical symptoms:RednessSwellingHeatPain Main Events in Inflammation 1) Vasodilation – capillaries dilate to allow blood to flow to injured areaThis is responsible for the redness and heat.Allows WBCs flock to infected area like sharks to blood2) Dilated capillaries increase permeability, so fluid and cells are able to leak out, this causes swelling.FeverSystemic response to invading microorganismsAbnormally high body temperatures above 37oCPyrogens are chemicals released from macrophages, reach hypothalamus, and temperature rises (Pyro = Fire)What purpose does a fever serve? Viruses3089910461645…and after.00…and after.584835594995Cell before infection…00Cell before infection…Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells.InterferonVirus-infected body cells release interferon when an invasion occursInterferon – chemical that interferes with the ability of viruses to attack other body cellsWhat happens to already infected cells?AntigensAre substances that initiates the third line of defense and causes your immune system to produce antibodiesCould be any foreign substance from the environment137541027622500E.g. Chemicals, bacteria, viruses, pollen 3736975-63500Third Line of DefenseAdaptive or specific defense systemIncludes:Humoral ImmunityB lymphocytes production of antibodiesCell-Mediated ImmunityT lymphocytes Both B and T lymphocytes are produced in the bone marrow3 important aspects:1) It is specific2) It is systemic3) It has “memory”Takes longer to activate than non-specific responses.Humoral ImmunityAlso known as the antibody mediated immunityB lymphocytes mature in the bone marrowAre antibody producing cellsThese are called plasma cellsAntibodies are Y-shaped moleculesAntibody306133528130500Antibodies have receptors to bind to antigens3238523622000Cell mediated responseInvolves living cells as protective factorsThese cells are T lymphocytesRecognizes infected human cells and cancer cellsT lymphocytes will attack these infected cells, quickly kill them, and then continue to search for more cells to kill T lymphocytes mature in the thymus gland29946601968500Thymus GlandWhat is the function of the Thymus Gland?T LymphocytesDifferent types of T cellsTh – T helper cellsActivates all aspects of immune responseTc – cytotoxic T cells (killer T cells)Highly specific, kill abnormal cellsHelper T CellsPrimary task is to activate B cells and cytotoxic T cells.BUT they themselves must be activatedActivation of Helper T Cells48958515748000Activation of Cytotoxic T Cells33280351206500All nucleated cells present antigens that represent what's happening in the cellIf something is not right (presents non-self antigen), then the Cytotoxic T cells will detect this and kill the cellSecrete specialized proteins called perforins that poke holes in cell membrane and granzymes that tell the cell to kill itself. Note* require activation factors from an activated T helper cell to become activeActivation of B cells and production of plasma and memory cells. 817245113030003794760000Humoral Recapused to fight all threats Does so by the production of antibodies (AKA immunoglobulins) Antibodies serve several functions: Attract phagocytesComplement system activation (pokes holes in bacterial causing them to lyse) To neutralize certain toxins (example snake venom)Cell Mediated Recapused to fight intracellular pathogens or abnormal cellsDoes so by killing infected (virus, bacteria, parasite) cells or abnormal cells. Immunological MemoryPrimary Immune Response:First time the body encounters a particular antigenAntibodies detected in serum between 7-10 daysSecondary Immune Response:Upon re-exposure to the same antigen, the body’s immune response will be much faster, more effective and prolonged since memory cells have been made previously that target for these types of antigens specifically.Antibodies detected in the serum between 3-5 days.280035508000What is Immunity? Resistance to disease causing organism or harmful substanceTwo typesActive ImmunityPassive ImmunityActive ImmunityYOU produce the immune response! (e.g. antibodies)Your body has been exposed to the antigen in the past either through:Natural exposure (daily exposure to foreign particles)Artificial exposure (immunizations/vaccines)You fought it, you won, you remember itActive immunity develops slowly but lasts for years.4109085698500Passive ImmunityYou DON’T produce the immune response directlyPre-made antibody molecules enter the bodyImmediate effectShort duration (2 weeks to 1 month)Natural (A mother will pass antibodies on to her baby during pregnancy)Through what organ? Artificial (antibody produced in another host injected. E.g. anti venom)How long does active immunity last?It depends on the antigen Some disease-causing bacteria and viruses mutate into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shot Booster shot - reminds the immune system of the antigenR0Known as a the basic reproduction number Expected number of cases directly generated by one case in a population (ie. How many people will one person infect) If R0 > 1 then the number of cases is growingIf R0 < 1 then the number of cases is decliningHerd Immunity272796062200the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination.Measles, the most contagious virus on earth, needs to have as much as 95% of a population immunized in order to have a R0 < 1Think the flu is no big deal?In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globeIt infected ~one third of the human population and killed ~100 million people (5% of population)3547110762000HIVHIV stands for Human Immunodeficiency VirusIt is found in blood, semen, and vaginal secretions. The virus commonly enters the body through blood transfusions or blood-contaminated needles and during sexual intercourse. HIV attacks the helper T cells of the immune systemTherefore, activation of B lymphocytes and cytotoxic T cells cannot occur.HIV doesn’t kill you – it cripples your immune systemAIDSAIDS stands for Acquired Immune Deficiency SyndromeIt is caused by HIVDiseases your immune system can normally defeat now becomes life-threatening The first symptoms of AIDS are similar to those of a cold. Self and Non-selfOur immune system has an incredible ability to recognize our cells as “self” and foreign cells as “non-self”Our own cells carry distinctive “self” marker molecules that tell the immune system to leave those cells alone and to not destroy them. Recall, foreign “non-self” cells that are capable of triggering an immune an TransplantsCells and tissues from another person carries their own self markers and therefore, will be recognized as “non-self” in our bodies.This is the reason why some organ transplants are rejected and unsuccessful.There are 4 major types of transplants called grafts:Autografts – tissue grafts transplanted from one body site to another from the same person.Isografts – graft from a genetically identical individual. E.g. identical twinAllografts – grafts from the same species but not from a genetically identical individualXenografts – grafts from animals34232851206500Autoimmune DiseasesResults when the body’s immune system fails to recognize its own body cells It launches an attack against its own cells thinking that they are foreign antigensExamples of autoimmune diseases are rheumatoid arthritis and type 1 diabetes.These diseases cannot be cured, they can only be treated to relieve symptoms and prevent long-term damageAllergiesImmune system forms an improper immune response to harmless foreign particles causes sneezing, runny nose, and watery eyesAnti-histamines block effect of histamines and bring relief to allergy sufferers 61341030226000Lymphatic SystemThe lymphatic system is a major part of the immune systemIt is made up ofLymphatic vesselsLymph nodesLymph 2604135952500Lymphatic VesselsLymphatic vessels consists of blind-ended tubes which carries lymph in one direction – only towards the heart. Lymph is made up of the fluid leaked from blood(lymph = clear water)Pathogens and cancer cells may spread throughout the body via the lymphatic streamLymphoid CellsLymphoid cells include lymphocytes, plasma cells and macrophages.Lymph NodesSignificant lymphoid organFunction:Filter lymph – by using macrophages to remove and destroy microorganisms and other debrisTo help activate the immune system – high density of immune cellsOther Lymphoid Organs39185851206500Spleen Largest lymphoid organFunction:Destroys old and defective red blood cellsHigh density of immune cells (lymph node of the “blood”) ThymusMost active during early years of life.Function:Site of T lymphocyte maturationTonsilsSimplest lymphoid organFunction:Gather and remove many of the pathogens entering the pharynx in food or in inhaled air. Functions of lymphatic system recapBody fluid balance – takes up excess fluids in tissuesImmune – has sites of high immune cell density (nodes) which “sample” body for pathogens Fat transport – transports absorbed fats from S.I. into blood circulation ................
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