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The Immune System The Immune System (p.382-386) • a collection of cells and tissues that defend the body against *pathogens that gain entry. The major parts include: – white blood cells (lymphocytes ie.B-cells &T-cells, macrophages) – lymphatic system (lymph, lymph vessels, nodes) – blood (circulatory system) – spleen – thymus gland – bone marrow pathogens -> any disease-causing agent eg. bacteria, viruses, fungi, parasites. • We keep pathogens from taking over our bodies and causing disease through: • I. Non-specific defences • II. Specific defences I. Non-specific defences • guard against wide variety of pathogens, regardless of their cause (general). • effectiveness does not depend on prior exposure • Two Types: – A. First line – B. Second line A. First line of defence: (physical and chemical barriers) 1. Skin • protective layer - prevents entry on most of the body • Inhospitable (dry and contains indigestible keratin) • constantly shedding old cells- gets rid of pathogens that may be growing • oil (containing bactericide) and sweat glands – produces acidic environment: hard for microorganisms to grow • burn victims - open to infections - why? 1st Line cont’d 2. Mucus, hairs and cilia • Mucus - found in digestive and respiratory tracts • mucus is wet and sticky, traps dirt and pathogens in the trachea and digestive tract • Cilia - hair-like structures that grow in the lining of the respiratory tract; they wave mucus upward to the throat where it is coughed up, sneezed out or swallowed to the stomach 1st Line cont’d 3. Acids and digestive enzymes (chemical) • acids in the stomach (hydrochloric acid ) kills most bacteria 4. Secretions of the body • eg. tears, saliva, nasal secretions • contain lysozymes, which break down the cell walls of bacteria (killing them and preventing reproduction) 1st Line cont’d 5. Urine • flushes out unwanted pathogens by filtering waste from the blood in the kidneys B. Second line of defence: (still a non-specific defence) 1. The inflammatory response • damaged cells release chemicals (eg. histamine) Histamine causes: • blood vessel dilation (increases blood flow (redness) and temperature). May be enough to destroy/neutralize some pathogens • Capillaries to be more porous, allowing tissue fluid to gather in the area (swelling) • soreness 2nd line cont’d… 2. Fever • macrophages, after engulfing (eating) pathogens, secrete chemicals that produce a fever • the body raises its thermostat; the higher temperature kills pathogens (ok to a certain point - why? 2nd line cont’d… 3. Use of Phagocytosis • cells that kill bacteria by ingesting them • (i) macrophages -> phagocytic cells found in liver, spleen, brain and lungs. They circulate in the bloodstream and tissue fluid, looking for pathogens to engulf • (ii) neutrophils and monocytes -> white blood cells that attack bacteria – dead macrophages and bacteria are visible as pus at the site of infection http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter22/animation__the_immune_response.html II. Specific defence (third line of defence) • i.e., the immune response • The body produces *immunity by the production of **antibodies to destroy the pathogen. • The first encounter with the pathogen results in the creation of the immunity and is called the primary immune response. • Should the pathogen enter the body a second time, the body reacts with the secondary immune response, which is faster acting and the person displays fewer symptoms. • * immunity -> the ability of the body to resist disease, after being exposed to it in the past. • **antibodies -> a Y-shaped protein formed in response to a virus or other foreign substance in the blood or tissues. (p.384 Fig.11-27) Immunity may be active or passive. Active Immunity • long lasting (years) • body is exposed to pathogen, goes through the specific immune response and develops an immunity against the pathogen • eg. accidental exposure (chicken pox), vaccines • vaccine - injecting dead/weakened pathogens into the system, causing an immune response • If the person is later exposed to the ‘actual’ (stronger) pathogen they will either not get ill or not as ill, as they would’ve without the vaccine. • eg. whooping cough, mumps, polio, measles and chicken pox https://www.youtube.com/watch?v=B_hCLWtEHL8 – How anti-vaxxers sound to normal people https://www.youtube.com/watch?v=nDjz5qHIzsc - If Anti-Vaccine Parents Rode The Magic School Bus Passive Immunity • is temporary (usually lasting only a few months) • immunities passed on from one person to another • eg. pregnant mother passes on immunities to unborn child through the placenta and to a newborn through breastfeeding. • Breastfeeding prolongs the passive immunity (makes it longer lasting) May 26 Review: • Cell-mediated immune response http://www.youtube.com/watch?v=1tBOmG0QMbA&safety_mode=true&persist_ safety_mode=1&safe=active • Antibody mediated immune response http://www.youtube.com/watch?v=hQmaPwP0KRI&safety_mode=true&persist_safety _mode=1&safe=active AIDS - p. 124 & 496 • Acquired Immune Deficiency Syndrome (disease) – caused by the Human Immunodeficiency Virus • HIV is a retrovirus; i.e., it has RNA as its nucleic acid (genetic material) instead of DNA How does HIV cause AIDS? • HIV attacks helper T-cells. • They move into the nuclei and may remain dormant (inactive) for up to 10 years. Thus you may have the virus but not the disease. • Once the virus becomes active, it uses the DNA machinery in the host’s nucleus to replicate itself. • The many viruses then leave the helper T-cells (now destroyed), to infect other helper T-cells and macrophages. • Results in a weakened immune system, making the body vulnerable to many diseases. • AIDS victims often die of pneumonia or rare cancers. • HIV is difficult to make a vaccine for since: – it mutates quickly, so that a vaccine is no longer effective – it can stick helper T-cells together and so move from cell to cell without having to deal with antibodies in the blood or tissue fluid – there are millions of strains (versions) of the virus) AIDS is spread through: • 1. Direct contact with bodily fluids – semen (through sexual contact) & vaginal fluid – blood (cuts, transfusions) • 2. Sharing of contaminated hypodermic needles • 3. From mother to child (through the placenta) or during birth AIDS can be prevented by: • Avoiding sexual contact with infected individuals (using latex condoms and spermicides) • Avoid blood transfusions with infected individuals (since 1985 blood is screened through testing) There is no cure! • There are treatments – a wide variety of drugs often administered together (cocktail) • Do questions: p.386 #1,2,3,5,6,7; P.388-89 #24,25,31,36,39,41 Immune System Malfunctions 1. Autoimmune Diseases/Disorders (p.386) • when T-cells or antibodies mistakenly attack the body’s own tissues as if they had foreign antigens; cause is unknown • Often inherited; some start after recovery from an infection or injury • can be very serious and debilitating • eg: (a) multiple sclerosis -> body attacks the myelin covering of nerves (b) lupus -> disease of 1000 faces (varied symptoms) • • • • (c) rheumatoid arthritis -> inflammation of the lining of the joints continues into bone, cartilage, tendons and ligaments causes pain, stiffness, fever, swelling, fatigue, and loss of appetite. • Treatment may include (1) non-steroidal antiinflammatory drugs, (NSAID’s) to reduce pain and inflammation, (2) aspirin, (3) steroids, or (4) corticosteroids. • commonly affected joints are wrists, knuckles, elbows, shoulders, feet, ankles, hips, knees. 2. Allergies • An allergy is an exaggerated response by the immune system to a harmless material such as pollen, mould, or cat (animal) dander. Two types of allergic reactions are: • immediate (acute) – – – – *most common occurs within seconds of exposure to allergen usually disappears within 30 min. specialized antibodies can cause watery eyes and runny nose. They can trigger certain cells to release histamines causing swelling and redness. – some forms of asthma are acute reactions to inhaled allergens which then trigger a massive release of histamines, setting off spasms of the bronchioles • Delayed – less common – several exposures results in an allergic reaction buildup over time – Food allergies can trigger vomiting, cramps and diarrhea – Most allergies can be treated with antihistamines. – more severe - Epi pen Extra Info if you want/need review The Lymphatic System - p. 322-323; Fig. 9.24 & 9.25 • The lymphatic system consists of: – (a) lymph vessels - similar to veins in that they have valves that help direct the lymph forward (no pump!) – (b) lymph - contains tissue fluid (water, salts, gases, chemicals, hormones) and white blood cells but no red blood cells – (c) lymph nodes - swellings found at various places in the body where white blood cells gather pathogens to destroy them Functions • 1. Combats disease by collecting harmful microorganisms (pathogens), filtering them from the blood and bringing them to lymph nodes (Immune) • 2. Siphons off excess fluid from around body cells and dumping in back into the thoracic duct located just superior (above) to the heart (circulatory) • 3. Absorbs fatty acids and glycerol into lacteals in the villi of the small intestine (digestive) and dumps it back into the circulatory system . The primary immune response Four phases: 1. Invader identification • macrophages engulf pathogens and display pathogen *antigens on their cell membranes • helper **T-cells bind to the antigens, triggering the release of a chemical signal for other helper T-cells to clone * antigens -> any substance that causes an immune response. Viruses and microorganisms have substances on their outer surface that are antigens; eg. of antigens: proteins, carbohydrates, nucleic acids ** T-cells mature in the thymus gland (found in your chest) The primary immune response Four phases: 2. Cloning phase • helper T-cells clone (divide to make many) and stimulates killer T-cells (also called cytotoxic T cells) and *B-cells to clone also. * B-cells mature in the bone marrow The primary immune response Four phases: 3. Attack phase • B-cells produce antibodies • They bind to the antigen on the pathogen, causing them to clump together in bunches • Now they’re ready for the macrophages to engulf them • Antibodies (Y-shaped) may be attached to the Bcell membranes or allowed to float in the blood plasma, lymph or tissue fluid, ready to tag pathogens. The primary immune response Four phases: • T-cells may bind to the B-cell antibody-antigen complex, activating the B-cell. • This causes the B-cell to enlarge and divide, producing plasma cells and memory cells. • Plasma cells produce large amounts of the same kind of antibodies carried by the B-cells. • When the danger has passed, plasma cells undergo apoptosis (which means programmed cell death). The primary immune response Four phases: • cytotoxic T-cells puncture diseased cell membranes causing the pathogens to flow out while macrophages lie ready to engulf them. • Cytotoxic T-cells attack cells that are being infected by bacteria or viruses and cancer cells. • The attack continues until the disease is brought under control. The primary immune response Four phases: 4. Slowdown / Memory phase (a) Slowdown • suppressor T-cells slow down the cloning until the numbers of helper • T-cells, B-cells, and cytotoxic T-cells are back to normal (b) Memory • special memory B-cells and cytotoxic T-cells remember that pathogen should it come again. • The body has developed an immunity against that pathogen. • If exposed to it a second time, the memory cells will quickly produce the antibodies to destroy them. • This is the secondary immune response. • Note: Refer to handouts on the primary and secondary immune responses and Immune Response • Immune System, White Blood Cells, T-Cells, Cancer Cells 2:50 http://www.youtube.com/watch?v=an6NrTgCDFQ&safety _mode=true&persist_safety_mode=1&safe=active • Immune System - Natural Killer Cell - The Formulation 3:01 http://www.youtube.com/watch?v=z3a3AKhIb0&safety_mode=true&persist_safety_mode=1&safe= active