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Unit 1: Cells and Systems Section 3: The Immune System I. The Immune System and Transmission of Infectious Diseases • The immune system attacks and destroys invaders that enter the body. • Pathogens are organisms or substances that cause disease (germs) • Antigens are any non-living substance that is foreign to the body and triggers an immune response (i.e., splinter, plant pollen, viruses) Diseases can be spread by: • Direct contact (shaking hands, sharing body fluids) • Indirect contact (sneezing, coughing) • Water and Food (eating foods or drinking water infected with pathogens) • Animal bites II. Fighting Infections a) 1st Line of Defense – Body prevents pathogens from infecting host Skin and linings of all internal organs • Sweat and oil (slightly acidic, preventing some pathogens from growing) • Gastric juice secreted by the lining of the stomach • Mucus and Cilia (line the nose preventing pathogens from entering respiratory system) Describe what each of the following “entry points” do to prevent entry of pathogens into the body: “Entry point” Entry blocked by… Eyes Tears, eyelashes Ears Ear wax Nose Mucus, cilia Mouth (and stomach) Gastric juice b) 2nd Line of Defense - Body mounts an immune response to an attack Two Types: • Innate Immune Response • Acquired Immune Response I) Innate Immune Response - general, non-specific (same for any invader) • fluid, cells and dissolved substances in the blood flow to the site of infection • this results in fever, swelling, and redness (inflammation) • white blood cells in the blood engulf intruders, destroying them – called PHAGOCYTOSIS https://www.youtube.com/watch?v=X-ubCIcAh4M II) Acquired Immune Response - more specific attack on a particular pathogen • Consists of 4 stages: 1. Recognition 2. Mobilization 3. Disposal 4. Immunity 1. Recognition • when body is invaded by a foreign substance, the body recognizes it as not belonging • The body uses white blood cells to recognize infection and to fight the invading disease-causing agent, or pathogen. • Phagocytes engulf (eat) the invading bacteria and signal Helper T cells to find B cells and tell them to produce antibodies. 2. Mobilization • B cells make antibodies, which bind to antigens to make them harmless or mark them for destruction by other white blood cells – Must have a perfect fit = lock and key – This can take time – this is why you can be sick for days/weeks. 3. Disposal • Once the right antibody that fits the antigen is found, they are mass produced and clump onto the invading pathogen, marking it for destruction. • Killer T cells kill the body’s own cells that have been invaded by pathogens, preventing the pathogen from reproducing in the cell and then infecting other cells. 4. Immunity • Some antibodies remain for future use – you usually cannot have the same disease twice! 3.2 Factors Affecting the Immune System I. Vaccinations • Vaccines are weakened pathogens given to people to protect them from getting a disease. • Vaccines stimulate your body to create antibodies to destroy the pathogen. • These antibodies will activate when the pathogen enters the body again. • Booster shots increase the antibody production and extend the immune system’s memory for that antigen. II. Disorders of the Immune System ALLERGIES: • An allergy is an unusually high sensitivity to a substance. • Any substance that causes an allergic reaction is called an allergen. • Side effects of an allergic reaction are a result of histamine. Histamine is a chemical that your body releases when you need to fight invaders. • Severe allergies can cause anaphylactic shock (swelling, breathing difficulties, and sometimes death). III. AIDS/HIV • Acquired Immunodeficiency Syndrome (AIDS) is an infection of the immune system that leads to health complications and often death. • AIDS is cause by the human immunodeficiency virus (HIV) that attacks the immune system by infecting Helper T-cells. • AIDS is transmitted by blood and semen. • There’s no cure for HIV/AIDS, but a variety of medications can be used in combination to control the virus. IV. Taking Care of your Immune System • Eat a well-balanced diet • Maintain personal hygiene (bathing, washing hands, brushing teeth) • Keep home clean • Avoid tobacco and other non-prescription drugs • Get plenty of rest and exercise • Keep vaccinations up to date • Do not engage in activities that involve sharing body fluids with others. 3.3 Epidemics and Pandemics • A disease is said to be endemic when it is at a constant, “normal” occurrence within a given geographical area. In this case, low numbers of people become sick. • A disease becomes an epidemic when it affects an unusual number of people in a community or region at the same time. A higher number of people become sick. Characteristics or an epidemic: – When the # of people infected rises above what is expected. – Illness is specific to a certain area. – Usually caused by circulation among people. Examples of Epidemics: • seasonal flu outbreaks happen each year • Norovirus outbreaks have occurred on cruise ships • in 2003, the severe acute respiratory syndrome (SARS) epidemic took the lives of nearly 800 people worldwide • in 2014, the Ebola virus resulted in 6070 deaths in West Africa Pandemics • A disease is a pandemic when it becomes prevalent throughout an entire country, continent, or the whole world. • Thousands to millions of people become sick. Characteristics of a pandemic: • • • • Causes serious illness. illness spreads easily from person. is an outbreak of global proportions. usually caused by a new form of a virus or bacteria. Examples of Pandemics: • Spanish flu killed 40-50 million people in 1918 • The Franco-Prussian War triggered a smallpox pandemic of 1870–1875 that claimed 500,000 lives • HIV/AIDS • In 2009, H1N1 How many people die from a pandemic depends upon: • The number of people who become infected • The severity of disease caused by the virus (its virulence) • The vulnerability of affected populations • The effectiveness of preventive steps The World Health Organization (WHO) provides an influenza pandemic alert system, with a scale ranging from Phase 1 (a low risk of a flu pandemic) to Phase 6 (a full-blown pandemic): • Phase 1: A virus in animals has caused no known infections in humans. • Phase 2: An animal flu virus has caused infection in humans. • Phase 3: Sporadic cases or small clusters of disease occur in humans. Human-to-human transmission, if any, is insufficient to cause community-level outbreaks. • Phase 4: The risk for a pandemic is greatly increased but not certain. • Phase 5: Spread of disease between humans is occurring in more than one country of one WHO region. • Phase 6: Community-level outbreaks are in at least one additional country in a different WHO region from phase 5. A global pandemic is under way. How to prevent the spread of diseases? • The best way to prevent a virus from becoming a pandemic is to get a vaccination. • Wash your hands often with soap and water. If these are not available, use an alcoholbased hand cleaner or gel sanitizer. If using a gel, rub your hands until they become dry. • Avoid touching your mouth, nose, or eyes with your hands unless you've just washed your hands. • When you cough or sneeze, cover your mouth and nose with a tissue. Then throw the tissue in the trash. Wash your hands afterward. • Avoid crowded places as much as you can and stay home if you show signs of illness. • Depending on the severity of the pandemic, consider wearing a face mask if you must go into a crowded area or be within 6 feet of others. • Consider wearing a face mask if you must come into close contact with an infected person.