Understanding the Immune System: Defenses Against Viruses and Bacteria, Slides of Botany and Agronomy

Download Understanding the Immune System: Defenses Against Viruses and Bacteria and more Slides Botany and Agronomy in PDF only on Docsity! Immune System Guarding against disease Docsity.com • You wake up one morning with a stuffy nose, slight fever, and fatigue. Do you have a cold or the flu? Or are they the same? • Should you go to your doctor for an antibiotic? Why or why not? W O R K T O G E T H E R Docsity.com Virus vs. Bacteria • Bacteria are living organisms that have a metabolism, have DNA, and can reproduce on their own. • Bacteria can be killed with antibiotics because these substances target key processes in bacteria, such as production of the bacterial cell wall. E. coli Streptococcus Docsity.com Body Defenses Docsity.com • Viruses and bacteria are everywhere. Some of them want to invade your body. How does your body defend itself against viruses and bacteria? W O R K T O G E T H E R Docsity.com Role of skin • Dead skin cells are constantly sloughed off, making it hard for invading bacteria to colonize. • Sweat and oils contain anti-microbial chemicals, including some antibiotics. Docsity.com Role of mucus and cilia • Mucus contains lysozymes, enzymes that destroy bacterial cell walls. • The normal flow of mucus washes bacteria and viruses off of mucus membranes. • Cilia in the respiratory tract move mucus out of the lungs to keep bacteria and viruses out. Docsity.com Role of phagocytes • Phagocytes are several types of white blood cells (including macrophages and neutrophils) that seek and destroy invaders. Some also destroy damaged body cells. • Phagocytes are attracted by an inflammatory response of damaged cells. Docsity.com (2) Wounded cells release chemicals that stimulate mast cells, @) Mast cells release histamine. . r @ Histamine increases capillary blood flow and permeability. ® Phagocytes leave capillaries and ingest bacteria and dead cells. Fever is caused by: 1 2 3 4 25% 25%25%25% 1. Toxins on the surface of viruses. 2. Release of histamines by damaged cells. 3. Your own body’s accumulated toxins. 4. Your body’s pyrogens signaling the hypothalamus. Docsity.com Based on what you know about non-specific defenses, what’s the best way to treat a cut in your skin? 1 2 3 33% 33%33% 1. Leave it exposed to open air. 2. Wash it, and cover it with a clean bandage. 3. Rub it with dirt. Docsity.com Major players • The major players in the immune system include: • Macrophage • T cells (helper, cytotoxic, memory) • B cells (plasma, memory) • Antibodies Docsity.com Some vocabulary: • Antibody: a protein produced by the human immune system to tag and destroy invasive microbes. • Antibiotic: various chemicals produced by certain soil microbes that are toxic to many bacteria. Some we use as medicines. • Antigen: any protein that our immune system uses to recognize “self” vs. “not self.” Docsity.com Antibodies • Antibodies are assembled out of protein chains. • There are many different chains that the immune system assembles in different ways to make different antibodies. Docsity.com Antigen recognition • Cells of the immune system are “trained” to recognize “self” proteins vs. “not self” proteins. • If an antigen (“not self”) protein is encountered by a macrophage, it will bring the protein to a helper T-cell for identification. • If the helper T-cell recognizes the protein as “not self,” it will launch an immune response. Docsity.com Helper T cells • Helper T-cells have receptors for recognizing antigens. If they are presented with an antigen, they release cytokines to stimulate B-cell division. • The helper T-cell is the key cell to signal an immune response. If helper T-cells are disabled, as they are in people with AIDS, the immune system will not respond. Docsity.com B cells • B-cells in general produce antibodies. Those with antibodies that bind with the invader’s antigen are stimulated to reproduce rapidly. • B-cells differentiate into either plasma cells or memory B-cells. Plasma cells rapidly produce antibodies. Memory cells retain the “memory” of the invader and remain ready to divide rapidly if an invasion occurs again. Docsity.com “Killer” T cells • While B-cells divide and differentiate, so do T-cells. • Some T-cells become cytotoxic, or “killer” T-cells. These T-cells seek out and destroy any antigens in the system, and destroy microbes “tagged” by antibodies. • Some cytotoxic T-cells can recognize and destroy cancer cells. Docsity.com Targets: invaders outside cells (viruses, Stimulates both humoral and cell-mediated Targets: defective body cells (infected cells, . bacteria, fungi, protists, toxins) immunity by releasing cytokines cancer cells), transplants Docsity .com Calling a halt • When the invader is destroyed, the helper T-cell calls a halt to the immune response. • Memory T-cells are formed, which can quickly divide and produce cytotoxic T- cells to quickly fight off the invader if it is encountered again in the future. Docsity.com • Why is it important for the immune system to have a way of stopping the immune response? Why not just keep going and fight off everything as it comes? W O R K T O G E T H E R Docsity.com Human Assist Docsity.com Helping the immune system • Medical science has created to systems for augmenting the human immune system: • Antibiotics (NOT the same as antibodies) • Vaccines Docsity.com Vaccine history • Variolation: The deliberate inoculation of people with secretions from smallpox (Variola) sores, by inhaling the dried secretions or rubbing them on broken skin. Used for centuries in Asia and Africa. Docsity.com Vaccine history • Vaccination: (From vacca, Latin for cow.) Invented by Edward Jenner in 1796. Jenner knew that dairy maids who had contracted cowpox never got smallpox. He inoculated a boy with secretions from cowpox sores, and showed the boy was immune to smallpox. Docsity.com Not that everyone accepted the process. Cartoons like this created widespread fear of the “cow pock” vaccine. Docsity.com True or false: Antibiotics weaken the immune system because your body doesn’t learn to make enough antibodies. 1 2 50%50% 1. True. Antibiotics are a type of antibody. 2. False. Antibiotics are not antibodies. Docsity.com True or false: Vaccines weaken the immune system because the body doesn’t learn to defend itself without help. 1 2 50%50% 1. True. The immune system needs to exercise itself or it won’t get strong. 2. False. Vaccination causes the body to learn to defend itself. Docsity.com Vaccines stimulate the production of: 1 2 3 4 25% 25%25%25% 1. Antibodies. 2. Helper T-cells. 3. Antigens. 4. Memory cells. Docsity.com But I caught a cold... again! • Because there are over 100 different known rhinoviruses, it’s possible to catch colds again and again. • In addition, cold viruses can mutate quickly. No sooner do we have immunity to one form than along comes another. Docsity.com How did I get this cold? • To catch a cold, a rhinovirus must reach the mucus membranes of your upper respiratory system. • Your hands pick up rhinoviruses from surfaces. Every time you touch your eyes or nose, or eat something with your hands, the viruses get a free ride. Like Mom said, wash your hands! • Viruses may also ride on re-circulated air, or reach you if someone sneezes right at you. Docsity.com Cold myths • Colds and “the flu” are different illnesses. Not every respiratory infection is “the flu.” • Colds are not caused by getting chilled. This belief comes from medical ideas of prior centuries, when it was believed that illness was caused by an imbalance of “humors,” and that a person with a cold actually had too much “coldness.” • “Feed a cold, starve a fever” also comes from prior centuries, when it was thought that people with a cold had too much “cold” and “moisture” in their bodies, and needed food to increase heat, while people with fever had too much “dryness” and “heat,” so needed less food to cool them down. Docsity.com Echinacea for colds? • Echinacea is supposed to “strengthen” the immune system. • Studies in petri dishes showed Echinacea stimulated white blood cells to produce more virus-killing peroxides, but controlled human trials have not had consistent results. Docsity.com Vitamin C for colds? • Vitamin C is necessary for making collagen, and for many body functions. • Absorption of Vitamin C increases during illness. It also has a very slight antihistamine effect. • Vitamin C won’t cure a cold, but may support some aspects of immune response. Docsity.com Zinc for colds? • Some studies have shown that moderate use of zinc lozenges slightly decreases the duration and severity of colds. • However, too much zinc can suppress the immune system, and can reach toxic levels. Zinc nasal sprays can destroy olfactory receptors. Docsity.com SV\IVSI A strands (a P Pa Ce ~ hybrid human-bird & Vv ; virus forms in pig and iia naa penile Docsity.com Flu Pandemic • The deadly 1918 flu pandemic has been recently identified as an avian flu. Unlike common flu, it killed mostly young, healthy people. • The recent H1N1 flu, mostly a swine flu, had many avian genetic markers similar to the 1918 flu. Docsity.com Allergies • Allergies are an immune system reaction to harmless antigens. • Some, such as pollen, may get in through the respiratory system. Fragments of food proteins may get through the digestive system. • The next time these proteins are encountered, the immune system attacks them. Docsity.com Cancer • Cancer occurs when the mechanisms that control cell division fail, and body cells divide out of control. • Cytotoxic T-cells can recognize and destroy these cells. But if division is too rapid, the T-cells cannot keep up. • Some cancer research involves assisting cytotoxic T-cells in recognizing and destroying cancer cells. Docsity.com AIDS • AIDS (Acquired Immune Deficiency Syndrome) is caused by an infection by the HIV (Human Immunodeficiency Virus), which attacks and destroys T-helper cells. Because it attacks the immune system directly, finding a vaccine has been difficult. • Some drugs can slow down HIV reproduction, but no cure exists yet. Prevention is still the best “cure.” Docsity.com AIDS The HIV virus fools helper T- cells into thinking its proteins are “self,” and so is able to infect the cells that trigger specific immunity. The virus forces T- cells to make more viruses, killing the T- cells when the new viruses burst out. Docsity.com Which cell does HIV attack? 1 2 3 4 25% 25%25%25% 1. Macrophage. 2. Red blood cell. 3. Helper T-cell. 4. B-Memory cell. Docsity.com If AIDS attacks specific immune defense, would a person with AIDS have a fever if they catch the flu? 1 2 50%50% 1. Yes. Fever is a non- specific response. 2. No. The entire immune system has been compromised. Docsity.com For some people, pollen allergies grow worse every year. Why? 1 2 3 4 25% 25%25%25%1. More pollen is produced every year. 2. Memory cells cause a stronger reaction. 3. Pollen evolves stronger toxins. 4. Suppressor T-cells become more active with time. Docsity.com