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Grade 11A Name:______________________________ Class: _________________ Active reading 11A – Microbiology and Biotechnology Topic 3: Protecting against disease What is the body’s first line of defense? A pathogen is a microorganism, virus, or protein that can cause a disease. The body’s first defense against pathogens is two typical barriers that prevent pathogens from entering the body: the skin and mucous membranes. The skin is the first barriers. Oil makes the skin surface acidic and inhibits the growth of many pathogens. Sweat contains enzymes that kill bacteria. Mucous membranes are a second barrier. They cover internal body surfaces, such as the digestive, respiratory, and reproductive tracts. Mucous membranes produce a thick, sticky fluid, called mucus. Mucus traps pathogens before they can cause infection. What is the body’s second line of defense? Pathogens can sometimes cross the body’s physical barriers. When this occurs, the body responds with a second line of defense, called nonspecific immune responses. These responses, described in the table below, are general. That is, they occur in response to any type of invading pathogen. Therefore, the responses depend on the body’s ability to distinguish its own cells from invaders. Response Fever Protein activation Inflammation Description Body temperature often rises to fight a pathogen. High body temperature, or fever, is harmful to many bacterial pathogens. The body also produces proteins that attack pathogens. Complement proteins create holes in bacterial cell membranes. Proteins called interferones prevent viruses from functioning. An injury or infection in the body causes inflammation. During inflammation, chemicals and cells gather at the site of infection to destroy pathogens. See the diagram below Grade 11A Name:______________________________ Class: _________________ What is the body’s third line of defense? Pathogens have unique proteins, called antigens, on their surfaces. Antigens help the body identify pathogens as invaders. A macrophage is a white blood cell that ingests and destroys general pathogens. After a macrophage destroys a pathogen, it displays the pathogen’s antigens on its surface. This display alerts the immune system to an invader and activates the specific immune response. This response occurs when general responses fail and when a pathogen infects a cell. It involves white blood cells, or immune cells, that target particular pathogens. Immune cells have receptors that only recognize certain antigens. The shape of these receptors exactly matches the shape of specific antigens. As shown below, these receptors bind to antigens. Such binding produces many more specific white blood cells to fight the infection. Grade 11A Name:______________________________ Class: _________________ Key words Pathogen Nonspecific immune response Inflammation Macrophage Specific immune response Mucus A. Write one or more sentences to answer the following questions 1. What two physical barriers make up the first line of defense? _____________________________________________________________ _____________________________________________________________ 2. What is one way mucous membranes prevent infections? _____________________________________________________________ _____________________________________________________________ 3. What three defenses occur when a person breaths in a virus that crosses the mucous membranes in the respiratory tract? _____________________________________________________________ _____________________________________________________________ 4. Does fever only result from a bacterial infection? Explain your answer. _____________________________________________________________ _____________________________________________________________ 5. What does a macrophage do after it ingests a pathogen? _____________________________________________________________ _____________________________________________________________ Grade 11A Name:______________________________ Class: _________________ B. How are the nonspecific immune responses different from the specific immune responses? nonspecific immune responses Difference C. Complete the graphic organizer: The body’s second line of defense responses specific immune responses Grade 11A Name:______________________________ Class: _________________ D. Circle the letter of the phrase that best answers the question. 1. What does our body target as pathogens? a. b. c. d. all bacteria cancerous cells disease-causing bacteria microorganisms responsible for decay of dead material 2. What causes the production of interferons? a. b. c. d. bacteria chemicals viruses vaccines 3. An antigen is __________. a. a specific example of an antibody produced to eliminate a harmful microbe b. a white blood cell in your body that engulfs and eliminates foreign particles c. an organism or substance that creates a response by your immune system d. a type of chemical given as medicine to patients with allergies