Lesson: Fighting Back!Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Educational Standards :
Pre-Req Knowledge (Return to Contents)
Lesson 1 would be useful in order to introduce the space aspect of this lesson, and Lesson 5 (or previous knowledge of the functions of blood).
Learning Objectives (Return to Contents)
After this lesson, students should be able to:
Introduction/Motivation (Return to Contents)
Did you know that inside your body you have a tiny army that protects you from invaders? This is your immune system. Millions of bacteria, viruses, toxins and parasites try and penetrate your body's security system every day. This is demonstrated through the speed with which an animal decomposes once it has died and its immune system is no longer protecting it. When you become sick, your body is not able to do everything that it can when it is healthy. Mechanical damage (a broken bone, a torn ligament, etc.), vitamin deficiency (e.g., anemia if you do not get enough iron), organ decay, genetic disease, and cancer are all examples of when your body is "sick." By learning about the immune system, you will understand how your body protects itself and in what ways it can fail. Food poisoning, an inflamed/infected cut, and the flu are all examples of when your immune system allows a germ or toxins to get into your body. Luckily, the immune system is a fast learner and will ultimately search out and destroy this intruder (otherwise you would be sick for the rest of your life!). There are other times when your immune system makes a mistake and ends up attacking harmless cells. This is why some people have allergies or reject an organ transplant.
The immune system is the group of organs and tissues that protects the human body from outside germs and harmful things. It acts as a defense against foreign particles that want to enter your body, protects against some poisons, and suppresses cancer cells. Your immune system includes things such as your skin, tears, saliva and mucus — basically your first line of defense that blocks germs from entering the body. Tears, saliva and mucus keep germs from entering the body though the eyes, mouth and nose. Inside the body, the major components of the immune system are the thymus, spleen, lymph system, bone marrow, white blood cells, antibodies, complement system and hormones.
Bacteria and viruses are some of they body's biggest trouble makers. Bacteria are independent little creatures that roam around inside your body while viruses invade your healthy cells to multiply since they are not actually alive. Vaccinations and antibiotics are developed by chemical engineers to help your immune system fight some of the nastier germs. They have also created (and improved upon existing) cleaning agents and disinfectants to help kill germs in your house before they invade your body. Medical professionals use sterilizing equipment to ensure their utensils and "tools of the trade" are clean and will not give their patient an infection. And, environmental engineers work on keeping the air that we breathe and the water that we drink free of toxins (e.g., air purifiers and water filters). Without the advancements of our water and air systems by environmental engineers, we could become dangerously sick from breathing poor air and using/drinking inferior water.
What happens in outer space to astronauts' immune systems? Is the immune system affected by spaceflight? Yes, spaceflight definitely has an affect on the immune system — although engineers are still searching for answers as to what really causes this disturbance to the body. One of the reasons they have found is stress. Astronauts' stress levels tend to rise during spaceflight because of difficulty in adapting to microgravity, the risks involved with spaceflight, isolation from friends and family, close living quarters, sleep deprivation, the absence of a day and night cycle, busy work schedules, etc. Remaining in a state of stress for long periods of time can affect the immune system because the body deals with its current stress rather than with immunity (since it views it as a more immediate problem). This results in cuts taking longer to heal and colds lingering longer than usual due to the presence of stress. Immune suppression also makes astronauts more susceptible to common illnesses from bacteria and re-infections from viruses (such as cold sores). Another reason the immune system does not work as well in space could be the immune system's dependency on bone marrow. In space, astronauts lose bone mass (up to 2% per month) which could ultimately affect the production of the white blood cells, which help attack the body's invaders. Other variables that could affect the immune system are microgravity, radiation exposure, and other unknown factors.
Another problem astronauts encounter is the closed spacecraft environment, which increases the risk of spreading illness among the crewmembers. To minimize these risks, astronauts undergo immunizations and are quarantined for seven to ten days before launch (so that they are not exposed to as many germs as if they were out and about in public places). One way to evaluate how the immune system changes during spaceflight is to take blood samples from astronauts before and after a mission. Blood samples taken during spaceflight are not very accurate due to the fact that they would need to be frozen for later analysis (the equipment to analyze blood does not work in microgravity); however, refrigeration can kill cells or cause some of them to change their function. Urine and saliva — since neither has to be refrigerated — are used to measure the concentration of viruses during spaceflight. This information is then compared to the data collected before and after the mission to see if the number of viruses increases during spaceflight.
Engineers design the equipment used for collecting and measuring the immunity of astronauts. It is also an engineer's responsibility to make sure the astronauts have a designed environment in the spacecraft that keeps them as healthy as possible. There is still a lot of research that needs to be conducted before a longer mission (e.g., space flight to Mars) could be safely attempted. Today we are going to look more at the body's immune system and what engineers have done to help keep this system functioning and healthy.
Lesson Background & Concepts for Teachers (Return to Contents)
The immune system is the group of organs and tissues that protects the human body from outside biological influences. It acts as a defense against foreign pathogens (e.g., bacteria, viruses and parasites), protects against some poisons, and suppresses cancer cells. Bacteria and viruses (or germs) are the most common invaders. Bacteria are simple, completely independent, single-celled organisms that are able to eat and reproduce (you could think of them as fish swimming through your body). Bacteria can split into two in 20 to 30 minutes; therefore, one bacteria can become millions in only a few hours (see Figure 2). Viruses, on the other hand, are not really alive. They are simply DNA strands in a protective coating that use other cells to replicate. This hijacked cell either dies and bursts, freeing new virus particles, or splits off the viral particles (see Figure 3).
The immune system guards the body by recognizing objects that are supposed to be in the body (self) and those that are not supposed to be in the body (non-self). Once it has identified a harmful foreign or non-self agent, it launches an attack against it to remove it from the body. Problems can arise if the immune system is unable to distinguish between damaging non-self, harmless non-self, and self bodies. The immune system is divided into the innate immune system and the adaptive immune system. In other words, the immune system is programmed to recognize certain foreign bodies (e.g., various bacteria) while other times it has to learn to recognize them (this is how vaccinations work). Once your body has had certain diseases, it will rarely catch them again (e.g., chicken pox) because your body will recognize the virus and eliminate it before it can do anything to you. A vaccine is when a weakened form of a specific disease is injected into your body so that your immune system builds up and is able to defend against it (before you become infected with a stronger form of the disease). This only works with diseases that do not rapidly mutate or have many different strains (i.e., the common cold).
The first line of defense that the human body has includes the skin and mucus coatings, which line the openings in the body, such as airways. This lining provides a physical barrier to help block germs from entering the body. The skin secretes antibacterial substances that kill the bacteria that land on it — essentially, this keeps your body from growing mold overnight! Tears, saliva and mucus keep germs from entering the body though the eyes, mouth and nose (e.g., mucus traps dust to keep it from entering the lungs). Have you ever observed that if you blow your nose after being outside in high winds, you may notice a bit of dirt on your tissue? That dirt has been trapped by mucus before it enters your sinus cavity and causes harm to you. If a foreign body does penetrate this outer barrier, the immune system tries to detect and eliminate it before it can multiply. If it is able to reproduce and cause problems, it is the job of the immune system to destroy this threat.
Inside the body, the major components of the immune system are the thymus, spleen, lymph system, bone marrow, white blood cells, antibodies, complement system and hormones. The thymus is located in the chest next to the heart, as illustrated in Figure 4. It produces T-cells and is particularly important to babies as it keeps their immune system from collapsing.
The spleen filters the blood — looking for foreign cells and red blood cells that need to be replaced. If someone has their spleen removed due to illness or injury, they are at much higher risk of becoming ill in the future.
The lymph system extends throughout the body, similar to the way blood vessels do (except there is no pump, such as the heart, involved). Lymph — a clear watery fluid — oozes into the system and is naturally pushed through the body via muscle motion, carrying water and nutrients to cells. The lymph system filters lymph and removes bacteria. When fighting certain bacterial infections, the lymph nodes become swollen and you are actually able to feel them (usually in the neck). Tonsils, adenoids, Peyer's patches, and the appendix are all lymphoid tissues. Figure 5 illustrates the lymph node structure.
Your bone marrow produces new red and white blood cells. White blood cells (or leukocytes ) are arguably the most important element of the immune system. Lymphocytes are a type of white blood cell that circulates in the lymph and blood, searching for foreign bodies to destroy. These white blood cells handle most of the bacterial and viral infections the body encounters. They are divided into B-cells (mature in the bone marrow) and T-cells (mature in the thymus). B-cells secrete millions of antibodies (proteins that identify and neutralize foreign agents, such as bacteria and viruses) that mark foreign antigens for destruction by other immune cells. T-cells orchestrate, regulate and coordinate the overall immune response. T-cells trigger macrophages — cells that "eat" or engulf pathogens (agents that cause disease, such as viruses, parasites and bacteria), dead cells and cellular debris (see Figure 6). Human Immunodeficiency Virus (HIV) destroys T-cells, leaving the body extremely susceptible to opportunistic infections (caused by malnutrition, chemotherapy, etc.) that would not normally kill someone who was not infected with the virus. Acquired Immune Deficiency Syndrome (AIDS), a collection of symptoms and infections, is caused by HIV. Unfortunately, there is currently no cure for HIV or AIDS, and a person who has one or both of the diseases will eventually die; however, chemical engineers have discovered treatments for the two diseases and are striving to discover a cure in the future.
The complement system is a series of proteins that are produced by the liver. The complements work with the antibodies, causing infected cells to burst and then signal for that cell to be removed.
Several hormones are created by components of the immune system. Some hormones (tymosin) encourage lymphocyte production, while others (steroids and corticosteroids) suppress the immune system.
Sometimes the immune system is not able to keep up with the rapid rate of reproduction of certain types of bacteria. Antibiotics help out the immune system before the toxins that the bacteria produce can cause permanent damage. (Note: antibiotics only work on bacteria; they do not work on viruses, since viruses are not alive.) Chemical engineers have designed antibiotics to kill bacteria cells without affecting normal cells in the body (e.g., destroy the device in the bacteria that builds the cell wall). However, antibiotics can lose their effectiveness if the bacteria mutates into a new strain that differs from that which the medicine was not intended to destroy.
The immune system can also make mistakes. One example of an immune mistake is allergies — caused by the immune system reacting to an allergen (e.g., pollen, dust, animal fur, certain food, etc.) that should normally be ignored. Another problem is when the immune system attacks organ and tissue transplants. It does not recognize the tissue as "safe," and so it tries to get rid of it. Doctors try to avoid this problem by careful matching of the donor and recipient and by using immunosuppressing medicines — which can, however, sometimes lead to infection.
Vocabulary/Definitions (Return to Contents)
Associated Activities (Return to Contents)
Lesson Closure (Return to Contents)
What does the immune system do? It protects the human body from outside germs and harmful things. It is the group of organs and tissues that act as your body's defense against foreign particles that want to enter your body. Who remembers the immune systems first line of defense? This includes your skin, tears, saliva and mucus. Your body's attackers can include tiny bacteria and viruses. Which of these is alive? (Answer: bacteria) Bacteria are independent little creatures that roam around inside your body, while viruses invade your healthy cells to multiply since they are not actually alive.
How do engineers help our immune system stay healthy? Chemical engineers help develop vaccinations and antibiotics in order to help your immune system fight some of the nastier germs. Engineers also design cleaning agents and disinfectants to help kill germs in your house before they can invade your body. Environmental engineers work on keeping the air we breathe and the water we drink free of toxins (e.g., air purifiers and water filters). Engineers help design the systems to keep astronauts' immune systems healthy while traveling in space, including developing the instruments to monitor immunity throughout a space flight.
Basically, the immune system keeps all of your tissues and organs safe from germs and other foreign substances. It is important to take care of this system by eating a balanced diet, drinking plenty of fluids and getting a full night's rest.
Assessment (Return to Contents)
Discussion Question: Solicit, integrate and summarize student responses.
Brainstorming: As a class, have the students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Encourage wild ideas and discourage criticism of ideas. Have them raise their hands to respond. Write answers on the board. Ask the students:
Idea Web: Ask students to brainstorm a list of dangers to the body's immune system. (Possible examples may include: bacteria, viruses, broken bones, diseases, cancer, etc.) What effects do these dangers have on us and our environment? (Possible examples may include: symptoms of the flu or a cold.) What are possible solutions for reducing these types of dangers? (Examples may include washing our hands, sneezing into a tissue, vaccinations, antibiotics, etc.) Would any of these solutions be useful to astronauts in space? (Answers will vary by solutions.)
Lesson Summary Assessment
Send-a-Problem: Break students into teams of 2-3, and have them write their own questions about the immune system. Each student on a team creates a flashcard with a question on one side and the answer on the other. If the team cannot agree on an answer they should consult the teacher. Pass the flashcards to the next team. Each member of the team reads a flashcard, and everyone attempts to answer it. If they are right, they pass the card on to another team. If they feel they have another correct answer, they can write it answer on the back of the flashcard as an alternative answer. Once all teams have tested themselves on all the flashcards, clarify any questions.
Bingo: Provide each student with a sheet of paper containing a list of the following lesson vocabulary terms: immune system, virus, bacteria, antibodies, vaccine and chemical engineer. Have each student walk around the room and find a student who can define one vocabulary term. Have the students write down the definition on their paper. Students must find a different student for each word. When a student has all terms completed s/he shouts "Bingo!" Continue until two or three (or most) students have bingo. Ask the students who shouted "Bingo!" to give definitions of the vocabulary terms.
Lesson Extension Activities (Return to Contents)
Vaccinations are made from the bacteria or viruses that cause a disease. Have the students research common vaccinations and make recommendations for which vaccinations would be important for astronauts before they go into space. A good site for common childhood vaccines is: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5451-Immunizationa1.htm?s_cid=mm5451-Immunizationa1_e
Most of us have allergies. Allergies happen when the immune system attacks an object or chemical as if it were a germ. Have the students investigate allergies and how the immune system responds to them. What happens if an astronaut has an allergy in space? Are there methods for boosting the immune system to deal with allergies?
References (Return to Contents)
Bell, Trudy E. National Aeronautics and Space Administration, Space Research, The Office of Biological and Physical Research, Research and Projects, "In Sickness and in Health: Immunity and the Stressed Astronaut," March 2003, http://spaceresearch.nasa.gov/research_projects/immune_12-2002.html
National Institute of Allergy and Infectious Diseases, NIAID Net News, The Immune System, September 25, 2003, http://www.niaid.nih.gov/final/immun/immun.htm
National Institutes of Health, "In Their Own Words... NIH Researchers Recall the Early Years of AIDS," June 4, 2001, http://aidshistory.nih.gov/discovery_of_HIV/images/budding.gif
Oak Ridge National Laboratories, Review, Systems Biology: Advancing at a Breathtaking Pace, Volume 37 Number 3, 2004, http://www.ornl.gov/info/ornlreview/v37_3_04/images/a02_bacteria_full.jpg
U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Reader, January 6, 2006, 54(52);Q1-Q4 "Recommended Childhood and Adolescent Immunization Schedule – United States, 2006. Harmonized Childhood and Adolescent Immunization Schedule, 2006," http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5451-Immunizationa1.htm?s_cid=mm5451-Immunizationa1_e
Wein, Harrison. National Institute of Health, Word on Health, October 2000, "Stress and Disease," http://www.nih.gov/news/WordonHealth/oct2000/stressfigure.htm
Wikipedia, The Free Encyclopedia. "Immune System," http://en.wikipedia.org/wiki/Immune_system
Yaris, Lyn. Lawrence Berkeley National Laboratory, Currents, "Computers Identify T Cell Turn-Ons," edited by Pamela Patterson, October 3, 2003, http://www.lbl.gov/Publications/Currents/Archive/view-assets/Oct-03-2003/t-cell2.jpg
ContributorsTeresa Ellis, Denali Lander, Malinda Schaefer Zarske, Janet Yowell
Copyright© 2006 by Regents of the University of Colorado.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Acknowledgements (Return to Contents)
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.