Introduction
Why It Matters
How We Find Out
Story Time
Common Hazards: Sunburn
Common Hazards: AIDS/HIV
Activities
Self-Study Game
Introduction
This module will help you understand how your body reacts to such invasions and what you can do to help your bodily defenses.
Objectives
After completing this lesson, each student should be able to:- Explain how the skin acts provides protection to underlying tissues from infection and disease.
- Describe what the lymphatic system is and what it does.
- Explain the principles of vaccination and the different types of immunity that it can confer.
- Summarize the hazardous nature of sunburn and of AIDS.
Why It Matters
Defense mechanisms fall into two categories:
- Keep the germs out of the body (that is what skin does)
- Fight the germs once they get inside the body (that is what the immune system does)
Vaccines & Disease
When your grandparents were children, a disease called polio was causing hundreds of thousands of children to be crippled for life, as their muscle cells were destroyed by the virus. Some children had to live inside an “iron lung” that breathed for them because their chest muscles were dead and they were unable to breathe on their own. During the 1950’s, this frightening disease was stopped, however, because of the polio vaccine. (View more about polio.)Another major disease, smallpox, raged for hundreds of years in all parts of the world. The disease was so common and deadly that a worldwide campaign to eliminate it began when a vaccine was developed. The vaccine left a scar on the skin, but it was worth it to prevent smallpox. Because so many people around the world were vaccinated, the disease has apparently disappeared. No reports of smallpox have appeared since 1979, when it was declared to be eradicated. (Access more information about the role of vaccination in eradicating smallpox.)
Of course, we don’t always have vaccines that work against some diseases. Throughout this unit, we will learn how the body fights diseases both with and without the help of vaccines. We will introduce the structures and functions involved in bodily defenses that keep you safe and healthy.
How We Find Out
Many teenagers have a frustrating time dealing with the little bumps on their face called “pimples”. Instead of focusing on how to treat them, let’s discuss why the small pustules (zits) typically appear as white bumps.
Why are they white? It is because of the white blood cells (see the photo of a white blood cell on the right). If you smeared the pustule on a glass slide, stained the slide, and looked at it under a microscope you would actually be able to see the white blood cells! The white blood cells are attracted to bacteria under your skin. Why?
Remember the description of a splinter from the introduction to the unit? The splinter and the bacteria on it crossed the first line of defense, the skin. The second line of defense is the white blood cells. White blood cells are attracted to wounds or areas where bacteria has injured the skin. The white blood cells become concentrated in an area, as they block bacteria from entering surrounding tissues. Your first and second lines of defense, the skin and immune system, work together to keep your body healthy and free from infection.
Why do white cells gather at the site of injury? There must be some kind of signal to attract them to leave the blood and to gather at the injury site. Likewise, it seems natural to suspect that the white blood cells have something in them that neutralizes or destroys bacteria. How can we learn about the ways in which white blood cells protect us from infection?
Story Time
Peter Medawar, 1915-1987
Even in 1915, it was a small world for Peter Medawar. Peter’s father was from Lebanon, but moved to England to seek his fortune and marry an Englishwoman. He did marry and after their marriage, the couple moved to Rio de Janeiro, Brazil, where Peter’s father became a salesman for a dental supply company out of England. Peter was born in Rio, but nonetheless was declared a citizen of England.Childhood Interests
Before entering school, Peter Medawar learned Portuguese, the first language of Brazil, because school was taught in that language. He recalls of his mathematics teacher that she “considered it her business to teach us addition, subtraction, and the like, and she jolly well did.”
A main childhood interest of Peter was reading comic books. He and his brother had quite a collection. Another perhaps surprising interest was opera. Peter fell in love with the gramophone, the forerunner of today’s record player or CD player. Due to the kinds of music his parents played in the house, he acquired a love for opera, even as a child. He would save his pocket money for weeks in order to buy a record. He enjoyed pretending to be an orchestra conductor in front of a mirror.
Most of Peter’s free time as a child was spent with his brother on Copacabana Beach. He marvels that he did not catch polio, which afflicted many children in his neighborhood. His very own brother was crippled for life by the disease. Peter recalls how the town’s sewers emptied directly onto the beach, and the children played around huge stagnant pools of sewage.
Common Hazards: Sunburn
Sunburn
Overview:
What happens when the sun hits your skin? Either you get tanned or you get burned. Why do some people tan while other people burn? How does sunscreen help? What happens when you have prolonged exposure to the sun? What the sun does to your skin is very important because the skin is your first line of defense!
What the sun does to your skin:
Sunburn is caused by ultraviolet light from the sun. These rays activate melanin, which is the body’s protective pigment against the sun, and turn the melanin brown. This creates a tan. Radiation has to hit something in order to dissipate its energy. Melanin provides target molecules that safely absorb radiation energy. However, sometimes the body can’t handle the amount of rays that the sun is giving off. In this case, the sun will actually burn the skin – a sunburn!
What causes your skin to be red from a sunburn?
Everyone knows that you get a sunburn from being outside too long.
What is happening under your skin to allow you to burn?
Don’t confuse a sunburn with a burn that you will get from a fire, because they are different. 
The red color is partly because of increased blood flow to the injured area. When cells’ membranes are damaged, certain chemicals leak out. Two of these are histamine and bradykinin, which are peptides that cause the blood vessels to dilate. As we have learned, this reaction is common when a part of the body has been injured. Also, the body will begin certain inflammatory processes, which causes the pain and soreness felt as your body attempts to heal itself. When a burn is severe, you can actually have blisters, caused by the movement of protective cells in the blood to the extremely injured areas.
What happens when you have prolonged exposure to the sun?
Unfortunately, skin cancer can develop from being in the sun too much. When you burn, you are causing damage and death to cells. This injury can cause damage to your DNA, which is very serious! 
This DNA damage sometimes can cause painless patches or lumps to form. These skin formations are cancer. The most common form of skin cancer is the most dangerous, melanoma. The word melanoma means that melanin in the body has become cancerous. If skin cancer is caught early, you have a good chance of survival and complete recovery. The common treatment for skin cancer in the early stages is removal of the cancerous area. However, in further stages, chemotherapy and radiation may be used. The use of radiation may seem weird because that is what caused the cancer in the first place, right? Well, the radiation received at the doctor’s office is actually a very strong dose, so that it kills or disables the cancerous cells. To prevent all of this, you must reduce the amount of sun that is absorbed by your tissues.
How can sunscreen prevent a sunburn?
Sunscreen can not only prevent a sunburn, it can greatly reduce your chances of getting skin cancer from the sun. When you look at a bottle of sunscreen, you will see a number, called the SPF, or sun protection factor. This number, which varies according to the strength of the sunscreen you need, is actually a number you can use to find out how many minutes you can stay in the sun without being burned. If you are normally okay in the sun for 10 minutes and you use a lotion with a SPF of 10, then you would be okay in the sun for 100 minutes!Why do some races of people burn more easily than others?
Certain races have a higher concentration of melanin in their skin than others. For example, a light-skinned Caucasian may have only 1-3% melanin in their skin, whereas a darker-skinned African may have as much as 43%. That is a big difference!Conclusion
The sun is a powerful enemy of the body’s first line of defense, the skin. Prolonged exposure to the sun can cause a painful sunburn or even skin cancer! So before you head outside next time, make sure that you apply sunscreen that is strong enough to protect you! For further information, take a look at these websites:http://sunguardman.org/index.php
http://www.aad.org/public/publications/pamphlets/sun_sunprotection.html
www.hooah4health.com/4life/hooah4kids/kidssun.htm
To look up a current UV report on a map of the United States:
Intellicast.com
What are some other dangers to your bodily defenses?
Common Hazards: AIDS/HIV
AIDS/HIV
Overview
AIDS is a fatal disease. The best way to combat the disease is knowledge about how to prevent it. There is not a cure nor a vaccine.What is AIDS?
We need to start with a couple of acronyms and their definitions:- AIDS- acquired immunodeficiency syndrome
- HIV- human immunodeficiency virus.
How do you get AIDS?
HIV can be contracted a variety of different ways. However, 97% of all cases can be traced to one of three routes:- sexual intercourse
- contact with body fluids, especially blood ( blood transfusion, needle sharing)
- mother to fetus transmission.
Why is AIDS so bad?
As discussed earlier, AIDS/HIV causes the immune system to no longer function. HIV causes people to become sick with infections that normally wouldn’t affect them. Diseases like cancer and pneumonia can set in. These diseases are called opportunistic diseases because they invade after the immune system has been compromised. Although the HIV virus itself can cause some flu-like symptoms, it is actually the opportunistic diseases that kill AIDS victims.How is AIDS treated?
Currently there is no cure or vaccination for the HIV virus. Doctors will prescribe a variety of medicines, including antiviral drugs (those that destroy viruses) and immunomodulator drugs (those that increase the effects of the immune system). However, most drugs are used to treat the symptoms, not the cause. While drugs will prolong the life of the patient, it will not cure them.Where is AIDS most prevalent?
AIDS has reached epidemic proportions in several areas of the world. However, Africa has been the center of the crisis since the beginning. The sub-Saharan Africa is the area of the world with the greatest prevalence of AIDS, followed by southeast Asia. Several relief projects are underway to give these people medicine and treatment.Conclusion
Although AIDS is more widespread than ever before, medicine is providing the public with more answers. We now know how it is transmitted and how we can prevent the disease. Armed with this knowledge, hopefully people will protect themselves and we can hold the epidemic in check until there is a vaccine or a cure for the disease. To find out more information concerning AIDS and the HIV virus, check out these websites:www.aacap.org/publications/factsfam/aids.htm
www.sfaf.org/aids101/
http://www.aidsinfo.nih.gov/
www.projectinform.org/
Activities
Activity One: Skin absorption
Orientation:
This activity will focus on the first line of bodily defense: the skin! Students will complete observations and answer questions about their own skin as well as the skin of others. They will complete an experiment to examine the absorption of certain materials on the skin.
Materials:
Eye dropper, water, hand lotion, mineral oil, rubbing alcohol
Student Observation Journal for Activity #1 (right mouse click and select “open in a new window” to open as a MS Word document)
Learning About Skin
To learn about the chemical properties of skin, you can put various substances on the outer surface and observe what happens. Some substances just stay on the surface, while other substances disappear (dissolve) into the skin.
- Make predictions/hypotheses on your observation journal page about what each of the substances will do once they contact skin.
- Turn your arm so that your palm is facing up. On your forearm, put a drop of water. Next to it, put a drop of lotion on your skin. Next to that place a drop of mineral oil. Finally, place a drop of rubbing alcohol on your skin. You should have 4 different substances on your skin. Spread out each drop on your skin to increase the surface contact of the various liquids, but do not rub them in. As you do so, be sure NOT to mix the substances together.
- Watch all four drops for 10 minutes without disturbing them. At the end of ten minutes, record your observations, including how the substances made your skin feel (oily or not, change in temperature?) and any changes to the substances.
- Which substances were absorbed by your skin? Which substances stayed oily? Record your observations.
- Answer follow-up questions on the Q/A response sheet using what you’ve learned from this experiment and also reflections from the “How We Find Out” section of this unit.
Activity Two: Bodily Defenses
- Why must our body have defense mechanisms? What are the defense mechanisms of the body and how do they work?
Skin
- Draw a cross-sectional picture of your skin and label the key parts. How is your skin a barrier.
- The Immune System: The “defenders” of the immune system are _______________________. They are rushed to the site of a wound or injury through the ________________. The _______________________ become concentrated in the injured area to stop _______________ from entering and damaging surrounding tissues.
- Describe what a vaccine is and what it is meant to do.
- Make a drawing of a white blood cell binding an antigen, then releasing an antibody, and then draw the interaction between the antigen that triggered its production. Make a drawing that shows the difference from the antibody’s reaction with OTHER antigens.
- Compare and contrast, using a Venn diagram, to show the differences in natural immunity and acquired immunity and what they have in common.
NOTE: Recall that there are really 2 types of lymphocytes, B-cells and T-cells. The B-type makes circulating antibodies. The B-type is made in lymph nodes and bone marrow. The T-type lymphocyte kills foreign cells on contact or helps by releasing chemicals that assist in killing invaders. T-cells recognize the surface proteins on other cells and when they come in contact with an intruder, the invading cells are killed. These lymphocytes are made in a gland at the base of the neck, called the thymus. Production of T-cells can be reactivated at any time, if a foreign antigen is presented. T-cells also play a role in the rejection of transplanted tissue and in fighting cancer.
- Compare and contrast, using a Venn diagram, to show the differences in natural immunity and acquired immunity and what they have in common.
- Why would the body not be adequately protected if it only had the B or T-cell immune system? Why does it need BOTH types of immune responses?
NOTE: In addition to the body’s natural defenses, vaccines may be administered to boost the body’s immunity and prevent disease. For many diseases, the vaccine contains the infection, but it is weakened. The goal in vaccine manufacturing is to make the infectious organism weak enough so that it won’t cause the disease but strong enough so that it will activate the body’s immune system.
Once the immune system is activated by the disease agent, antibodies are created to fight the disease. The antibodies are “programmed” specifically to fight that particular infectious agent. The original antibodies that are generated in response to a vaccination eventually go away, but the immune system has a “memory”.
After a vaccination, if the disease agent that was vaccinated against enters the body, new antibodies are immediately created using the “programming” from the old vaccine. The new antibodies are specifically developed to destroy the specific disease agent that has entered the body.
- Why would the body not be adequately protected if it only had the B or T-cell immune system? Why does it need BOTH types of immune responses?
- Make a list of diseases for which there are vaccines. Make one list for humans and one for animals. Make another list of diseases for which there are NO vaccines, categorizing the list, once again, by human and animal diseases.
- Research some of the human vaccines you have listed. Indicate how often the vaccination has to be repeated and any other interesting information you find out about different vaccines. Be sure to write down the websites or books you use to find your information (your sources).
- State the two types of white blood cells and explain the functions of each.
- Draw a concept map of how your body’s defense mechanisms attack bacteria and viruses.
Special Hazards
Sunburn
As you may recall from the “Common Hazards” section of our unit, sunburn results when the amount of exposure to the sun or other UV light source exceeds the ability of the body’s protective pigment, melanin, to protect the skin. Fair-skinned people with light-colored hair are at greatest risk of sunburn because their bodies produce lower amounts of melanin. While dark skin has more natural protection from the sun, it, too, can burn. Considering this information, answer the following using your Q/A Response Sheet and other resources if you have access to them:
- Radiation from the UV light (sunlight) has to hit something in order for it to dissipate its energy. Melanin provides molecules that safely absorb radiation energy. How does this protect the tissues of your body and your skin?
- When you sit outside for too long, you get sunburned. What is happening underneath the surface of the skin to allow the sunburn to occur?
- When you go into a swimming pool, do you see the burn immediately or after a few hours? Why do you think this is so?
- What time of the day is most dangerous when it comes to sunburn?
- The most common form of skin cancer is the most dangerous, melanoma. The word “melanoma” means that melanin in the body has become cancerous. Why do you think that these cells are more prone to cancer?
- What is the best way to prevent sunburn that could develop into skin cancer?
- What SPF sunscreen would you need to stay in the sun for 200 minutes if you are normally okay in the sun for 5 or 6 minutes?
- What percentage of melanin do you think can be found in the skin of an American Indian? What is different about their pigmentation that causes their skin to have a distinctive coloring?
AIDS
As you’ve read in “Common Hazards,” AIDS stands for “Acquired Immune Deficiency Syndrome”: Acquired means you can catch it; Immune Deficiency means a weakness in the body’s system that fights diseases. Syndrome means a group of health problems that make up a disease.
AIDS is caused by a virus called HIV: Human Immunodeficiency Virus. When you get a blood test for HIV, the test is really for antibodies. If you have them in your blood, it means that you have HIV infection. People who have the HIV antibodies are called “HIV-Positive”.
Being HIV-positive, or having HIV disease, is not the same as having AIDS. Many people are HIV-positive but don’t get sick for many years. As HIV disease continues, it slowly wears down the immune system. Viruses, parasites, fungi and bacteria that usually don’t cause any problems can make you very sick if your immune system is damaged. These are called ” opportunistic infections”.
Answer the following using information from this unit, other web-based resources, or printed sources:
