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INFECTIOUS DISEASES AND THE IMMUNE SYSTEM
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| INFECTIOUS DISEASE AND
THE IMMUNE SYSTEM The human body is continuously exposed to pathogens, such as viruses and bacteria. When one of these pathogens enters the body and begins to multiply, it causes an INFECTIOUS DISEASE. This section examines the body's Nonspecific Defenses, which are the First Lines of Protection against invading pathogens. OBJECTIVES: Summarize Koch's postulates for identifying a disease-causing agent. Describe how the skin and mucous membranes protect the body against pathogens. Describe the steps of the inflammatory response. Identify the white blood cells involved in a nonspecific response, and describe their functions. Explain the functions of interferon and fever. 1. Immunity may be defined as the body's ability to destroy Pathogens or other Foreign Material and to prevent further cases of certain Infectious Diseases. This ability is of vital importance because the body is exposed to Pathogens from the moment of Birth. WHAT IS DISEASE? 1. ANY CHANGE, OTHER THAN AN INJURY, THAT INTERFERES WITH NORMAL FUNCTIONING OF THE BODY IS A DISEASE. 2. Different diseases can be recognized by their SYMPTOMS, or CHANGES THEY PRODUCE IN THE BODY. 3. Diseases can be caused by many different things - INFECTIOUS DISEASES are produced by PATHOGENS. 4. PATHOGENS are disease-causing microorganisms, such as Viruses, Bacteria, Rickettsiae (rih-KEHT-see-ee), Fungi, and Protozoans. 5. When the body is Successfully Invaded by a Pathogen, we say that an INFECTION has occurred. 6. The numbers of microorganisms in the world around us are so Large that Infection is a Daily Event. 7. Sickness is NOT a daily event because NOT ALL Infections produce Disease. 8. Infectious Disease results only when the Growth of a Pathogen begins to Injure the Cells and Tissues of an Infected Person. 9. The Relationship between a Pathogen and the Organism it Infects is Essentially that of a Parasite and its Host. 10. A Parasite is an organism that obtains Nutrition from the body of the Host in a way that HARMS the Host. 11. The Parasitic lifestyle of the Pathogen enables it to take advantage of the Host and to ultimately become Dependent upon the Host Organism for its Survival. SPREAD OF DISEASES 1. Many Pathogens are present in the Environment and require ONLY the Opportunity to Enter the Body to Produce Disease. 2. Some Infectious Disease-such as the Common Cold, Measles, Mumps, and Influenza (FLU)-are Spread from One Person to Another through Coughing and Sneezing (Airborne). 3. Other Infectious Disease spread through contaminated Water Supplies or Food that has been handled by People Infected with a Disease. 4. Other Infectious Diseases are spread by Infected Animals such as Ticks and Mosquitoes. 5. Sexual Contact is another way in which Diseases are spread. THE GERM THEORY OF INFECTIOUS DISEASE 1. For thousands of years people believed that Diseases were caused by evil spirits, magic, or miasmas (vapors rising from marshes or decaying plant or animal matter). 2. People actually Feared that those who became ill were Cursed or had brought Bad Luck with them. 3. A New Idea developed in the nineteenth century explained the origins of Infectious Diseases, Based on the work of French Chemist Louis Pasteur and the German Physician Robert Koch, it was Shown that Infectious Diseases were Caused By MICROORGANISMS. 4. THIS IDEA IS NOW KNOWN AS THE GERM THEORY OF INFECTIOUS DISEASES. 5. Koch's experiments and observation led him to develop a series of RULES for PROVING that a SPECIFIC TYPE of Microorganism CAUSES a SPECIFIC DISEASE. 6. Or A STEP BY STEP METHOD FOR IDENTIFYING THE PARTICULAR PATHOGEN RESPONSIBLE FOR A DISEASE. 7. THESE STEPS ARE CALLED KOCH'S POSTULATES: A. The Suspected Pathogen must occur in the body of an animal with the disease and NOT in the Body of a Healthy Animal. B. The Suspected Pathogen Should be Isolated and Grown in a Laboratory Culture. (Pure Culture) C. When the microorganisms grown in pure culture are Injected into a Healthy Animal, The Animal should develop the disease. D. The Pathogen from the Second Animal Should be isolated and grown in the Laboratory. It Should be the same as the Pathogen isolated from the first animal. (Throat Culture - STREP THROAT- caused by a Bacterium Streptococcus pyogenes) 8. Koch's Postulates enabled scientist to determine whether a particular Microorganism causes a Disease. These Postulates are still in use today in the study of Infectious Disease. SKIN AND MUCOUS MEMBRANES - "THE FIRST LINE OF DEFENSE" 1. THE MAIN FUNCTION OF THE IMMUNE SYSTEM IS TO FIGHT INFECTIOUS DISEASE. THE IMMUNE SYSTEM IS THE BODY'S DEFENSE SYSTEM AGAINST ATTACK. 2. PATHOGENS ARE A VIRUS OR ORGANISM THAT CAUSES AN INFECTIOUS DISEASE. 3. INFECTIOUS DISEASE IS ANY ILLNESS CAUSED BY ORGANISMS OR VIRUSES THAT ENTER AND REPRODUCE INSIDE THE HOST. 4. SOME COMMON INFECTIOUS DISEASES: COMMON COLD, INFLUENZA, CHOLERA, STREP THROAT, AND MALARIA. 5. Pathogens are part of your Environment. You probably contact hundreds of potential pathogens each day. 6. Although infectious diseases are caused by many different Pathogens, most infectious diseases are spread in one of FOUR WAYS: A. Through DIRECT CONTACT with an infected person (SEXUAL CONTACT). B. Through INDIRECT CONTACT with an infected person (COUGHING OR SNEEZING). C. Through contaminated food or water. D. Through the bite of and infected animal. 7. Infectious diseases that can be spread from one person to another are called CONTAGIOUS DISEASES. 8. THE IMMUNE SYSTEM IS OUR PRIMARY DEFENSE AGAINST DISEASE CAUSING MICROORGANISMS. 9. THE IMMUNE SYSTEM CONSISTS OF NONSPECIFIC AND SPECIFIC DEFENSES AGAINST INFECTIONS. 10. NONSPECIFIC DEFENSES ARE THE BODY'S FIRST LINE AGAINST DISEASE. THEY ARE NOT DIRECTED AGAINST A PARTICULAR PATHOGEN. 11. NONSPECIFIC DEFENSES GUARD AGAINST ALL INFECTIONS, REGARDLESS OF THEIR CAUSE. 12. SPECIFIC DEFENSES ARE ATTEMPTS BY THE BODY TO DEFEND ITSELF AGAINST PARTICULAR PATHOGENS. 13. Since Pathogens must enter the body in order to cause disease, the body's first line of defense is to keep pathogens out. 14. The Body's MOST IMPORTANT Nonspecific Defense is the SKIN. UNBROKEN Skin provides a continuous layer that protects almost the whole body. Very Few Pathogens can penetrate the layers of dead cells at the skin's surface. 15. Oil and sweat glands at the surface of the skin produce a salty an acidic environment that kills many bacteria and other microorganisms. 16. The importance of the Skin as a Barrier against Infections becomes obvious when a small portion of skin is broken or scraped off: Infection almost always follows. 17. Infections are a result of the penetration of the broken skin by microorganisms normally present on the unbroken skin. 18. Pathogens also enter the body through the Mouth and Nose, but the body has Nonspecific Defenses that protect those openings. 19. MUCOUS MEMBRANES are Epithelial Tissues that protect the interior surfaces of the body that may be exposed to pathogens. 20. Mucous membranes serve as a barrier and secret MUCUS, a sticky fluid that traps pathogens. 21. MUCUS, CILIA, and HAIRS in the Nose and Throat trap Viruses and Bacteria. Cilia in the Trachea trap Bacteria, Pathogens that make it to the Stomach are destroyed by Stomach Acid and Digestive Enzymes. 22. Many Secretions of the Body, including MUCUS, SALIVA, SWEAT, and TEARS, CONTAIN LYSOZYME, AN ENZYME THAT BREAKS DOWN THE CELL WALL OF MANY BACTERIA. THE INFLAMMATORY RESPONSE "THE SECOND LINE OF DEFENSE" 1. Despite the initial Defenses of the Skin and Mucous Membranes, Pathogens sometimes Enter the Body. 2. When Pathogens enter the Body, the Immune System has a Second Line of Defense. The Body's Second Line of Defense acts when TISSUES are Injured. 3. The injured cells release a Chemical called HISTAMINE, which starts a series of changes called the Inflammatory Response. 4. THIS SECOND LINE OF DEFENSE IS CALLED THE INFLAMMATORY RESPONSE. 5. THE INFLAMMATORY RESPONSE IS A NONSPECIFIC DEFENSE REACTION OF THE BODY TO TISSUE DAMAGE. 6. Histamine increases blood flow to the injured area and increases the permeability of the surrounding capillaries, as a result, Fluid and White Blood Cells (WBC) to leak from blood vessels into nearby tissue. 7. Pathogens are attacked by PHAGOCYTES, WHICH ARE WBCs THAT ENGULF AND DESTROY PATHOGENS BY PHAGOCYTOSIS. 8. The most common type of Phagocyte is the, 50 to 70 percent of the White Blood Cells in the body, is the NEUTROPHIL. 9. Neutrophils circulate freely through blood vessels, and they can squeeze between cells in the walls of a capillary to reach the site of infection. They then engulf and destroy any pathogens they encounter. 10. Another type of Phagocyte is the MACROPHAGE, they consume and destroy any pathogens they encounter, they also rid the body of worn out cells and cellular debris. 11. Some Macrophages are stationed in the tissues of the body, awaiting pathogens, while others move through the tissues and seek out pathogens. 12. NATURAL KILLER CELLS are large white blood cells that, unlike phagocytes, attack cells that have been infected by pathogens, Not the Pathogen Themselves. 13. Natural killer Cells are particularly effective in killing Cancer Cells and Cells Infected with Viruses. 14. A Natural Killer Cell punctures the cell membrane of its target cell, allowing water to rush into the cell, causing the cell to burst. (CYTOLYSIS) 15. If the infection remains small and in one place, a Reddish Swollen Area develops just beneath the skin. The area is said to be INFLAMED ("on fire"). The familiar symptoms of inflammation caused by the release of Histamine. 16. A serious Infection may allow pathogen to spread throughout the body. The Immune System now responds in two ways: A. It produces more WBCs. B. It releases chemicals that stimulate the actions of these White Cells by Increasing Temperature. Causes a FEVER. Elevated body temperature above normal 37 degrees C (99 F) due to Fever offers powerful protection. 17. Physicians know that a Fever and an Increase in WBCs are two indications that the body is fighting infection. 18. Fever is not a Disease; it is a Sign that the body is responding to an Infection. 19. Fever also serves another important function: Many diseases causing microorganisms can survive within only a narrow temperature range. A Fever can often Slow down or Stop the growth of some microorganisms. 20. In general, body temperatures greater than 39 degrees C (103 F) are considered Dangerous, and those greater than 41 degrees C (105 F) are often fatal. INTERFERON - DEFENSE AGAINST VIRUSES 1. Two Components of the Immune System fight only Viruses: INTERFERON AND NATURAL KILLER CELLS. 2. Because these components attack many types of viruses, the are considered Nonspecific Defenses. 3. Interferon is a Protein that interferes with the Replication of Viruses. Interferon is released by cells that have been invaded by Viruses. 4. Although interferon cannot Save an invaded cell, it works as a warning signal for healthy cells, in which it interferes with viral replication. These effects on a virus slow down the progress of infection and often give the Specific Defenses of the Immune System time to respond. 5. Natural Killer Cells, which also defend the body against Viruses, are contained in blood and lymph. 6. These cells attack Body Cells that have been infected by Viruses. Because viruses can only replicate in a Host Cell, Killing the Host Cell also destroys the Virus. 7. Interferon and Natural Killer Cells also help to fight against Cancer Cells. SPECIFIC DEFENSES: THE IMMUNE SYSTEM (IMMUNITY) "THIRD LINE OF DEFENSE" Although the nonspecific defenses usually keep pathogens from entering and becoming established in the body, pathogens occasionally break through these defenses and begin to multiply. In response, the body's specific defenses are called into action. Unlike the nonspecific defenses, the specific defenses act against on particular pathogen. OBJECTIVES: Identify and describe the components of the immune system. Explain the function of the three kinds of T cells. Describe the actions of B cells in an immune response. Explain how a vaccine works. Contrast allergy with autoimmune disease. Define antigen and antibody. List several specific defenses of the body. 1. IF A PATHOGEN IS ABLE TO GET PASS THE BODY'S NONSPECIFIC DEFENSES, THE IMMUNE SYSTEM REACTS WITH A SERIES OF SPECIFIC DEFENSES THAT ATTACK THE DISEASE CAUSING AGENT. 2. RESPONSES OF THE IMMUNE SYSTEM TO SPECIFIC PATHOGENS ARE CALLED SPECIFIC DEFENSES. 3. THE SPECIFIC DEFENSES OF THE BODY ARE COLLECTIVELY KNOWN AS THE IMMUNE RESPONSE. 4. A SUBSTANCE THAT TRIGGERS THE SPECIFIC DEFENSES OF THE IMMUNE SYSTEM IS KNOWN AS AN ANTIGEN. 5. AN ANTIGEN IS A SUBSTANCE THAT A MACROPHAGE (WBC) IDENTIFIES AS NOT BELONGING TO THE BODY. THE IMMUNE SYSTEM 1. The body's Specific Defenses are part of the Immune System. The Immune System has the job of fighting off invading pathogens and preventing the growth and spread of cancers. 2. The Immune System Consists of Several Organs, as well as White Blood Cells in the Blood and Lymph. 3. The Organs of the Immune System are scattered throughout the body; they include the BONE MARROW, THYMUS, LYMPH NODES, TONSILS, ADENOIDS, AND SPLEEN. 4. Each organ of the immune system plays a different role in defending the body against pathogens. 5. Bone Marrow manufactures the billions of WBC needed by the body every day. Some newly produce WBC remain in the bone marrow to Mature and Specialize, while others travel to the Thymus to Mature. 6. Lymph Nodes Filter Pathogens from the Lymph and expose them to WBC. 7. The Spleen, a fist-sized organ located behind the stomach, Filters Pathogens from the Blood. It is stocked with WBC that respond to the trapped pathogens. 8. THE WHITE BLOOD CELLS OF THE IMMUNE SYSTEM ARE KNOWN AS LYMPHOCYTES. These WBC accumulate in the Lymph and Lymph Nodes, but Lymphocytes are also found in the Spleen and Blood. 9. LYMPHOCYTES ARE WBCs THAT ACTIVATE THE IMMUNE RESPONSE. There are TWO Main Types of Lymphocytes: B Cells and T Cells. 10. B-LYMPHOCYTES (B Cells), WHICH ARE PRODUCED AND MATURED IN THE BONE MARROW ARE RESPONSIBLE FOR PRODUCING ANTIBODIES. 11. ANTIBODIES ARE SPECIAL PROTEINS THAT CAN BIND TO THE ANTIGEN ON THE SURFACE OF A PATHOGEN AND HELP DESTROY IT. RECOGNIZING PATHOGENS 1. Lymphocytes are the body's Specific Defense. 2. When the body is invaded by a pathogen, Lymphocytes launch an attack known as an IMMUNE RESPONSE to Eliminate the Pathogen. 3. In order to Respond to Pathogens, Lymphocytes MUST BE ABLE TO RECOGNIZE IT AS A FOREIGN INVADER AND DISTINGUISH IT FROM CELL OF THE BODY. 4. Any Substance that the Immune System recognizes as a Potential Pathogen and provokes an Immune Response is known as an ANTIGEN. 5. A wide variety of substances can be Antigens; Pathogens or Parts of Pathogens, Bacterial Toxins, Insect Venom, and Pollen. 6. Lymphocytes have Receptor Proteins on their Cell Membranes that Recognize and bind to Antigens that MATCH Their Particular Three-Dimensional Shape. 7. ALL of the Receptors on an individual Lymphocyte are the SAME Shape and thus Bind to the Same Antigen. 8. The body can defend itself against a large number of different pathogens because the Immune system makes millions of different kinds of Lymphocytes each carrying uniquely shaped receptors. 9. The Specificity of the Immune System is DUE TO the Specificity of the Antigen Receptors on the Lymphocytes. IMMUNE RESPONSE 1. An Immune Response is a TWO-PRONG Assault on a Pathogen: THE CELL MEDIATED IMMUNE RESPONSE AND THE HUMORAL IMMUNE RESPONSE. 2. Both parts of the Immune Response are Controlled by a Type of T CELL called a HELPER T CELL. 3. The FIRST STEP in an Immune Response occurs when a Macrophage engulfs and destroys a Pathogen. 4. The Macrophage then Displays Fragments of the Pathogen's Antigens on the surface of its own Cell Membrane. 5. When a Helper T Cell with a receptor matching this Antigen encounters the Macrophage, the Macrophage Releases a Cytokine called INTERLEUKIN-1, which in turn triggers the Helper T Cell to release a Second Cytokine, called INTERLEUKIN-2. CELL MEDIATED IMMUNE RESPONSE 1. Interleukin-2 Stimulates the Helper T Cells and Two other Types of T Cells - Cytotoxic T Cells and Suppressor T Cells to Rapidly divide. 2. IN CELL MEDIATED IMMUNITY, SPECIAL DEFENSE CELLS ATTACK CELLS THAT ARE DANGEROUS TO THE BODY. 3. CELL MEDIATED IMMUNITY ATTACKS BODY CELLS THAT ARE INFECTED WITH PATHOGENS, THAT ARE CANCEROUS, OR ATTACKS BODY CELLS FROM ANOTHER PERSON (TRANSPLANTS). 4. THE SPECIAL DEFENSE CELLS USED IN CELL MEDIATED IMMUNITY ARE T LYMPHOCYTES, (Cytotoxic T CELLS). 5. Cytotoxic T CELL ARE WBCs THAT ATTACK AND DESTROY FOREIGN AND DANGEROUS CELLS (Cancer). Cytotoxic T-Cells attach to foreign, antigen-bearing cells, such as bacteria cells, and interact directly- that is, by cell-to-cell contact. This type of response is called Cell-Mediated Immunity. 6. Suppressor T Cells help to shut down the Immune Response after the Pathogen has been cleared from the body. 7. T Cells are made in the Bone Marrow but MATURE in the THYMUS GLAND, T CELLS DO NOT PRODUCE ANTIBODIES. HUMORAL IMMUNE RESPONSE, (BODIES FLUIDS) - ANTIBODIES 1. Interleukin-2 and Antigen Presentation by a Macrophage or t Cell STIMULATES B CELLS to divide and Differentiate into PLASMA CELLS. 2. Plasma Cells are Highly Specialized Cells that produce Defensive Proteins and Secrete them into the Blood. 3. These Defensive Proteins are IDENTICAL to the Plasma Cell's Antigen Receptors and are known as ANTIBODIES. 4. THE ANTIBODY MOLECULE IS THE BASIC FUNCTIONAL UNIT OF THE IMMUNE RESPONSE. 5. An Antibody Molecule is shaped like the Letter Y and has TWO Identical ANTIGEN BINDING SITES that precisely fit the shape of a Particular Antigen. Lock and Key. 6. These sites allow each Antibody to bind to TWO Antigens. 7. Because an Antibody fits precisely with an Antigen, an Antibody that binds to one Antigen CANNOT bind to another Antigen. 8. Antibodies make Antigens CLUMP TOGETHER (AGGLUTINATION); the clumped Antigens are not active. Macrophages ENGULF and DESTROY the Clumped Antigens. 9. Because there are so many different Pathogens in the world, your body does NOT Automatically have antibodies against all of them. 10. When a Pathogen invades the body, a Macrophage brings the foreign Antigen to the B Cells (PLASMA CELLS). In this way, the B Cells "LEARN" about the Antigens on the Pathogens Surface and START to make appropriate Antibodies. The B Cells then circulate through the body, releasing Antibodies that bind to the new Antigen. 11. The production of Antibodies from the FIRST Exposure to an Antigen is known as the PRIMARY IMMUNE RESPONSE. IMMUNITY 1. THE GROWTH OF B CELLS AND T CELLS IN RESPONSE TO AN INFECTION HAS A SPECIAL CONSEQUENCE - IMMUNITY. 2. A person who is Resistant to a Specific Pathogen is said to have IMMUNITY TO IT. 2. ONCE THE BODY HAS BEEN EXPOSED TO A DISEASE, AND SURVIVED, A LARGE GROUP OF B CELLS AND T CELLS (MEMORY CELLS) REMAINS CAPABLE OF PRODUCING A SECONDARY IMMUNE RESPONSE SHOULD THE PATHOGEN REAPPEAR IN THE BODY. This is called NATURALLY ACQUIRED IMMUNITY. 3. THE BODY'S RESISTANCE TO PREVIOUSLY ENCOUNTERED PATHOGENS IS CALLED ACQUIRED IMMUNITY. 4. A SECONDARY IMMUNE RESPONSE IS MORE POWERFUL THAN THE PRIMARY RESPONSE, PRODUCING ANTIBODIES SO QUICKLY THAT THE DISEASE NEVER GETS A CHANCE TO DEVELOP. 5. THE RAPID RESPONSE OF THE IMMUNE SYSTEM TO A PATHOGEN IT HAS PREVIOUSLY ENCOUNTERED IS THE SECONDARY IMMUNE RESPONSE. 6. Memory B-Cells along with Memory T-Cells produce the Secondary Immune Response. 7. REMEMBER: THE PRIMARY IMMUNE RESPONSE OCCURS WHEN THE IMMUNE SYSTEM FIRST ENCOUNTERS A NEW PATHOGEN. 8. THERE ARE TWO TYPES OF IMMUNITY: A. ACTIVE IMMUNITY - The Immunity produced by a VACCINE is known an Active Immunity because the body has the ability to mount an active immune response against the pathogen. The injection of a WEAKENED or MILD form of a pathogen to produce immunity is known as VACCINATION. (LONG-LASTING) B. PASSIVE IMMUNITY - If Antibodies produced by other animals against a pathogen are injected into the bloodstream, they produce Passive Immunity against the pathogen as long as they remain in the Circulation, usually for several weeks. (SHORT-TERM) IMMUNE DISORDERS 1. THE IMPRESSIVE POWER OF THE IMMUNE SYSTEM TO DEFEND THE BODY AGAINST A WIDE RANGE OF POTENTIAL PATHOGENS COMES AT A PRICE: A. THE IMMUNE SYSTEM MAY OVERREACT TO AN ANTIGEN, PRODUCING DISCOMFORT OR EVEN DISEASE. B. THE CELLULAR NATURE OF THE IMMUNE RESPONSE IS A POTENTIAL WEAK POINT. A DISEASE ATTACKS THE LYMPHOCYTES. 2. The most COMMON Overreactions of the immune system are known as ALLERGIES. ALLERGIES 1. AN ALLERGY IS THE RESPONSE OF THE IMMUNE SYSTEM TO A NORMALLY HARMLESS SUBSTANCE AS IF IT WERE AN ANTIGEN. 2. Allergies result when Antigens bind to mast cells, which are a type of immune cell found throughout the body but especially in the linings of the nasal passage. 3. When allergy-causing antigen attaches to mast cells, the activated mast cells release Chemicals known as HISTAMINES. 4. Histamines Increase the flow of blood and fluids to the surrounding area, and produce sneezing, runny eyes and nose, and other irritations that makes a person with allergies miserable. 5. Antigen on plant pollen, dust, molds, and animal fur trigger allergies. 6. One of the most serious allergic reactions is ASTHMA, a condition in which smooth muscles contract around the passage to the lungs, making breathing difficult. 7. Asthma and Allergies can usually be treated with ANTIHISTAMINES (reverse the effects of Histamines) Drugs and other medicines. AUTOIMMUNE DISEASE 1. When the immune system is functioning Normally it distinguishes "SELF" from "NON-SELF". 2. But sometimes the immune system MISTAKES its own cells for pathogens, resulting in an AUTOIMMUNE DISEASE. 3. IN AN AUTOIMMUNE DISEASE, THE IMMUNE SYSTEM ATTACKS THE TISSUE OF THE BODY. 4. Several diseases are caused by IMMUNE disorders: A. RHEUMATIC FEVER RESULTING FROM STREP THROAT CAUSING CELL DEATH AND SCARRING TO THE HEART LINING AND THE HEART VALVES. B. RHEUMATOID ARTHRITIS A DESTRUCTIVE INFLAMMATION OF THE JOINTS. C. JUVENILE DIABETES REACTION AGAINST THE INSULIN PRODUCING CELLS OF THE PANCREAS. D. MULTIPLE SCLEROSIS A NERVE DISEASE THAT RESULTS FROM THE DESTRUCTION OF MYELIN SHEATH OF NERVE FIBERS. AIDS - ACQUIRED IMMUNODEFICIENCY SYNDROME The immune system normally provides very effective protection against infectious diseases. Its importance to our health is dramatically illustrated by the diseases in which the immune system malfunctions. The most deadly of these diseases is AIDS, or acquired immunodeficiency syndrome. Aids was first recognized as a disease in 1981, and since then it has killed more than 300,000 Americans. OBJECTIVES: Describe the course of HIV infection. Identify four ways HIV is transmitted. Describe how HIV's rate of evolution affects the development of vaccines and treatments. 1. AIDS STANDS FOR ACQUIRED IMMUNODEFICIENCY SYNDROME. AIDS IS THE MOST SERIOUS STAGE OF A CONDITION THAT DISRUPTS THE NORMAL FUNCTION OF THE IMMUNE SYSTEM. 2. AIDS IS NOT A Specific Disease, but a condition in which the immune system CANNOT protect the body against a variety of Pathogens. 3. AIDS IS CAUSED BY THE HUMAN IMMUNODEFICIENCY VIRUS OR HIV. HIV ATTACKS THE HUMAN IMMUNE SYSTEM AND DESTROYS THE BODY'S ABILITY TO FIGHT INFECTION. 4. Once HIV enters the body, it attaches to receptors on the surface of a type of T Cell known as HELPER T CELLS (T4 Cells). These cells are so named because they Help other Lymphocytes respond to the early stages of an infection. 5. As HIV destroys Helper T Cells, the body loses its ability to fight off disease. HIV Destroys the body's ability to defend itself. THE TRANSMISSION OF HIV 1. HIV CAN ONLY BE SPREAD FROM ONE PERSON TO ANOTHER ONLY THROUGH DIRECT CONTACT OF CERTAIN BODY FLUIDS, SUCH AS BLOOD, SEMEN, OR BREAST MILK. 2. HIV IS NOT SPREAD BY CASUAL CONTACT, SUCH AS HOLDING HANDS OR USING DISHES PREVIOUSLY USED BY A PERSON WITH HIV. 3. IT IS ALSO NOT TRANSMITTED BY INSECTS (Mosquitoes, Fleas, or Ticks). 4. MOST OFTEN, HIV IS TRANSMITTED THROUGH SEXUAL INTERCOURSE, SHARING NEEDLES, OR BY TRANSFUSION OF CONTAMINATED BLOOD. 5. HIV is now the fastest growing Epidemic in the world. 6. According to the United Nations AIDS Project, more than 22 Million people are infected with HIV. 7. EDUCATING YOURSELF ABOUT HIV CAN HELP REDUCE YOUR RISK OF GETTING THE DISEASE. A. CONDOMS REDUCE THE RISK OF TRANSMITTING HIV FROM ONE PERSON TO ANOTHER DURING SEXUAL INTERCOURSE. B. SHARING NEEDLES WITH OTHERS IS ONE OF THE MAIN WAYS THE VIRUS IS TRANSMITTED FROM PERSON TO PERSON. C. YOU NEVER RISK GETTING HIV WHILE DONATING BLOOD. BLOOD IS ROUTINELY TESTED FOR HIV, AND THIS HAS ALMOST ELIMINATED THE RISK OF GETTING HIV FROM BLOOD TRANSFUSIONS. 8. THERE IS NO KNOWN CURE FOR AN HIV INFECTION. 9. AT PRESENT, THE BEST WAY TO AVOID AN HIV INFECTION IS TO LEARN AS MUCH AS YOU CAN ABOUT THE WAYS HIV IS TRANSMITTED. 10. AVOID BEHAVIORS THAT PLACE YOU AT RISK OF CONTACTING THE VIRUS. STAGES OF HIV INFECTION 1. An HIV infection progresses on a fairly predictable course. Each stage of the infection is associated with certain symptoms, but the timing of the stages varies with different people. 2. When first infected by the virus, a person may have FLU LIKE Symptoms or no Symptoms. 3. Within a few weeks to several months, Antibodies to HIV begin to appear in the blood. 4. The presence of Antibodies in the blood is used to diagnose the disease and to screen donated blood. 5. A person is said to be HIV POSITIVE when HIV Antibodies are present in the blood. Even when a person is diagnosed as being HIV Positive, other Symptoms of the syndrome may not appear for months or even years. 6. In time, HIV attacks and destroys Helper T Cells, the helper cells that activate the immune system to fight infection. 7. At first, an HIV Positive person may experience a phase of mild symptoms including fever, weight loss, and swollen lymph nodes. 8. WHEN THE NUMBER OF HELPER T CELLS IN THE BLOOD BECOME SO LOW (Below 200/mL) THAT THE IMMUNE SYSTEM CANNOT FIGHT DISEASE, AN HIV INFECTION HAS DEVELOPED IN AIDS. 9. THE LENGTH OF TIME IT TAKES FOR AN HIV INFECTION TO BECOMES AIDS VARIES FROM PERSON TO PERSON, BUT IT MAY TAKE FROM A FEW TO 15 TO 20 YEARS. 10. People with AIDS may have a variety of diseases. Typically people with AIDS become sick when they are infected by pathogens that do not normally cause disease in people with healthy immune systems. These diseases are called OPPORTUNISTIC INFECTIONS. 11. AN HIV INFECTION IS GENERALLY CONSIDERED FATAL. HOWEVER, NOT EVERYONE WHO HAS BEEN DIAGNOSED AS HIV POSITIVE HAS DEVELOPED AIDS. 12. PEOPLE WITH AIDS DIE WHEN THEIR BODY'S WEAKENED IMMUNE SYSTEM CANNOT FIGHT OFF AN OPPORTUNISTIC INFECTION CAUSED BY A PATHOGEN. 13. Few individuals live more than two years after being diagnosed with AIDS, usually dying from Opportunistic Infections or Cancer. 14. Scientists trying to create Vaccines for HIV must contend with its Very Rapid Rate of Evolution. The Genes that Code for the Virus's surface proteins Mutate Frequently. 15. HIV's rapid evolution also complicates the task of developing Treatments (Drugs) for HIV Infection and AIDS. 16. The virus quickly becomes Resistant to drugs used against it. To avoid this problem, scientist have begun treating patients with Three Antiviral Drugs at once. |