The Immune System

1. The Immune System The Body’s Defense

2. The Body’s Lines of Defense • The body has three lines of defense against pathogens: • Barriers - skin, breathing passages, mouth, and stomach trap and kill most pathogens. • Inflammatory Response - fluid and some WBC’s leak from blood vessels into tissues to fight pathogens. • The WBC’s are called phagocytes- they engulf and destroy the pathogens. • Inflammatory responses include a red, swollen, warm area and sometimes fever. • Immune Response- these cells can distinguish between different kinds of pathogens and react to each kind with a specific defense.

3. Lymphocytes • WBC’s that target specific pathogens are called lymphocytes. • 2 major types: • T Cells- identify pathogens by recognizing their antigens. • Antigens are molecules that the immune system recognizes as either a part of your body or coming from outside your body. • B Cells- produce chemicals called antibodies. • Antibodies bind to antigens and destroy them. • Each kind of B Cell produces an antibody that can only bind to one kind of antigen.

4. Non-Infectious Diseases • Non-Infectious diseases are NOT caused by micro-organisms and are NOT spread from person to person. • Allergy- the immune system is overly sensitive to a foreign substance- something not normally found in the body. • Allergen- any substance that causes an allergy: dust, pollen, molds, some foods or medicines. • Histamine- chemical responsible for symptoms of allergies, like sneezing or watery eyes. • Asthma- when the respiratory passages narrow causing the person to wheeze and become short of breath.

5. Non-Infectious Diseases 2. Diabetes- when either your pancreas fails to produce enough insulin or your body’s cells cannot use it properly. As a result, there are high levels of glucose in the blood and glucose is excreted in the urine. The body cells do not contain enough glucose. • Insulin - produced by pancreas- chemical that enables your cells to take in glucose from the blood and use it for energy. • Type I Diabetes- most serious- person needs insulin injections. • Type II Diabetes - controlled by diet, weight control, and exercise.

6. Non-Infectious Diseases 3. Cancer - a disease in which cells multiply uncontrollably, over and over, destroying healthy tissue in the process. • Tumors develop when a cancerous cell divides over and over to form abnormal tissue masses. • Surgery, drugs, and radiation are used to treat cancer. • Carcinogens are substances or factors in the environment that can cause cancer. Avoid carcinogens such as tobacco or over-exposure to sunlight.

7. Infectious Diseases • Infectious diseases are disease that can pass from one organism to another. • Pathogens are organisms that cause disease. Diseases caused by pathogens are infectious. • The four major groups of human pathogens are: • Bacteria • Viruses • Fungi • Protists

8. Infectious Diseases • Bacteria- one-celled microorganisms • Examples include strep throat and tetanus. • Other bacterial pathogens produce a poison called a toxin that damages cells. • Viruses- smallest pathogens • Cannot reproduce unless inside living cells. • When viruses infect cells, the cells are damaged or destroyed, and the damaged cells release new viruses to infect other cells. • Examples include influenza (flu), colds, chicken pox, and AIDS.

9. Infectious Diseases • Fungi- example- athlete’s foot • Protist- example- malaria • Sources of pathogens include: • Another person - physical contact like shaking hands, or indirect contact like sneezing or coughing. • Contaminated object - eating food, drinking water, or using silverware that’s infected. • Animal Bite • Environment - tetanus and botulism live naturally in the environment.

10. Preventing Infectious Disease • Immunity- the body’s ability to destroy pathogens before they can cause disease • Two types of immunity: • Active- antibodies come from the person • Passive- antibodies come from outside the person

11. Preventing Infectious Disease • Active Immunity -occurs when a person’s own immune system produces antibodies in response to the presence of a pathogen. • T Cells and B Cells help destroy pathogens and keep a “memory” of the pathogen’s antigen. • Lasts for many years and sometimes for life. Ex: chicken pox. • Vaccination - (immunization)- harmless antigens are deliberately introduced to a person’s body to produce active immunity. • Vaccine - the substance used in vaccinations. Consists of pathogens that have been weakened or killed.

12. Preventing Infectious Disease • Passive Immunity - when the antibodies that fight the pathogen come from another source rather than the person’s own body • Lasts no more than a few months. • Babies acquire passive immunity to some diseases before birth from their mother. • You develop immunity from some diseases because you have had them before or you have been vaccinated. You will still become sick from them from time to time. • Antibiotics - chemicals that kill or slow down the growth of bacteria. • No medications cure viral illnesses!!