W ARM -U P #21 Complete Study Guide page 70.

T HE I MMUNE S YSTEM Infectious Disease

O BJECTIVES Identify the cause of disease. Explain how infectious diseases are transmitted. Describe how antibiotics fight infection.

D ISEASE A disease is any change, other than an injury that disrupts the normal functions of the body. Diseases are caused by: Agents, such as bacteria, viruses and fungi. Materials in the environment, such as cigarette smoke. Inheritance, such as hemophilia Infectious diseases are caused by agents. Disease-causing agents are called pathogens.

T HE G ERM T HEORY OF D ISEASE Louis Pasteur and Robert Koch—infectious diseases were caused by microorganisms of different types—called germs. Allen Steere, Lyme disease and deer ticks. Steere used Koch’s postulates to isolate the microorganism responsible for Lyme disease.

K OCH ’ S P OSTULATES The pathogen should always be found in the body of a sick organism and should not be found in a healthy one. The pathogen must be isolated and grown in the laboratory in pure culture. When the cultured pathogens are placed in a new host, they should cause the same disease that infected the original host. The injected pathogen should be isolated from the second host. It should be identical to the original pathogen. See Study Guide page 62

H OW DO PATHOGENS CAUSE DISEASE ? Some pathogens, including viruses and some bacteria, destroy cells as they grow. Other bacteria release toxins that harm an organism. Others, like parasitic worms, produce sickness when the block the flow of blood, remove nutrients from the digestive system, and disrupt other bodily functions.

H OW ARE DISEASES SPREAD ? Physical Contact Direct contact—touching, sexual contact Indirect Contact—cough, sneeze, hand to object to hand. Contaminated Food and Water Food poisoning—caused by bacteria in food Infected Animals—called vectors Mosquitos and malaria Ticks and Lyme disease Rabies

F IGHTING I NFECTIOUS D ISEASES Antibiotics—compounds that kill bacteria without harming the cells of the human or animal hosts. Antiviral medications—generally inhibit the ability of viruses to invade cells and to multiply once inside cells. Over-the-counter medication—treat the symptoms, not the infection

S UMMARY What causes disease? What causes infectious disease? What are Koch’s postulates? How are infectious diseases transmitted? How do antibiotics fight infection? How do antiviral drugs work?

T HE I MMUNE S YSTEM How our immune system works

O BJECTIVES Identify the body’s non-specific defenses against invading pathogens. Describe the function of the immune system.

I MMUNITY The function of the immune system is to fight infection through the production of cells that inactivate foreign substances or cells This process is called immunity. The immune system includes two general categories of defense mechanisms against infection: Non-specific Specific

Immunity Non Specific Defenses Skin Inflammatory Response FeverInterferons Specific Defenses Cell Mediated Immunity Humoral Immunity

F IRST LINE OF D EFENSE Your body’s most important non-specific defense is the skin. Very few pathogens can penetrate the layers of dead cells at the skin’s surface Secretions of the body, including mucus, saliva and tears contain lysozyme which breaks down the cell walls of many bacteria Oil and sweat glands in the skin produce an acidic environment that kills many bacteria.

S ECOND L INE OF D EFENSE If pathogens do enter your body, the inflammatory response is activated. Millions of WBCs are produced which fight the infection. Many of the WBCs are phagocytes which engulf and destroy bacteria. Blood vessels expand, speeding blood flow to the infection site. The immune system also releases chemicals that increase core body temperature—causing a fever. Virus infected cells produce a group of proteins that help other cells resist viral infection—these proteins are called interferons.

S PECIFIC D EFENSES If a pathogen is able to get past the non-specific defenses—the immune response is activated. A substance that triggers the immune response is known as an antigen. Two types of lymphocytes recognize specific antigens: B cells—humoral immunity T cells—cell-mediated immunity

T HE I MMUNE R ESPONSE Macrophages bring antigen proteins to T-cells after eating the pathogen T-cells (produced in bone marrow) [2 kinds] Helper T-cell interacts with B-cells Signals B-cell to become Plasma cells and produce antibodies in the blood (Up to 2000 antibody molecules per second!) Some B-cells don’t become Plasma cells and produce antibodies, but get prepared and wait….for future infection (Memory B-cells)

Check out the cartoon

I MMUNE R ESPONSE ( CONTINUED ) Killer T-cell – specific for a single antigen Insert enzymes directly into pathogen causing it to lyse and die

I MMUNE R ESPONSE S UMMARY Macrophage eats pathogen (puts antigen on surface) Proteins from antigen are expressed on macrophage surface T-cells recognize these antigen proteins as non-self and start signaling Some become Killer T-cells – secrete enzymes directly into infected cells and kill them Others become Helper T-cells which stimulates more Killer T-cell growth, and stimulates growth of B-cells and their production of antibodies (helper T- cells are like the conductor of an orchestra – telling everyone when and how to play) Study Guide 61 Video

Immunity Non Specific Defenses Skin Inflammatory Response FeverInterferons Specific Defenses Cell Mediated Immunity Humoral Immunity

A CQUIRED I MMUNITY Active Immunity Body makes its own antibodies Can develop as a result of natural exposure to an antigen (you only get the chicken pox once (usually)) Can be produced as a result of vaccination Passive Immunity Antibodies produced by other organisms and then inserted. Mother to child via breast milk

S UMMARY What are the body’s non-specific defenses against invading pathogens? Summarize the body’s specific defenses or immune response. What is the function of the macrophage? What is the function of the plasma B cells? The memory B cells? What is the function of the Helper T cells? The cytotoxic T cells?

S TUDY G UIDE 63 AND 65

H OMEWORK —DUE TUESDAY 4/5 Read Text Complete Study Guide 67-68