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The Body’s Defense Systems Chapter 47 Table of Contents Section 1 Nonspecific Defenses Section 2 Specific Defenses: The Immune System Section 3 HIV and AIDS
Section 1 Nonspecific Defenses Chapter 47 Objectives Identify a disease-causing agent. Describe bodies defenses against pathogens. Describe the inflammatory response.
White blood cells (shown here in gold) are the defensive cells in the body. White blood cells locate and destroy pathogens, such as the bacteria shown. What will happen to the bacteria after they are surrounded? The bacteria will be engulfed in a vacuole and digested by lysosomes.
Review Cell Structure and Function (Ch. 4): Describe the differences between eukaryotic cells and prokaryotic cells. Eukaryotic cells have nuclei, membranebound organelles, and divide through meiosis or mitosis. Prokaryotic cells do not have a nucleus or membrane-bound organelles, and divide by binary fission. Name some of the functions performed by cells. Reproduction Growth Metabolism
Review Pathogens (Ch. 23 and Ch. 24): List several differences between viruses and bacteria. Bacteria are alive, reproduce through binary fission, do not require a host for reproduction, and require nutrients. Viruses are not alive and require a host for reproduction. Explain how viruses replicate. Viruses insert their genetic material into a host cell, which replicates the virus.
Section 1 Nonspecific Defenses Chapter 47 Identifying Pathogens A pathogen is any agent that causes disease and can be spread to humans – What are common vectors of disease? air, food, water, or direct contact with an infected animal or person. A disease that is caused by a pathogen is called an infectious disease. – What are examples of pathogens? bacteria, virus, fungi, or protist Pathogens
Chapter 47 Koch’s Postulates Section 1 Nonspecific Defenses Koch's Postulates “Rules” for identifying a pathogen that causes a specific disease.
Section 1 Nonspecific Defenses Chapter 47 First Line of Defense: Barriers Nonspecific defenses – What types of physical barriers do we have that protect us from pathogens? the skin and mucous membranes – skin also produces sweat, oils, and waxes, which are toxic to many bacteria. – mucous membrane is a layer of epithelial tissue that covers internal surfaces of the body and secretes mucus, a sticky fluid that traps pathogens.
Chapter 47 Second Line of Defense: Nonspecific Immunity – Nonspecific immunity works in the same way against any pathogen. – Nonspecific immunity includes the inflammatory response the temperature response certain proteins.
Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity, continued Inflammatory Response – An inflammatory response is a series of events that suppress infection and speed recovery. – When cells are damaged they release chemical messengers, such as histamine. Histamine is a substance that increases blood flow to the injured area and increases the permeability of surrounding capillaries.
Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity, continued Inflammatory Response, continued – Fluids and white blood cells called phagocytes leak through capillary walls to fight any pathogens that may have entered the body. Phagocytes are cells that ingest and destroy foreign matter, such as microorganisms.
Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity, continued Inflammatory Response, continued – The most common phagocyte in the body is called a neutrophil. A neutrophil is a large leukocyte that contains a lobed nucleus and many cytoplasmic granules.
Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity, continued Inflammatory Response, continued – A macrophage is a white blood cell that engulfs pathogens and other materials. – Another type of white blood cell that attacks pathogen-infected cells is called a natural killer cell.
Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity, continued Temperature Response – When the body begins to fight pathogens, body temperature may increase. This rise in temperature is called a fever. – The body triggers a fever in order to slow bacterial growth or to promote white blood cell activity. – Though a moderate fever can be helpful, high fever can be dangerous. Fever as Nonspecific Response
Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity, continued Proteins – Proteins also provide nonspecific defenses. The complement system is a system of proteins that circulate in the bloodstream and become active when they encounter certain pathogens. Interferon is a protein released by cells infected with viruses that enables nearby cells to resist viral infection.
Section 2 Specific Defense: The Immune System Chapter 47 Objectives Identify and describe the parts of the immune system. Explain how the immune system recognizes pathogens. Compare the actions of T cells and B cells in the immune response.
Section 2 Specific Defense: The Immune System Chapter 47 The Immune System The immune system includes the cells and tissues that recognize and attack foreign substances in the body. The components of the immune system are found throughout the body.
Section 2 Specific Defense: The Immune System Chapter 47 The Immune System, continued What are the parts of the immune system? – Bone marrow, the thymus, lymph nodes, the spleen, adenoids, and tonsils.
Section 2 Specific Defense: The Immune System Chapter 47 The Immune System, continued The specialized cells of the immune system are called lymphocytes. – B cells are white blood cells that are made in the bone marrow and complete their development there or in the spleen. B cells make antibodies. – T cells are cells that are made in the bone marrow but complete their development only after traveling to the thymus. T cells also participate in many immune reactions.
Section 2 Specific Defense: The Immune System Chapter 47 Recognizing Pathogens Lymphocytes can provide specific defenses because they recognize pathogens by the antigens on their surface. An antigen is any substance that the immune system does not recognize as part of the body.
Section 2 Specific Defense: The Immune System Chapter 47 Recognizing Pathogens, continued Because the lymphocytes do not recognize the antigen, they start a specific attack known as an immune response. Lymphocytes recognize a pathogen with molecules on their surface called receptor proteins.
Section 2 Specific Defense: The Immune System Chapter 47 Recognizing Pathogens, continued An antigen has a complementary three- dimensional shape that allows the receptor protein to bind to it. This is how the lymphocyte recognizes the antigen. Only the specific receptor protein that is complementary to the antigen will be able to bind there.
Chapter 47 How a Cytotoxic T Cell Recognizes an Infected Cell Section 2 Specific Defense: The Immune System Recognition of Pathogens
Immune Response An immune response is a two-part assault on a pathogen. Both parts occur at the same time and require a specialized lymphocyte called a helper T cell. The two parts of the immune response are the cell-mediated immune response and the humoral immune response. T cells activate certain proteins that affect the behavior of other immune cells. These proteins are called cytokines.
Immune Response, continued Cell-Mediated Immune Response – In the cell-mediated immune response, cytokines activate more helper T cells and another type of T cell called a cytotoxic T cell. Cytotoxic T cells recognize and destroy cells that have been infected by a pathogen.
Section 2 Specific Defense: The Immune System Chapter 47 Immune Response, continued Cell-Mediated Immune Response, continued – Also produced during the cell-mediated immune response is a type of T cell called the suppressor T cell. – Suppressor T cells are thought to shut down the immune response after the pathogen has been cleared from the body. Cell Mediated Immune Response
Immune Response, continued Humoral Immune Response – The humoral immune response involves the action of B cells and occurs when antibodies are activated within body fluids. – The humoral immune response occurs at the same time as the cell-mediated immune response. – During the humoral response, cytokines stimulate B cells that have receptors that are complementary to the antigen to divide and change.
Immune Response, continued Humoral Immune Response, continued – Most B cells form plasma cells. A plasma cell is a white blood cell that produces antibodies. – Antibodies are defensive proteins that react to a specific antigen or inactivate or indirectly destroy toxins. – Antibodies use various methods to disable a pathogen or cause its destruction by nonspecific responses.
Immune Response, continued Primary and Secondary Immune Responses – The first time the body encounters an antigen, the immune response is called a primary immune response. – During this first encounter, the immune system fights off the disease. After the disease is overcome, the immune system creates memory cells. Memory cells are a B cell or T cell that will recognize and attack the antigen or invading cell during subsequent infections.
Immune Response, continued Primary and Secondary Immune Responses, continued – The second time the body encounters an antigen, a secondary immune response occurs. – During a secondary immune response, the immune response is faster and more powerful. – Most of the time, the secondary immune response protects the body from reinfection by a pathogen.
Chapter 47 The Immune Response Section 2 Specific Defense: The Immune System
Chapter 47 The Immune Response, continued Section 2 Specific Defense: The Immune System
Chapter 47 Primary and Secondary Immune Responses Section 2 Specific Defense: The Immune System Primary Secondary Immune Response
Section 2 Specific Defense: The Immune System Chapter 47 Immunity and Vaccination Immunity is the ability to resist an infectious disease. Immunity can come about in two ways: surviving an initial infection or through vaccination. – Vaccination is the introduction of antigens into the body to cause immunity.
Immunity and Vaccination, continued Vaccines – Vaccination usually involves an injection of a vaccine. – A vaccine is a solution that contains a dead or weakened pathogen or material from a pathogen that still contains antigens. – The immune system will produce a primary immune response to the antigens. Memory cells can then provide a quick secondary immune response if the antigen ever enters the body again. Vaccines
Problems of the Immune System Sometimes the immune system can react to harmless antigens. Three examples of this are allergies, asthma, and autoimmune diseases. Allergies – An allergy is a physical response to an antigen, which can be a common substance that produces little or no response in the general population.
Chapter 47 Allergy Section 2 Specific Defense: The Immune System
Problems of the Immune System Asthma – Allergies can trigger asthma. Asthma is a respiratory disorder that causes the bronchioles to narrow due to an overreaction to substances in the air. – During an asthma attack, the lining of the bronchioles and other respiratory tissues may also swell and become inflamed.
Problems of the Immune System AIDS (acquired immunodeficiency syndrome) is a disease caused by HIV (human immunodeficiency virus). – Infection by HIV causes the immune system to lose its ability to fight off pathogens and cancers. – HIV infection usually progresses to AIDS in three phases.
Objectives Describe the relationship between HIV and AIDS. Distinguish between the three phases of HIV infection. Identify the two main ways that HIV is transmitted. Determine how the evolution of HIV affects the development of vaccines and treatment.
The Course of HIV Infection AIDS (acquired immunodeficiency syndrome) is a disease caused by HIV (human immunodeficiency virus). – Infection by HIV causes the immune system to lose its ability to fight off pathogens and cancers. – HIV infection usually progresses to AIDS in three phases.
Chapter 47 AIDS (Acquired Immunodeficiency Syndrome) Section 3 HIV and AIDS
The Course of HIV Infection, continued Phase I – Phase I of HIV infection is called the asymptomatic stage, because there are few or no symptoms of the disease. – During this period of the disease the viruses increase rapidly due to replication. – Phase I can last up to 10 years or more.
The Course of HIV Infection, continued Phase II – The beginning or worsening of symptoms marks the start of the second phase of HIV infection. – B cells continue making antibodies, but T cells begin to decline steadily as the virus continues to replicate.
The Course of HIV Infection, continued Phase III – Phase III of HIV infection is the point where the number of helper T cells drops so low that they can no longer stimulate B cells and cytotoxic T cells to fight invaders. – AIDS is diagnosed when the helper T-cell count drops below a certain level.
The Course of HIV Infection, continued Phase III, continued – AIDS is also diagnosed if an opportunistic infection has developed. Opportunistic infections are illnesses caused by pathogens that produce disease in people with weakened immune systems. These organisms usually do not create problems in people with a healthy immune system. – Drug therapy can slow the progress of HIV infection to AIDS, but there is no cure for AIDS.
Chapter 47 Course of HIV Infection Section 3 HIV and AIDS Course of HIV
Transmission of HIV HIV is transmitted by the transfer of body fluids containing HIV or HIV-infected cells. This most commonly occurs by sexual contact with an infected person or by use of syringes and hypodermic needles that have been contaminated with blood containing HIV. HIV cannot be transmitted through casual contact.
Chapter 47 Known Routes of HIV Transmission Section 3 HIV and AIDS Spread of AIDS
Vaccines and Treatments Effective treatments and vaccines for HIV are difficult to create, because HIV has a rapid evolution rate. Treatment is also difficult because HIV quickly becomes resistant to antiviral drugs. Most HIV treatments are expensive and require a complicated multidrug therapy.