Section 1 Nonspecific Defenses Chapter 47 Objectives • SummarizeKoch’s postulates for identifying a disease-causing agent. • Describehow the skin and mucous membranes protect the body against pathogens. • Describethe steps of the inflammatory response. • Analyzethe roles of white blood cells in fighting pathogens. • Explainthe functions of fever and proteins in fighting pathogens.

Section 1 Nonspecific Defenses Chapter 47 Identifying Pathogens • A pathogen is any agent that causes disease and can be spread to humans through the air, food, water, or direct contact with an infected animal or person. • A disease that is caused by a pathogenic bacteria, virus, fungi, or protist is called an infectious disease. • Koch’s postulates are “rules” for identifying the particular pathogen that causes a specific disease.

Section 1 Nonspecific Defenses Chapter 47 Pathogen Click below to watch the Visual Concept. Visual Concept

Section 1 Nonspecific Defenses Chapter 47 Koch’s Postulates

Section 1 Nonspecific Defenses Chapter 47 Koch’s Postulates Click below to watch the Visual Concept. Visual Concept

Section 1 Nonspecific Defenses Chapter 47 First Line of Defense: Barriers • Nonspecific defenses, such as the skin and mucous membranes, are barriers to potential pathogens. • In addition to being a physical barrier to pathogens, skin also produces sweat, oils, and waxes, which are toxic to many bacteria. • A mucous membrane is a layer of epithelial tissue that covers internal surfaces of the body and secretes mucus, a sticky fluid that traps pathogens.

Section 1 Nonspecific Defenses Chapter 47 Second Line of Defense: Nonspecific Immunity • If a pathogen gets past the skin and the mucous membranes, the body triggers the second line of defense, which is nonspecific immunity. • Nonspecific immunity works in the same way against any pathogen. • Nonspecific immunity includes the inflammatory response, the temperature response, and 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 Inflammatory Response

Section 1 Nonspecific Defenses Chapter 47 Inflammatory Response Click below to watch the Visual Concept. Visual Concept

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 fevesr can be dangerous.

Section 1 Nonspecific Defenses Chapter 47 Fever as Nonspecific Defense Click below to watch the Visual Concept. Visual Concept

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 • Identifyand describe the parts of the immune system. • Explainhow the immune system recognizes pathogens. • Comparethe actions of T cells and B cells in the immune response. • Relatevaccination to immunity. • Distinguishbetween allergy, asthma, and autoimmune disease.

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 • Bone marrow, the thymus, lymph nodes, the spleen, adenoids, and tonsils are all part of the immune system. • Each part of the immune system plays a special role in defending the body against pathogens. • The specialized cells of the immune system are called lymphocytes. Lymphocytes are white blood cells that exists in two primary forms: T and B cells.

Section 2 Specific Defense: The Immune System Chapter 47 The Immune System, continued • 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.

Section 2 Specific Defense: The Immune System Chapter 47 How a Cytotoxic T Cell Recognizes an Infected Cell

Section 2 Specific Defense: The Immune System Chapter 47 Recognition of Pathogens Click below to watch the Visual Concept. Visual Concept

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 Cell-Mediated Immune Response Click below to watch the Visual Concept. Visual Concept

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System 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 Chapter 47 Primary and Secondary Immune Response Click below to watch the Visual Concept. Visual Concept

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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 Vaccine Click below to watch the Visual Concept. Visual Concept

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 2 Specific Defense: The Immune System Chapter 47 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.

Section 3 HIV and AIDS Chapter 47 Objectives • Describethe relationship between HIV and AIDS. • Distinguishbetween the three phases of HIV infection. • Identifythe two main ways that HIV is transmitted. • Determinehow the evolution of HIV affects the development of vaccines and treatment.

Section 3 HIV and AIDS Chapter 47 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.

Section 3 HIV and AIDS Chapter 47 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.

Section 3 HIV and AIDS Chapter 47 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.

Section 3 HIV and AIDS Chapter 47 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.

Section 3 HIV and AIDS Chapter 47 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 creat 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.

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