the body’s defense systems chapter 47 table of contents section 1 nonspecific defenses section 2...

The Body’s Defense SystemsChapter 47

Table of Contents

Section 1 Nonspecific Defenses

Section 2 Specific Defenses: The Immune System

Section 3 HIV and AIDS

Section 1 Nonspecific DefensesChapter 47

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.

• Analyze the roles of white blood cells in fighting pathogens.

• Explain the functions of fever and proteins in fighting pathogens.


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.

Chapter 47

Click below to watch the Visual Concept.

Visual Concept

Pathogen


Chapter 47

Koch’s Postulates


Chapter 47


Visual Concept

Koch’s Postulates



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.


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.


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.



• 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.




– 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.




– 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.

Chapter 47

Inflammatory Response


Chapter 47


Visual Concept

Inflammatory Response




• 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.

Chapter 47


Visual Concept

Fever as Nonspecific Defense




• 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 SystemChapter 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.

• Relate vaccination to immunity.

• Distinguish between allergy, asthma, and autoimmune disease.


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.


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.


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.


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.


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.


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

Chapter 47


Visual Concept

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.



• 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.

Chapter 47


Visual Concept

Cell-Mediated Immune Response




• 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.



• 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.



• 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.



• 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


Chapter 47

The Immune Response, continued


Chapter 47

Primary and Secondary Immune Responses


Chapter 47


Visual Concept

Primary and Secondary Immune Response



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.

Chapter 47


Visual Concept

Vaccine



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.



• 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.



• 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 AIDSChapter 47

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.


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.



• 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.



• 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.



• 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.

Chapter 47

Course of HIV Infection



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


Chapter 47


Visual Concept

Course of an HIV Infection



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.

Chapter 47


Visual Concept

Spread of AIDS


the body’s defense systems chapter 47 table of contents section 1 nonspecific defenses section 2...

Documents