Chapter 37 Immune System The immune system attempts to protect the body from contracting an infection from pathogens

Infectious Diseases Pathogens are dispersed by people, animals, and objects.

Pathogens Cause Infectious Disease  infectious disease: caused by a pathogen passed from one organism to another  pathogens: cause infectious disease (Page 1078)  Bacteria  Viruses  Protozoans  Fungi  Parasites

Spread of Disease  Disease reservoir: source of the pathogen in the environment  Humans: main reservoir for pathogens that affect humans  Carrier : individual who is symptom-free, but is capable of passing on the pathogen  Colds, influenza, STDs, HIV, strep throat, chicken pox

Animal Reservoirs  Some animals are reservoirs of pathogens that can be passed to humans  Influenza: bird flu, swine flu  Rabies Other Reservoirs  Soil  Contaminated water or food  Tetanus

Vectors Transmission of Pathogens Indirect contact through air Indirect contact by objects Direct contact

Transmission of Pathogens Direct Contact: colds, mono, herpes Direct Contact: colds, mono, herpes Indirect Contact through air: sneezing, coughing; droplets carry pathogens Indirect Contact through air: sneezing, coughing; droplets carry pathogens Indirect contact by objects: dirty hands, utensils, surfaces in restaurants Indirect contact by objects: dirty hands, utensils, surfaces in restaurants Vectors: mosquitoes, ticks Vectors: mosquitoes, ticks

Symptoms of Disease  Virus: multiplies in cells; leaves the cells by exocytosis or by lysing the cell  damages tissues or kills cells  Bacteria: toxins might be produced  Tetanus  Botulism

Disease Patterns  As outbreaks of diseases spread, certain patterns are observed  Agencies monitor disease patterns to control the spread  Centers for Disease Control (CDC)  World Health Organization (WHO) Endemic diseases: continually found in small amounts in a population Epidemic: large outbreak in an area, affecting many people Pandemic: when the outbreak spreads throughout country, continent, or world

Treating and Fighting Diseases  Antibiotic: substance that can kill or inhibit the growth of bacteria  Penicillin  Erythromycin  Antibiotic resistance (graph page 1083)

The Immune System The immune system has two main components: nonspecific immunity and specific immunity.

Nonspecific Immunity Nonspecific Immunity 1 st and 2 nd line of defense 1 st and 2 nd line of defense will protect against any foreign substance will protect against any foreign substance Specific Immunity Specific Immunity 3 rd line of defense 3 rd line of defense Only used if 1 st and 2 nd lines of defense fail Only used if 1 st and 2 nd lines of defense fail Specific to each type of pathogen. Specific to each type of pathogen.

Skin Barrier – 1st line  Dead skin cells provide a barrier against invasion of microorganisms  Bacteria that live symbiotically on skin digest skin oils to produce acids that inhibit many pathogens

Chemical Barriers – 1st line  Saliva, tears, and nasal secretions contain the enzyme lysozyme  Lysozyme breaks down bacterial cell walls, which kills pathogens  Mucus acts as a protective barrier, blocking bacteria from sticking to inner epithelial cells  Cilia: hairs that continuously sweep upward, keeping bacteria away from the lungs  HCl in stomach; acid pH 2

1st Line of Defense Skin Barrier Skin cells and bacteria Chemical Barrier lysozymes kill pathogens. mucous membranes: line the digestive, respiratory tract, urethra, and vagina Mucous traps the pathogens Contain cilia brushes upward stomach – pH 2 Acid kills most pathogens

Nonspecific Responses to Invasion  2nd line of defense  2nd line of defense responds to pathogens that get past 1st line of defense barriers  Cellular defense  Interferon  Inflammatory response  Fever

Cells of the Immune System macrophage Phagocytes: macrophages, neutrophilsPhagocytes: macrophages, neutrophils Natural Killer cellsNatural Killer cells

Cells of the Immune System – 2 nd line Phagocytes: Phagocytes: Neutrophil: kill pathogens in the blood Neutrophil: kill pathogens in the blood Macrophage: wait in the body’s healthy tissues to destroy pathogens that enter Macrophage: wait in the body’s healthy tissues to destroy pathogens that enter Natural Killer Cells Natural Killer Cells attack body cells that are infected with pathogens; punctures cell membrane attack body cells that are infected with pathogens; punctures cell membrane cancer cells, viruses cancer cells, viruses

Cellular Defense  Phagocytes  phagocytosis: cells surround & engulf foreign pathogens lysozymes  lysosomes release digestive enzymes, lysozymes, which destroys the microorganism

Cellular Defenses Complement  Group of about 20 plasma proteins  Activated when they encounter an antibody attached to a pathogen lysis  Damage pathogen’s cell membrane - lysis

Interferon – 2 nd line  Virus - infected cells secrete a protein called interferon.  Interferon binds to neighboring cells and stimulates them to produce antiviral proteins which can prevent viral replication in these cells  Prevents the virus from spreading.

Fever – 2 nd line  Abnormally high body temperature  Hypothalamus “set point” is reset by pyrogens (secreted by white blood cells)  High temperatures inhibit the release of iron and zinc from liver and spleen needed by bacteria  Fever also increases the speed of tissue repair

Inflammatory Response – 2 nd line Damaged skin cells release Damaged skin cells release histamine; increases blood flow, WBC’s to fight infection attracts platelets & WBC’s to fight infection Results: red, sore, and swollen Results: red, sore, and swollen Excess WBC’s --> pus Excess WBC’s --> pus Platelets begin clotting process Platelets begin clotting process

Inflammatory Response – 2 nd line  Increased blood flow to the infected area makes blood vessels more permeable to allow white blood cells to escape into the infected area.

Functions of Inflammatory Response  Prevents spread of pathogens  Disposes of cell debris & pathogens  Sets the stage for repair

Antigens  “foreign protein” on a pathogen that causes an immune response  protein (antigen) can bind to an antibody or a T Cell

Recognizing Pathogens cells have proteins on their cell membrane that serve as ID tags for the body. cells have proteins on their cell membrane that serve as ID tags for the body. your cells’ ID tag is different from the ID tag (antigen) of a pathogen. your cells’ ID tag is different from the ID tag (antigen) of a pathogen. Your immune system recognizes the foreign ID tag (antigen) and attacks the pathogen. Your immune system recognizes the foreign ID tag (antigen) and attacks the pathogen.

Specific Immunity 3 rd Line of Defense  Antigen specific: recognizes and acts against particular foreign protein  Systemic: not restricted to the initial infection site  Memory: will recognize & mount a stronger attack next time it encounters the same pathogen

Specific Immunity – 3 rd line of defense  Lymphatic system  filters lymph & blood to destroy foreign microorganisms  Attacks a specific pathogen

Lymph Nodes Filter lymph and remove foreign materials Tonsils, Adenoids: lymph tissue between nasal & oral cavities. Spleen Stores blood, destroys damaged RBCs, filters pathogens, has many WBCs Bone Marrow Produces B Cells and T Cells Thymus Matures T Cells Lymphatic Organs

 Lymphatic tissue (lymph): fluid surrounds cells  Also found in mucous membranes of the intestinal, respiratory, urinary, and genital tracts  Lymphocytes: WBCs produced in red bone marrow.  B cells: produce antibodies, memory cells  T cells: mature in the Thymus gland  Helper T cells  Cytotoxic T cells

Antibodies  proteins produced by B lymphocytes that react with a specific foreign antigen  B lymphocytes, often called B cells, are located in all lymphatic tissues and can be thought of as antibody factories  Antibodies bind to pathogens & inactivate them so T cells can kill the pathogens

3rd Line of Defense Specific Immune Response (p. 1087) Antibody-Mediated Response Antibody-Mediated Response Cytotoxic T Cell Response Cytotoxic T Cell Response  B cells make antibodies to trap pathogens  T cells kill infected body cells

Specific Immune Response Step 1 (For Both Responses) Step 1 (For Both Responses) Macrophage engulfs pathogen Macrophage engulfs pathogen Macrophage displays the antigen of pathogen on its cell membrane Macrophage displays the antigen of pathogen on its cell membrane Specific Helper T Cell binds with antigen on macrophage Specific Helper T Cell binds with antigen on macrophage Activated Helper T Cell divides Activated Helper T Cell divides

Antibody - Mediated Response B Cell Response  activated helper T cell reproduces and displays processed antigens, then attaches to a B cell  newly formed B Cells manufacture antibodies that bind to the specific antigen, neutralizing it  activated B Cell divides  Some B Cells become Memory cells for the secondary response

Antibody - Mediated Response B Cell Response  Antibodies bind to antigens on pathogens, making them more susceptible to phagocytosis  initiate inflammatory response, which helps promote that nonspecific response

Cytotoxic T Cell Response  helper T cells bind to and activate cytotoxic (killer) T cells  activated cytotoxic T cells destroy pathogens & release chemicals called cytokines  cytokines stimulate the cells of the immune system to fight the infection

Passive Immunity  temporary protection occurs  contact with infectious disease or by immunization  exposed to disease antigens and memory cells are produced  antibodies made by other people or animals  transferred or injected into the body Active Immunity  Mother to baby through placenta or breast milk  2nd time exposed, memory cells immediately begin producing large quantities of antibodies  long term immunity

Primary vs Secondary Immune Response Primary: 1 st exposure Primary: 1 st exposure Occurs slowly because the body must make new antibodies Secondary: 2 nd or more exposure Secondary: 2 nd or more exposure Occurs quickly because the body’s memory cells “remember” the pathogen and can make antibodies much faster

Immunizations Vaccines contain a dead or weakened form of the pathogen. Vaccines stimulate a primary immune response The body makes memory cells –> long term protection plan

Noninfectious Disorders Noninfectious disorders include genetic disorders, degenerative diseases, metabolic diseases, cancer, and inflammatory diseases.

Inflammatory Diseases  The body produces an inflammatory response to a common substance.  Allergies Plant pollen, dust, dust mites, foods, animal dander, fungal spores Reactions: watery eyes, wheezing, sneezing (histamine release) Anaphylactic shock: massive release of histamines; bronchioles contract - bee stings, peanuts, latex penicillin

Autoimmune Diseases Immune system develops antibodies to its own proteins Immune system develops antibodies to its own proteins Multiple Sclerosis: myelin sheath Multiple Sclerosis: myelin sheath Rheumatoid Arthritis: joint tissue Rheumatoid Arthritis: joint tissue Lupus: cell nuclei Lupus: cell nuclei Rheumatic Fever: valves of the heart Rheumatic Fever: valves of the heart Ulcerative Colitis: lining of large intestine Ulcerative Colitis: lining of large intestine

Immune System Failure

HIV and AIDS H (Human) I (Immunodeficiency) V (Virus) attacks & kills T-cells specifically T-helper cell H (Human) I (Immunodeficiency) V (Virus) attacks & kills T-cells specifically T-helper cell Helper T cells become HIV factories, producing new viruses. As the virus multiplies, the number of helper T cells in an infected person decreases. Helper T cells become HIV factories, producing new viruses. As the virus multiplies, the number of helper T cells in an infected person decreases. HIV is spread through body fluids (blood and sexual intercourse) and syringes. HIV is spread through body fluids (blood and sexual intercourse) and syringes. A (Acquired) I D (Immunodeficiency) S (Syndrome) A (Acquired) I D (Immunodeficiency) S (Syndrome) A person does not die of HIV or AIDS but of an illness that the immune system cannot fight off. A person does not die of HIV or AIDS but of an illness that the immune system cannot fight off. Suppresses immune system Suppresses immune system Person cannot resist infection Person cannot resist infection

Immune System Failure  helper T cells become HIV factories, producing new viruses  # of helper T cells in an infected person decreases