Immunity and Disease Chapter 39

What is an Infectious Disease? Any disease caused by pathogens Can be caused by bacteria, viruses, fungi, protists or other parasites that cause disease

Determining what causes disease Some are inherited hemophilia Some are due to aging arthritis Some are due to environmental factors lung cancer About half of all diseases are infectious

Robert Koch German Physician 1876 discovered rod- shaped bacteria in blood of dying cattle He injected blood into healthy animals and they died Discovered the Anthrax bacteria

Koch’s Postulates Steps used to relate certain pathogens to certain diseases Pathogens must be found in every case of the disease Pathogens must be grown in an isolated culture Isolated pathogens should cause disease in a healthy host Must be isolated from new host and be shown to be the original pathogen

Exceptions to Koch’s Postulates Some organisms cannot be grown in a culture Living tissue must be used to grow a virus

Reservoirs for Pathogens Carriers- people who harbor pathogens with out symptoms and spread the disease Incubation period- symptom free period while pathogens are multiplying Animals can be reservoirs for disease Soil and water can hold pathogens

Transmission of Disease Direct contact Common cold, flu, STD’s, ebola By an object Food poisoning Air borne Haunta Virus Vector- intermediate organism that transmits disease Arthropods and insects

What causes the symptoms? If it overcomes the immune system, then cells, tissues and organ damage can result Toxins disrupt metabolism of the cell Temperatures rise in an effort to kill the disease causing agent

Patterns of Disease Periodic outbreaks- occur occasionally - typhoid fever Endemic disease- ones that are constantly present in the human population- cold Epidemics- many people break out with the same disease at about the same time- polio, flu Pandemic-widespread over many continents or even worldwide-small pox, TB

Defense Against Infectious Diseases Section 39-2

Innate immunity The body’s earliest line of defense against any and all pathogens Includes skin and body secretions, inflammation of body tissues, interferons and phagocytosis of pathogens. Not pathogen specific

Skin and body secretions Your skin is a protective barrier Mucus Thick and traps pathogens Keeps areas of the body from drying out Swallowed and digestive juices destroy bacteria Sweat, tears and saliva Contain enzymes capable of breaking down cell walls of some bacteria

Skin Response

Inflammation of body tissues Characterized by redness, swelling, pain and heat Wbc’s release histamine to dilate blood vessels Vessels release fluid into infected area to destroy toxic agents

Phagocytosis of pathogens Phagocytes are WBCs that engulf pathogens and destroy them Macrophages- 1 st line of defense Neutrophils- 2 nd line of defense Monocytes- smaller and travel in bloodstream and then swell into macrophages Pus forms and is later removed by macrophages

Neutrophil engulfing bacteria

Phagocytosis

Interferons Protective proteins that protect your body from viruses Host specific- viral infections of human cells are inhibited only by human interferons Produced by cells infected by the virus Spread to other cells to make them resistant to the virus Prevent virus from multiplying

Acquired Immunity -Defending against a specific pathogen by gradually building up a resistance to it. White blood cells learn to recognize specific foreign substances Antigen- foreign substances that stimulate an immune response Antibody- proteins that correspond to each antigen Job of the Lymphatic system

What is an antibody?

This is how anti-venom is made Horses are injected with venom and produce antibodies

Antibody(humoral) Immunity Chemical warfare within your body that involves several types of cells Macrophages engulf pathogen T Cells Helper T cells activate B cells Suppressor T cells- suppress activation of the immune system B Cells Become plasma cells and produce antibodies Some become memory B cells that stay to defend

Antigen Production

Humoral Immunity

Memory cells

Cellular Immunity Macrophages engulf pathogens  Helper T cells Transform into cytotoxic T cells (antigen specific) Release cytokines to elicit an immune response Cytotoxic T cells kill the pathogen immediately and do not produce antibodies Clone themselves to reproduce release enzymes causing pathogens to lyse and die

Made up of two cellular systems humoral or circulating antiBody system - B cells cell mediaTed immunity - T cells

Passive Immunity Can be passed from mother to child (natural) Inject antibodies from another organism that has already been exposed(artificial) Anti-venom for snake bites

Active Immunity Occurs naturally when a person is exposed Can be induced artificially by a vaccine Edward Jenner used the cowpox virus to create a smallpox vaccine

The Lymphatic System Defends against disease Maintains homeostasis Keeps body fluids at a constant level Major organs Tonsils Spleen Appendix Lymph nodes Thymus gland

The lymphatic System

Glands of the Lymphatic System Lymph- tissue fluid in the lymph vessels Lymph node- small mass of tissue that contains lymphocytes and filters pathogens from the lymph Lymphocyte- a wbc that defends the body against foreign substances

Tonsils Tonsils are glandular tissue located on both sides of the throat. Trap bacteria and viruses entering through the throat and produce antibodies to help fight infections Can become swollen

Lymphatic Sys. Cont. Spleen Stores certain types of lymphocytes Filters out and destroys bacteria and worn out red blood cells Acts as a blood reservoir Does not filter lymph Thymus gland Stores immature lymphocytes until mature

Thoracic Duct the main trunk of the system of lymphatic vessels that lies along the front of the spinal column and opens into the left subclavian vein.

Appendix The appendix represents a blind out pocketing off of the large intestine. contain enormous deposits of lymphoid tissue infiltrated with lymphocytes. Possibly a vestigial remnant of the cellulose digesting cecum. Protects and harbors good bacteria

Peyers patches Gut-associated Lymphoid Tissue (GALT) clusters of lymphoid nodules loose connective tissue, storing many lymphocytes Survey the intestinal tract for pathogens

Bone Marrow Red marrow produces: B cells Natural killer cells Granulocytes(neutrophils, basophils, esinophils) Red blood cells and platelets Form through hematopiesis Some cells mature there and others migrate somewhere else and then mature

Helpful sites hill.com/sites/ /student_view0/chapter22/animation__the_immu ne_response.html hill.com/sites/ /student_view0/chapter22/animation__the_immu ne_response.html

Antibody Immunity Sequence Macrophage engulfs pathogens; wears antigens on surface Releases interleukin 1 to activate B cells B Cells become plasma cells Plasma cells release antibodies