The Immune System and Disease Copy everything in RED

Diseases Disease = any change, other than injury, that disrupts the normal functions of the body Diseases can be inherited (ex. Hemophilia) Diseases can be caused by materials in the environment (ex. Cigarette smoke) Diseases can be produced by agents (ex. Bacteria, viruses, fungi) = pathogens Pathogens = “sickness-makers” Diseases caused by pathogens = infectious diseases, because they enter, or infect, the body

Agents of Disease The human body provides great conditions for pathogenic growth You have many different microorganisms living in your body that are actually harmless or beneficial However, some microorganisms are dangerous Some bacteria break down body tissues and others release toxins (poisons) Some protists, fungi, and worms are parasites that live inside you and use up your nutrients or destroy blood/nerve cells Viruses are nonliving pathogens that use a host cell to make copies of the virus and destroy other cells

Spreading Infectious Diseases Infectious diseases are spread From person to person: coughing, sneezing, or physical contact Common cold, mumps, measles, influenza, STDs (AIDS), meningitis, athlete’s foot Contaminated water and/or food Cholera, dysentery, E.coli infection, salmonellosis Vectors: infected animals (ticks/mosquitoes) Lyme disease, malaria, West Nile virus, rabies

Agent That Causes Disease Method of Transmission Figure 40–3 Pathogens and Disease Copy pathogen type, disease and method of transmission Section 40-1 Pathogen Types Disease Agent That Causes Disease Method of Transmission Common cold Rhinovirus Two types (A, B), plus subtypes Varicella Paramyxovirus Mycobacterium tuberculosis Neisseria meningitidis Vibrio cholerae Clostridium tetani Trypanosoma Plasmodium Entamoeba histolytica Schistosoma Taenia saginata Imperfect fungi Airborne; direct contact with infected person Airborne; droplet infection; direct contact with infected person Droplets in air; direct contact with secretions of infected person Droplets in air; contaminated milk and dairy products Direct contact with a carrier Contaminated drinking water Contaminated wound; usually puncture wound Spread by tsetse fly Spread by Anopheles mosquitoes Freshwater streams and rice paddies Contaminated meat Contact with infected person Exchange of hats, combs, or athletic head gear with infected person Viruses Influenza Chicken pox Measles Bacteria Tuberculosis Meningitis Cholera Tetanus Protists African sleeping sickness Malaria Amoebic dysentery Worms Schistosomiasis Beef tapeworm Fungi Athlete’s foot Ringworm

Fighting Infectious Diseases Drugs have been developed to use against pathogens Antibiotics = chemicals that kill bacteria without harming the cells of humans or animals Penicillin = interferes with the synthesis of cells walls by Eubacteria (breaks down peptidoglycan in their cell walls) Streptomycin = interferes with bacterial growth by blocking protein synthesis in ribosomes Antivirals = inhibit the ability of viruses to invade cells or multiply inside cells

The Immune System A series of defenses that guard against diseases = body’s protection Nonspecific defenses = “walls” of the immune system keeping everything out Specific defenses = “security guards” identifying and inhibiting pathogens

Nonspecific Defenses Skin = most important nonspecific defense Physical barrier Acidic environment on surface kills bacteria Mucus, sweat, tears and saliva Traps pathogens and removes them from the body by cilia or destroys them using the enzyme lysozyme, which breaks down cell walls Inflammatory response = reaction to tissue damage caused by injury or infection Blood vessels around wound expand, white blood cells enter infected tissue and phagocytes (special WBCs) engulf and destroy bacteria, tissue becomes swollen and painful, body temperature ingrowth and increase circulation and activity of WBCs Interferon = proteins that “interfere” with the virus creases (fever) to slow pathogen Proteins released by virus-infected cells to help other cells resist viral infection by inhibiting viral protein synthesis, blocking viral replication

Specific Defenses Pathogen: any disease causing agent Antigen = a substance that triggers the immune response (organic molecules on the surface of pathogens) Antigens are chemicals present on the surface of viruses, bacteria, pollen grains etc. Antibody = protein that helps destroy pathogens by binding to antigen and attracting phagocytes to engulf and destroy them

Humoral Immunity Immunity against pathogens in the body fluids (blood/lymph) Immunity produced by lymphocytes (type of WBC) B lymphocytes (B cells) produce antibodies to mark pathogens and prevent future infections

Cell-mediated Immunity Immunity that relies on lymphocytes (cells) Killer T cells (cytotoxic T cells) can attack infected cells and destroy their cell membranes Killer T cells are what make organ transplants difficult, because they see the new organ as foreign and begin to attack it = rejection.

Permanent Immunity People that survived infectious diseases, never developed the same disease again Memory B and T cells remain capable of producing specific antibodies to that pathogen, ensuring the disease never gets a chance to develop again

Active Immunity An immediate active immune response against the pathogen in a vaccine Vaccination = injection of a weakened or mild form of a pathogen to produce immunity Prevents serious human diseases by stimulating the immune system to create plasma cells capable of producing the specific antibodies for another possible infection Active Immunity lasts long term (permanent)

Passive Immunity Antibodies produced by other animals for a pathogen are injected into the bloodstream The antibodies will produce passive immunity against a pathogen as long as they remain in circulation (several weeks) Antibodies from the mother are passed to the fetus through the placenta or to the infant in the mother’s milk = maternal immunity The antibodies will produce passive immunity against most infectious diseases for the first few months of life or longer if breast-fed

Immune System Disorders Although the immune system defends the body from potential pathogens, sometimes disorders occur The immune system may overreact to an antigen, producing discomfort or disease The cellular nature of the immune response is a potential weak point

Allergies Overreaction of the immune system Allergies occur when antigens from allergens (pollen, dust, dust mites) bind to mast cells (type of immune cell common in nasal passages) Activated mast cells release chemicals = histamines, which increase the flow of blood and fluids to the surrounding area (sneezing, runny eyes/nose, etc) Antihistamines = drugs used to reduce allergy symptoms by counteracting the effects of histamines Asthma = allergic reaction where smooth muscle contractions reduce the size of air passageways in the lungs making breathing difficult

Autoimmune Disease The immune system has the ability to distinguish “self” from “nonself” The immune system makes a mistake and attacks the body’s own cells (“it attacks itself”) Juvenile-onset diabetes (immune system attacks insulin-producing cells in pancreas) Myasthenia gravis (attacks neuromuscular junctions) Multiple Sclerosis (destruction of myelin sheath – attacks nervous system) Lupus (attacks cells and tissues resulting in inflammation and tissue damage: heart, joints, skin, lungs, blood vessels, liver, kidneys and nervous system)

AIDS Acquired Immune Deficiency Syndrome (AIDS) = when cells of the immune system are weakened by infection Caused by HIV (human immunodeficiency virus) and spread by contact with body fluids (drug needles, unprotected sexual intercourse, breast milk, blood during birth, blood transfusions) HIV attaches and destroys most helper T cells, so body is more susceptible to infections People DO NOT die from HIV/AIDS, they die from the infections they get because the HIV virus has left their immune system unable to respond to the infections

Cancer Cancer is caused by defects in the genes that regulate cell growth and division Inherited genes Viruses: interfere with cell cycle (mitosis) Ex. Human papilloma virus (HPV: an STD) can lead to cervical cancer or genital warts (non cancerous) Radiation: causes mutations in DNA Ex. X-rays, nuclear radiation, sunlight (UV Rays) Chemicals: cause mutations in DNA Carcinogens = chemicals that cause cancer Ex. Chloroform and benzene (industrial solvents used in production of drugs, plastics and synthetic rubber, small component in gasoline), cigarette smoke

Blood Antigens and Antibodies DRAW this chart!