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The Body’s Defense System Chapter 14 Lymphatic and Immune System Nonspecific Defenses Function of the Immune system defend the human body against dangerous enemies Harmful bacteria, viruses, fungi, and protists Pathogens: Disease causing agents Lines of Defense Innate immunity (aka active) (lines 1 & 2) – include physical barriers between the outside world and inside of body, inflammatory responses, immune proteins, and WBC’s Acquired Immunity (line 3) – building resistance to a specific pathogen First line of Nonspecific Defense Body’s surface defenses are nonspecific Skin is an impenetrable barrier to invading pathogens Oil and sweat inhibit the growth of pathogens. Sweat has an enzyme called lysozyme that digests bacterial walls and kills the bacteria. Body’s internal surface uses Mucous Membranes Layers of epithelial tissue that produce a sticky, viscous fluid Lines nasal passages, lungs, respiratory passages, and reproductive tract Carried to the stomach for digestion Second Line of Nonspecific Defense (Innate) Injury or local infection like a cut can cause Inflammatory Response: Series of events that suppress infection and speed recovery Histamine: Causes local blood vessels to dilate, blood flow to the area & WBC’s Temperature Response Fever Temperature rises to fight against invading pathogens Higher temperatures are harmful to many bacterial pathogens Over 103° can destroy body’s cellular processes (destroy enzymes Over 105° can be fatal Destroys cells Second Line of Nonspecific Defense Immune Proteins Complement System: 20 different proteins circulate in the blood and become active when they encounter pathogens Form a ring-like structure called a membrane-attack complex around the pathogen poking holes in the pathogen’s cell membrane= death Interferon: A protein released by cells infected with viruses Cause nearby cells to produce an enzyme that prevents viruses from making viral proteins and RNA. White Blood Cells (AKA phagocytes) Neutrophils: Macrophages: WBC that engulfs and destroys pathogens, suicide bomber Ingest and kill pathogens they encounter Natural Killer cells: Large WBC that attacks cells infected with pathogens Cells Involved The third line of defenses is specific 4 Main kinds of WBC’s that participate in the immune response Macrophages Cytotoxic T cells: Attack and kill infected cells B cells: Label invaders for later destruction by macrophages May become plasma cells (release antibodies to disable specific pathogens or memory cells (WBC Cops!) Helper T cells: Activate both T and B cells Recognizing Invaders An infected body cell will display antigens of an invader on its surface Antigen: Substance that triggers an immune response. Immune Response Parts B cell response is a passive defense that aids in the removal of pathogens. T cell response is an active cell-mediated defense that involves the destruction of pathogens by cytotoxic T cells. Steps of an Immune Response When a virus infects a cell, the cell displays viral antigens on its surface. Macrophages engulf and destroy viruses and also display viral antigens. Helper T cells bind to antigens on the macrophages and they (macro) release interleukins. Interleukins make Helper T cells activate Cytotoxic T and B cells. Steps Continued B cells divide and turn into plasma cells Plasma cells make antibodies that bind to viral parts and to infected cells and mark them for death. Macrophages engulf and destroy the “marked” viral parts and infected cells. Cytotoxic T cells also destroy infected cells that are marked. Some B cells become memory cells that will immediately destroy the virus if it tries to invade the body again. Disease Transmission and Prevention Diseases are transmitted in 5 different ways Person to person contact Air Food Water Animal bites Resistance to Disease Immunity: Resistance to a particular disease Vaccination: Medical procedure used to produce immunity Vaccine: A solution that contains a dead or modified pathogen that can no longer cause disease Antigen Shifting: Subsequent exposure to a virus causes the body to make new antibodies. Disorders of the Immune System In some people, the immune system can not distinguish between the body’s antigens and foreign antigens. Autoimmune disease: The body launches an immune response against its own cells, attacking body cells as if they were pathogens. Examples: Graves Disease Multiple Sclerosis Type 1 Diabetes HIV and AIDS HIV, the virus that causes AIDS, infects helper-T cells HIV: Human immunodeficiency virus AIDS: Acquired immunodeficiency syndrome HIV is contracted through sexual contact, blood transfusions, and contaminated needles (drug users, tattoos, piercing) HIV infects cells by using proteins on its surface attach to the host cell (helper-T cells) The HIV virus infects only a few cells at time, so it takes a long time to show symptoms.
