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Immunity and Disease Note .docx

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Natural Science
NATS 1670
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January 3 2012 - Immunity and Disease pp. 271 to 295 Three lines of defense protect the body 1. The body’s array of physical and chemical barriers to infection  Examples include intact skin and the linings of body cavities and tubes IMMUNE SYSTEM: a system of interacting white blood cells that defend the body o Known as a “cellular system” because the white blood cells perform most of the functions ANTIGEN: a molecule or particle that the immune system recognizes as non-self Triggers an immune response o Most are proteins, lipids or the large sugar molecules called oligosaccharides o All virus particles, foreign cells, toxins and cancer cells have antigens on their surface IMMUNITY: the body’s overall ability to resist and fight infections We are born with some general immune defenses and acquire other, specific ones 2. We are born with some pre-set responses to infection that are carried out by certain white blood cells and proteins in the blood o Triggered by chemical cues that are present on or in a variety of pathogens INNATE IMMUNITY: the body’s inborn, general defense against infection o Innate immune responses are general 3. ADAPTIVE IMMUNITY: a set of immune defenses that are tailored to the particular pathogens that enter the body o Triggered by innate immune responses o Changes as we go through life o Huge numbers of white blood cells mount a counterattack against the invasion o Adaptive responses can be mounted against a vast array of potential pathogens (they take about a week to develop but they leave behind cells that “remember” an antigen and protect against it for a long time Comparison of Innate and Adaptive Immunity Innate Immunity Adaptive Immunity Response Time Immediate 7 to 10 days How Antigen is Detected About 1000 pre-set Vast number of receptors receptors for specific antigens Triggers Non-self chemical cues on Antigens of pathogens, or in pathogens toxins, proteins on altered body cells Memory None Long-term White blood cells and their chemicals are the defenders in immune responses - White blood cells operate in both the innate and adaptive immune responses (all release substances that help muster or strengthen defense responses) CYTOKINES: signalling chemicals released by cells of the immune system, they promote and regulate many aspects of immunity Circulate in the blood:  NEUTROPHIL: phagocyte that follows chemical trails to infected, inflamed, or damaged tissues o Make up 2/3 of white blood cells that circulate in blood  EOSINOPHILS: white blood cells that targets large parasites, such as worms o Also play a part in allergies  BASOPHILS: circulating white blood cell, and release substances from their granules that cause inflammation Perform their functions while in tissues:  MAST CELLS: white blood cell in many tissues, and have granules that release substances causing inflammation  MACROPHAGES: phagocytic white blood cell in tissue fluid  DENDRITIC CELLS: phagocytic white blood cell o Alert the adaptive immune system when they detect antigens LYMPHOCYTES: B cells, T cells, and other white blood cells that are active mainly in tissues and organs of the lymphatic system  B CELLS: B lymphocyte. Cells derived from them make antibodies  T CELLS: T lymphocyte. T cells target abnormal body cells, among other roles in adaptive immunity The lymphatic system LYMPHATIC SYSTEM: organs and tissues that return tissue fluid to the cardiovascular system and have roles in defenses LYMPH: the tissue fluid that moves in lymph vessels - Tonsils – defense against bacteria and other foreign agents - Right lymphatic duct – drains right upper portion of the body - Thymus gland – site where certain T lymphocytes acquire means to chemically recognize specific foreign invaders - Thoracic duct – drains most of the body - Spleen – major site of antibody production; disposal site for old red blood cells and foreign debris; site of red blood cell formation in an embryo - Some lymph vessels – return excess tissue fluid and reclaimable solutes to the blood - Bone marrow – red marrow in some bone is where whit blood cells are produced The lymph vascular system functions in drainage, delivery, and disposal LYMPH VASCULAR SYSTEM: lymph capillaries and other vessels of the lymphatic system o They collect water and dissolved substances from tissue fluid and transport them to ducts of the cardiovascular system o The system starts at capillary beds where fluid enters the lymph capillaries through valves that are areas where endothelial cells overlap. The capillaries then merge into lymph vessels that have smooth muscle and valves that prevent backflow. Then they converge into collecting ducts that drain into veins in the neck. o Movement of skeletal muscles and the rib cage help move the fluid Lymphoid organs and lymphatic tissues are specialized for body defense LYMPH NODES: organs of the lymphatic system that filter lymph; they are located an intervals along lymph vessels o It has several chambers where white blood cells accumulate after they have been produced in bone marrow. o Becomes a battleground between lymphocytes and foreign agents during infection SPLEEN: lymphoid organ that filers blood and serves as a reservoir for lymphocytes o It has chambers filled with soft red and white tissue called “pulp” (red pulp is storage reservoir of red blood cells and macrophages, white pulp is masses of lymphocytes) THYMUS: lymphoid organ where T cells multiply and mature Barriers to infection - In females, lactate produced by Lactobacillus bacteria in the vagina help maintain a low pH level that most fungi and bacteria cannot tolerate - The inner walls of the respiratory airways are coated with sticky mucus that contains lysozymes (enzymes that chemically attack and help destroy many bacteria) - Lysozyme in tears, saliva, and gastric fluid offer protection - Urine’s low pH help flush out bar pathogens from the urinary tract - In adults, mild diarrhoea can rid the lower GI tract of pathogens Innate Immunity COMPLEMENT SYSTEM: a set of inactive proteins in blood and tissue fluid; the proteins are activated as part of innate immunity o They are inactive until one makes contact with a pathogen. The interaction unleashes a bunch of reactions that activate even more complement proteins until the molecules flood a damaged area. o Activated complement attracts phagocytic white blood cells which blankets the pathogen with a “complement coat”, which makes it easier to engulf and kill o Some complement proteins form a MEMBRANE ATTACK COMPLEX: structure formed that punctures bacteria, which then die - When a pathogen enters the body, macrophages in tissue fluid are the first defenders. They engulf and destroy anything other than healthy body cells. If it detects an antigen, it releases cytokines that attract more macrophages and other white blood cells - Activated complement and cytokines cause INFLAMMATION: a general response to tissue damage. Symptoms are warmth, redness, swelling and pain HISTAMINE: chemical released by mast
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