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Chapter 22

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Department
Biology
Course
Biology 1225
Professor
Michael Butler
Semester
Fall

Description
Chapter 22 Immunity 22.2 Integrated Responses to Threats pg 429 ***Innate immunity – all of the inborn general and non specific defenses against infection. ***adaptive immunity – in vertebrates, set of immune defenses that can be tailored to specific pathogens encountered by an organism during its lifetime. Antigen – a molecule or particle that the immune system recognizes as non self. Triggers an immune response *** A molecule that is recognized by the body as foreign is called an antigen*** Immunity – the body’s ability to resist and fight infections B cell – B lymphocyte. Lymphocyte that can make antibodies T cell – T lymphocyte. Lymphocyte central to adaptive immunity; some kinds target infected or cancerous body cells NK Cell (natural killer cell) – ***the function of the NK cell is to kill virus infected cells of the body*** Dendritic cell –phagocytic white blood cell that alerts the immune system to the presence of antigen in solid tissues Macrophage – phagocytic white blood cell that patrols tissues and tissue fluids ***macrophages are the white blood cell type to most often first encounter a pathogen*** 1 What is immunity? 1. The body’s ability to resist and fight infections is called immunity 2. Innate Immunity is a system of immediate, general defenses against a fixed number of antigens that can prevent pathogens from becoming established in the body. A microorganism or other antigen-bearing agent that breaches surface barriers triggers Innate immunity - of multi celled organisms 3. Vertebrate adaptive immunity is a system of defenses that can specifically target billions of different antigens 4. ***Inappropriate immune responses that target our own cells are called autoimmune*** 2 Three lines of defenses (adaptive immunity/innate immunity) - the mechanisms of adaptive immunity evolved within the context of innate immunity - The two systems were once thought to operate independently of each other, but we now know they function together. - Both systems together are described in terms of three lines of defenses 1. the first line of defense includes the physical, chemical and mechanical barriers that usually keep pathogens on the outside of the body. Example: a physical barrier to infection is mucus and the sweeping action of cilia that keep pathogens from getting inside airways to the lungs. Bacteria and other particles get stuck in mucus secreted by goblets cells. Cilia or other cells sweep the mucus to the throat for disposal 2. The second line of defense is Innate immunity which begins after a tissue is damaged or after an antigen is detected inside the body. Its general response mechanisms quickly rid the body of many invaders. An innate immune response triggers adaptive immunity 3. The third line of defense is adaptive immunity – white blood cells divide to form huge populations that target a specific antigen and destroy anything bearing it. Some white blood cells that form during an adaptive response persist after infection ends. If the same antigen returns, these memory cells mount a secondary response. 3 White Blood Cells ***White blood cells carry out the immune response *** White blood cells have a critical role in both innate immunity and adaptive immunity ***Lymph Nodes filter bacteria*** ***White Cells are packed inside lymph found in the lymphatic system and these often swell during infection*** White blood cells are central to both systems; signalling Complement and signalling molecules such as cytokines which help coordinate the activities of white blood cells such as phagocytic dendritic cells and macrophages - Different types of white blood cells are specialized for specific tasks 1. PHAGOCYTIC WHITE BLOOD CELLS - engulf and digest pathogens, dead cells or other particles: a. Neutrophils, which circulate in blood are the most abundant phagocytes. b. Macrophages that migrate through tissues and tissue fluids develop from monocytes, which patrol the blood ***macrophages are the white blood cell type to most often first encounter a pathogen*** c. Dendritic cells are phagocytes that alert the adaptive immune system to the presence of antigen in solid tissues. 4 2. Lymphocytes (B cells, T cells and NK cells) are white blood cells with special roles in immune responses ***form in the bone marrow A. *** T cells – T lymphocyte. Lymphocyte central to adaptive immunity; some kinds target infected or cancerous body cells: there are several kinds: cytotoxic T Cells and helper T Cells i. Cytotoxic T cells that can kill infected or cancerous body cells ii. Helper T cells The T helper cell is the white blood cell that is the controlling agent of much of the immune response, it is the “director-general” – it is tragic that it is the very cell (the T helper cell) that is needed to control an immune response to a virus that is infected by the HIV AIDS virus. iii. T cells mature and differentiate in the thyroid/thymus gland B. B cells – B lymphocyte. Lymphocyte that can make antibodies i. ***synthesize antibodies when they are mature*** ii. differentiate in the bone marrow iii.***When a B cell binds to an antigen it undergoes mitosis and multiplies*** C. NK cells(natural killer cells) – ***function is to kill virus infected cells of the body ***- kills cancerous body cells undetectable by cytotoxic T cells. 5 22.3 pg 430 First Line of Defense – Surface Barriers Lysozyme – antibacterial enzyme that occurs in body secretions such as mucus Normal flora – microorganisms that typically live on human surfaces, including the interior tubes and cavities of the digestive and respiratory tract ***microorganisms such as normal flora on skin can cause serious illness if they enter the body via injuries ***Consist of Fungi, bacteria and Protozoa*** What prevents ever present microorganisms from entering the body’s internal environment? 1. ***The first line of defence against microbes is external barriers***. Vertebrates fend off pathogens at body surfaces with physical, mechanical and chemical barriers (including lysozyme – antibacterial enzyme) against harmful microorganisms, cancer cells and other harmful agents. 2. Surface barriers usually keep microorganisms that contact or inhabit body surfaces from invading the internal environment 3. Normal flora deter more dangerous microorganisms from colonizing the body’s internal and external surfaces i. Most normal flora that colonize body surfaces (including the linings of tubes and cavities of the digestive and respiratory tracts) do not cause disease unless they penetrate inner tissues ii. the skin is a surface barrier - a thick waterproof layer of dead cells that usually keeps normal skin flora from penetrating internal tissues. iii. Mucus, lysozyme and often the sweeping action of cilia is another surface barrier that protects the linings of internal tubes and cavities of the digestive and respiratory tract from normal flora *** Blood and tissue fluids are generally sterile 6 22.4 The Innate Immune Response / Non specific immune response pg 432 ***Innate immunity – all of the inborn general and non specific defenses against infection*** Second Line of Defense – Innate Immunity Complement – a set of proteins that circulate in inactive form in blood and when activated play a role in immune responses. fever – an internally induced rise in core body temperature above the normal set point as a response to infection or tissue damage inflammation – a local response to tissue damage or infection; characterized by redness, warmth swelling and pain 7 Innate Immune Response/Non Specific Immune Response: A second line of defense –the fast acting general mechanisms of innate immunity (second line of defense)– can keep an invading pathogen from establishing a population in body tissues and fluids *** Innate immunity includes or the non specific immune response*** 1. Complement system 2. Phagocytic white blood cells 3. Fever 4. inflammation 1. Complement - An innate immune response can be triggered by activated complement or by phagocytic white blood cell which engulf a pathogen or other antigen bearing particle. ***Complement proteins a. a set of proteins (about 30) that circulate in inactive form in blood and interstitial fluid and when activated play a role in immune responses b. The complement become activated when they en
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