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39 Cards in this Set
- Front
- Back
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Evolution of Immune Systems
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Our immune system protects us from harmful pathogens which can be many different types of organisms and
toxins. We will learn about two kinds of immunity: Innate Immunity and Adaptive Immunity. We will also learn about the organs, and systems associated with immunity. |
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Innate Immunity
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A host defense that can recognize common microbial invaders very quickly but shows no signs of an increased response upon repeated exposure to the same invader.
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Adaptive Immunity
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characterized by the production of a very large number of diverse receptors that are found on the surface of specialized white blood cells (B and T lymphocytes).
These receptors bind very specifically to molecules called antigens. This binding causes lymphocytes to divide and become much more numerous, resulting in characteristic features of adaptive immunity. |
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The Lymphatic System
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A system of vessels and organs that is closely associated with the cardiovascular and immune systems.
It has three main functions: 1). Lymphatic capillaries absorb excess tissue fluid and return it to the bloodstream. 2). In the small intestine, lymphatic capillaries called lacteals absorb fats in the form of lipoproteins And transport them to the bloodstream 3). The lymphoid organs and lymphatic vessels are the sites of production and distribution of lymphocytes, which help defend the body against pathogens |
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Lymphatic Vessels
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form one way system that begins with lymphatic capillaries, which are tiny closed-ended vessels. Lymphatic capillaries take up excess tissue fluid. Once inside the vessels, this fluid is known as lymph.
These merge with larger lymphatic vessels before entering the thoracic duct or the right lymphatic duct. Then on to the subclavian veins. |
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Primary Lymphoid organs
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Bone marrow, Thymus.
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Secondary Lymphoid organs
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are sites where some lymphocytes are activated by antigens
(lymph nodes, spleen) |
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Red Bone Marrow
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spongy, semisolid red tissue where hematopoietic stem cells divide and produce all types of blood cells, including lymphocytes. Two main kinds of lymphocytes: B lymphocytes (B-Cells) and T lymphocytes (T-Cells)
B-cells remain in red bone marrow and mature there but immature T-cell migrate to the thymus where they mature.. |
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Thymus
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soft bi-lobed organ located in the thoracic cavity between the trachea and the sternum, behind the heart. In the thymus, T-cells learn to recognize combnations of self-molecules and foreign molecules.
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Lymph Nodes
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small ovoid structures occurring along lymphatic vessels. Lymph nodes have areas called cortex and areas called medulla. As lymph fluid moves through these areas of each lymph node, resident phagocytes (varieties of white blood cells that ingest particles via phagocytosis) engulf pathogens and particles in the lymph. These phagocytes then “present” parts of these pathogens and debris to the T-cells.
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Spleen
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oval shaped secondary lymphoid organ with a dull purplish color. It is located on the upper left side of the abdominal cavity, behind the stomach. It contains a red colored “pulp” that filters and cleanses the blood.
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"Other"
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Other secondary lymphatic tissues are found in small patches around the body such as the tonsils, Peyer’s patches in the intestinal wall, and the vermiform appendix as some.
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Physical and Chemical Barriers
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Skin with the oil we call sebum acts as physical barrier against pathogens. The skin’s outer layer of keratinized cells forms a relatively impermeable barrier. Injury however, can breach this barrier and infection becomes an issue.
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Mucus
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traps pathogens for removal and is often associated with ciliated cells.
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Inflammatory Response
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A series of events that occur when damage to tissue occurs.
Four common signs of inflammation: redness, heat, swelling and pain. Most of these are due to capillary changes in the damaged area. |
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Histamines
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chemical mediators that are released by resident cells called mast cells. Mast cells are part of the innate immune system. Histamines cause the capillaries to dilate and become permeable which in turn allows proteins and fluids to escape into the tissues, resulting in swelling, along with increased blood flow which causes the warmth and redness. Other chemicals cause signals to be sent to the brain as pain.
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Neutrophils
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able to leave the blood stream and phagocytize bacteria in tissue.
• Have multiple ways of killing bacteria. • Cytoplasm is packed with granules that contain antimicrobial peptides and enzymes that can digest bacteria • Other enzymes generate free radicals such as superoxide and peroxides |
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Eosinophils
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can be phagocytic but are better known for mounting attack against animal parasites such as tapeworms.
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Macrophages
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longer lived phagocytic white blood cells that are found in all sorts of tissues. Engulfs pathogens and digest them into smaller molecular parts that are used to “educate” T-cells in the lymph nodes.
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Dendritic cells
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longer lived phagocytic white blood cells that are found in all sorts of tissues but most prevalent in the skin. Do a similar job to macrophages.
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Natural Killer Cells (NK)
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large granular lymphocytes that kill virus-infected cells and cancer cells by cell to cell contact. NK’s do their work while the adaptive defenses are still mobilizing. Produce cytokines.
• NK cells seek out cells that lack a particular type of “self” molecule called MHC-1. • NK cells induce these foreign cells to undergo apoptosis • NK cells do not undergo proliferations when exposed to particular antigen |
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Protective Proteins (Complement)
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a number of plasma proteins, produced mainly in the liver that “complement” certain immune responses.
• Must be activated by pathogens to exert their effects • Help to destroy pathogens in three ways: o Enhanced inflammation (they can bind to mast cells and trigger histamine release) o Increased phagocytosis ( some bind to surface of pathogens) o Membrane attack complexes(some complement proteins bind together to form a membrane attack complex that produce holes in the surface of some bacteria and viruses. Fluids and salts then enter the bacterial cell or virus to the point that it bursts.) |
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Interferons
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several different types of proteins. All are types of cytokines, soluble proteins that affect the behavior of other cells.
Most are made by virus-infected cells They bind to receptors of non-infected cells, causing them to produce substances that slow cellular metabolism and interfere with viral replication. |
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Adaptive Immune Defenses
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Adaptive defenses begin to respond while innate responses are fighting infection.
These defenses can recognize “self” from “non-self” and so are much more specific. Adaptive defenses usually take from five to seven days to become activated but can last for years (think vaccines!) also “acquired immunity”. Adaptive defenses depend primarily on B-Cells and T-Cells. Both cells can “recognize” and bind to antigens because they have antigen receptors on their plasma membrane. Pathogens, cancer cells, and transplanted tissues and organs bear antigens the immune system usually recognizes as non-self. A. B-Cells and Antibody-Mediated Immunity B-Cells: • Have receptor for antigen on surface called a BCR. • Usually activated in a lymph node or the spleen after BCR binds to a specific antigen • B-cell then divides by mitosis many times (clones of itself). Some become plasma cells others are Memory B cells. • Now there will be a lot of B cells that have the receptor for the particular antigens that the pathogen is giving off or has. • Clonal selection Theory states “ the antigen receptor of each B-cell or T-cell binds to only a single type of antigen” FIGURE (33.9 in new text) See steps in figure. This defense is known as Antibody-Mediated Immunity |
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Structure of Antibodies
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• Y shape molecules made of polypeptides
• Two heavy chains • Two light chains • On both types of chains have regions that are constant (C ) and regions that are variable (V) • Variable regions of antibody form the antigen binding sites. • Many classes of antibodies called immunoglobulin (Ig). • The class is determined by the structure of the antibody’s constant region • IgG, found in blood. IgA main class secreted in milk, tears, saliva and at mucous membranes. IgM are clusters of five Y-shaped molecules linked together. These are the first antibodies produced during most B-cell responses. IgE is found mainly bound to eosinophils and on mast cells in the tissues. |
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Monoclonal Antibodies
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(read text)
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T-Cells
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• Form in red bone marrow but finish development in thymus.
• Have a unique TCR similar to the BCR on B-cells. • Unlike B-Cells, T-Cells cannot recognize an antigen without help • The antigen must be “presented” to them by being attached to a MHC protein on the surface another cell. • Two types of T-cells: helper T-cells and Cytotoxic T-Cells • Helper T-Cells (TH cells) regulate adaptive immunity. Only recognize and respond to antigens presented on special APCs (antigen presenting cells) that have MHC II protein complexes. • Cytotoxic T-Cells (TC cells). Only recognize various cells with MHC I protein complex. • Helper T-cells secrete cytokines that affect B-cells , T-Cells and other cell types • Other Helper T-cells become memory T-cells. • Cell-mediated immunity, refers to the destruction or elimination of pathogens and other threats by Tc cells, macrophages, NK cells, or other cells. |
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Functions of Cytotoxic T Cells
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(see power point and text)
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HIV Infections (human immunodeficiency virus)
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this virus primarily infects helper T cells but can also infect macrophages. Is a retrovirus that mutates rapidly. Causes AIDS.
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Active Vs. Passive Immunity
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in general, adaptive immune responses can be induced actively or passively.
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Active Immunity
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occurs when an individual produces their own immune response against an antigen.
Example: A cold virus, you recover because the T-cell and B-cell responses that eventually clear the virus from your body. Active immunity can also be induced artificially via immunization with vaccines. |
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Passive Immunity
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occurs when an individual receives another person’s antibodies or immune cells.
This is a common natural process. Examples: nursing infants and across the placenta to fetus during pregnancy. Bone marrow transplant also is a form of passive immunity. |
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SCID (severe combined immunodeficiency) (Immunodeficiencies)
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Don’t have T cells or B cells or if have them, they are not functioning well enough to protect body from a variety of infections. 1 in 500000 births. Genetic.
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Allergies
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are hypersensitivity reactions to substances such as pollen, food, or animal dander/hair.
The responses to these antigens (allergens) usually includes some degree of tissue damage. |
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Immediate allergic reaction
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occurs within seconds of contact with allergen.
IgE antibody causes the response. IgE attached to mast cells and also to basophils and eosinophils In the blood. When allergen attaches to these cells, they release histamine and other substances that bring about the symptoms of an allergic reaction. |
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Anaphylactic shock
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Immediate allergic response that occurs after an allergen has entered the bloodstream. Characterized by sudden and life-threatening drop in blood pressure due to dilation of capillaries. Breathing may be affected as smooth muscle of bronchi constrict.
Injection of epinephrine can counteract this reaction until help can arrives. |
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Delayed allergic response
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initiated by memory T cells at the site of allergen contact in the body.
The allergic response is regulated by the cytokines secreted by these “sensitized” T cells at the site. Poison Ivy and TB skin test is a classic example of this. |
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Autoimmune Diseases
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immune system attacks self-tissue. Many autoimmune disease can develop after recovery from infection.
Examples: Lupus, Rheumatoid arthritis |
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Cytokines
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Therapeutic Agents
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