Class Notes, week of 03/21
Class Notes, week of 03/21 BSC 2023
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This 8 page Class Notes was uploaded by Eleonora Sacks on Monday March 28, 2016. The Class Notes belongs to BSC 2023 at Florida International University taught by Paul Sharp in Spring 2016. Since its upload, it has received 15 views. For similar materials see Human Biology in Biology at Florida International University.
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Date Created: 03/28/16
Class notes: week of 03/21 3/28/16 4:59 PM Immunity and Lymphatic system: • Lymph organs: organ of lymphatic system other than lymphatic vessels 1. Primary: red bone marrow and thymus gland 2. Secondary: lymph nodes, spleen, tonsils, appendix and Peyer's patches • Red bone marrow: produces red blood cells, like: • Leukocytes (allergies, especially pollen): neutrophils (phagocytosis), eosinophils and basophils (both degranulate, throw chemicals at things that shouldn't be in the body). These are like the "common people in the castle" • Lymphocytes: B cells (mature in bone marrow and produce antibodies), T cells (mature in thymus), natural killer cells. These are like the "military, king's guard". • Thymus: involved in the maturation of T cells, only about 5% pass autoreactivity test. Located between the trachea and the sternum superior to the heart. • Spleen: stores and filters blood; macrophages phagocytose pathogens and debris. Largest lymphatic organ • Lymph nodes: mass of lymphatic tissue located along the course of a lymphatic vessel, macrophages phagocytose pathogens and debris. • Tonsils: patches of lymphatic tissue, first to encounter pathogens • Peyer's patches: lymphatic tissue located within the appendix and encounters pathogens. • Autoimmune disease: when your own body attacks itself. The thymus is responsible so that this doesn't happen. • One of the functions of the lymphatic vessel is to pick up what the circulatory system leaks out: • Immune system: • Functional system whose components attack foreign substances or prevent their entry to the body 1. Innate immunity: skin, mucous membranes. A mechanism of defense that doesn't depend on prior exposure to the invader, nonspecific (broad) (the skin protects against everything). Immediate. • First line of defense: o Skin: layer of protection associated with the innate immunity system. Like the castle wall. Oil and sweat glands give skin surface pH of 3-5, sweat contains lysozyme (digests bacterial cell wall), normal flora include non-pathogenic bacteria and fungi, epidermis 10-30 cells thick and dermis 15-40 times thicker. o Mucous membranes: 1. Digestive tract: saliva contains lysozyme (also found in tears), acidic environment of stomach pH of 1.5-3.5, digestive enzymes in intestine, nonpathogenic normal flora, vomiting and diarrhea may expel pathogens. 2. Respiratory tract: pathogens trapped by mucus in bronchi and bronchioles, ciliated epithelial cells sweep mucus toward the glottis, coughing and sneezing expels pathogens. 3. Urogenital tract: vaginal secretions viscous and acidic, secretions promote growth of normal flora, acidic urine of both sexes may wash out pathogens. 2. Adaptive (acquired) immunity: specific to the particular non-self material, requires time for development, occurs more quickly and vigorously on secondary response. Class notes: week of 03/21 3/28/16 4:59 PM • Second line of defense: phagocytes, inflammation, complement and interferon, chemical signals: • Recognize a wide spectrum of pathogens without a need for prior exposure • Key players include neutrophils, monocytes that become macrophages • These cells phagocytose pathogens and trigger the release of cytokines (chemical signals, protein hormones that let other immune system "soldiers" or cells where the problem is) • Results in inflammation and specific immune responses • Inflammation: occurs over seconds, minutes, hours and days o Histamine: chemical that dilates blood vessels o Bradykinins: make the spaces that make the blood vessels leaky even larger so there is more leakage o Prostaglandins: responsible for the pain (eg: sunburnt skin pain) 1. Dilation of blood vessels increases blood flow at site (RED & WARM) 2. Increased permeability of capillaries causing edema (tissue SWELLING). This allows the cells to move to the site of the harm quicker. 3. Tissue swelling puts pressure on nerve endings (PAIN and potential loss of function) 4. Macrophages and neutrophils release cytokine tumor necrosis factor (TNF) which acts on hypothalamus to raise the body temp (fever) 5. Cell death (necrosis) always occurs to some degree during inflammation • Complement: 30 proteins that are produced by the liver. They circulate freely in blood plasma. When activated, one forms a domino effect on another causing a cascade of events that form a membrane attack complex (MAC) that form pores in pathogens that have lipid membrane to induce lysis (causes the bad bacteria to explode by making holes in its membrane) • Interferon: antiviral agent produced by an infected cell that blocks infection of an uninfected cell (degrades RNA and blocks protein production). It works especially with virus. Type of cytokine. • Cytokines: protein hormones used by immune cells to communicate. Can affect same cells that produce them, cells nearby or cells distant in body. EG: interferon. • • • Third line of defense: ADAPTIVE IMMUNITY • Important aspects of the immune response: 1. Non-self recognition: ability to distinguish self-antigens from non-self § Antigen: foreign substance that stimulates and immune response. EG: dust, pollen § Antibody: protein produced in response to the presence of an antigen 2. Antigen-specific: recognizes and is directed against specific antigens 3. Systemic response: immunity is not restricted to initial infection site 4. "Memory": recognizes and mounts stronger attack on previously encountered pathogens. • Major histocompatibility complex (MHC): cell surface glycoproteins, polymorphic. Think of them as flag poles on the surface of cells. Only T cells can decipher them. 1. MHC class 1 protein: found in eukaryotes (cells that have nucleus), has cytotoxic T cells (CD8) respond to endogenous antigen (generated inside the cell) bound to MHC class 1 protein. The CD8 is the only cell that understands the signal. When the CD8 connects with an infected cell and realizes that something is wrong, it produces cytokines that communicate with the infected cell through its own cytokines which cause the CD8 to clone itself and attack the infected cell until it causes apoptosis (to explode) Class notes: week of 03/21 3/28/16 4:59 PM • MHC class 2 protein: • Found only on professional antigen presenting cells like Macrophages and B cells • Helper T cells (CD4) respond to exogenous antigen (comes from outside the cell) bound to MHC class 2 proteins • When bacteria is engulfed by macrophages, the Helper T cell connects with the macrophages, then clones itself, and then has 2 choices: to produce a humoral response (communicates with a B cell that clones and the "general" (CD4) signals them to fire their arrows towards the infected cell) or a cellular response (it "juices up" the macrophage and destroys the bacteria) • Two overlapping arms of immunity: • Cell-mediated immunity: (like hand to hand combat), associated with cell surfaces, T-cell receptors that are unable to see free antigens o T cells: 2 main types that include CD8 (directly attack cells that carry specific antigens) and CD4 (regulate immune responses of other cells, they are like the "general" during battle) § Produced in red bone marrow, they migrate to the thymus to mature and be selected § T cell receptors recognize antigen presented on self MHC molecules • Humoral immunity: (like archers shooting arrows), based on antibodies on cell surfaces and in body fluids (blood, lymph, etc). o B cells: bind to specific antigen with its antibody (B cell receptor) and also serve as antigen presenting cell to Helper T cells. They are produced in red bone marrow. Immunoglobulin synthesis happens in bone marrow. Tested for accuracy in red bone marrow as well. Types: § Plasma B cells: are large B cells that have been exposed to antigen, they produce and secrete large amounts of antibodies, are short lived cells that undergo apoptosis § Memory B cells: are specific to the antigen encountered, they live for a long time and can respond quickly following a second exposure to the same antigen. • HIV (Human immunodeficiency virus): a retrovirus that attacks the body's immune system, causes AIDS. • HIV mounts direct attack on TH cells by binding to CD4 proteins on cell surface • HIV kills TH cells faster than they can proliferate over time • When CD4 and T cell numbers decline bellow 200 cells per microlitre of blood, the cell mediated immunity is lost.
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