biol 216 14 Immune System 49-96.pdf

biol 216 14 Immune System 49-96.pdf - V(D)J recombination...

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6/1/17 1 V(D)J recombination V(D)J recombination is the unique mechanism of genetic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation. It involves somatic recombination, and results in the highly diverse repertoire of antibodies/immunoglobulins (Igs) and T cell receptors (TCRs) found on B cells and T cells 49 50 Clonal Selection Theory n Clone: each genetically unique line of lymphocytes arising from the gene segment rearrangement n Millions of genetically different clones of T and B cells are generated… each clone responds to 1 specific antigen n T and B cells then migrate to lymphoid tissues 51
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6/1/17 2 B and T Cell Development 52 Thymus A specialized organ of the immune system where T lymphocytes mature. Each T cell attacks a specific foreign substance which it identifies with its receptor. T cells have receptors which are generated by randomly shuffling gene segments. Each T cell attacks a different antigen. T cells that attack the body's own proteins are eliminated in the thymus. 53 Clonal Selection Theory Summary 1) A hematopoietic stem cell undergoes differentiation & genetic rearrangement to produce immature lymphocytes (2) with many different antigen receptors 3) Those that bind to antigens from the body’s own tissues are destroyed. The rest mature into inactive lymphoctyes (4) Those that encounter a matching foreign antigen (5) are activated to produce many clones of themselves (6) Note: Hematopoietic stem cell: give rises to all the other blood cells through the process of haematopoiesis. located in the red bone marrow 54
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6/1/17 3 II. Immunoglobulins n Large glycoprotein molecules n Serve as both: n Antibodies (also known as Ig: immunoglobin; are secreted by plasma cells, which are white blood cells that are derived from B cells and secrete large volumes of antibodies) n The specific receptors of B cells 55 Simplified structure of Ig V=variable region C=constant region 56 Antigen Binding Receptors are on B Cells and T Cells IgD: Membrane receptor for mature B cells 57
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6/1/17 4 Immunoglobins: FiveClasses of Antibodies 58 Allergy is a hypersensitivity disorder of the immune system. Symptoms include red eyes, itchiness, and runny nose, eczema, hives, or an asthma attack occur when a person's immune system reacts to normally harmless substances in the environment (allergen). Allergic reactions are distinctive because of excessive activation of certain white blood cells (mast cells, basophils, which produce histamine) by a type of antibody: immunoglobulin E (IgE). result in an inflammatory response which can range from uncomfortable to dangerous.
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