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UT Arlington BIOL 1282 - Lecture 8 - Immune System

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Slide 1Slide 2Slide 3Innate immunity in vertebratesInterferon – protein that serves as alarm signalSlide 6Inflammation – “setting on fire”The lymphatic system is important to fight infectionsLymphatic organs are a major battleground during infectionSlide 10Slide 11The adaptive immune response counters specific invadersSlide 13Lymphocytes mount a dual defenseLymphocytes mount a dual defenseSlide 16Lymphocytes mount a dual defenseSlide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Antibodies mark antigens for eliminationSlide 27Major Histocompatibility ComplexSlide 29Slide 30Cytotoxic T cells destroy infected body cellsSlide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Biology 003: Organisms in Their EnvironmentLecture #8 – Immune SystemPhoto by Sarah WolakFigure 24.1AInnate immunity (24.1–3)The response is the same whetheror not the pathogen has beenpreviously encounteredAdaptive immunity(24.4–15)Found only invertebrates; previousexposure to thepathogen enhances theimmune responseExternalbarriers (24.1)Internaldefenses (24.1–2)The lymphatic system (24.3)• Antibodies (24.8–10)• Lymphocytes (24.11–13)• Phagocytic cells• NK cells• Defensive proteins• Inflammatory response (24.2)• Skin/ exoskeleton• Acidic environment• Secretions• Mucous membranes• Hairs• CiliaINNATE IMMUNITYInnate immunity is a series of defenses that–act immediately upon infection–are the same whether or not the pathogen has been encountered before.Invertebrates rely solely on innate immunityInnate immunity in vertebratesVertebrate innate immunity includes–Barriers: skin, tracheal cilia–Interferons: proteins produced by virus-infected cells, that help to limit the cell-to-cell spread of viruses–Phagocytic (“cell eater”) cells (white blood cells)–Neutrophils (most abundant WBC in mammals)–Macrophages are large phagocytic cells–Natural killer cells: attack virus-infected cells–Complement system - a group of about 30 kinds of proteins; creates membrane attack complex in bacteriaViral nucleic acidVirusmRNADNAInterferongenesturn onInterferon stimulatescell to turn on genesfor antiviral proteinsAntiviral proteins blockviral reproductionNewvirusesInterferonmoleculesMakes interferon;is killed by the virusIs protected against the virusby interferon from cell 1Host cell 1 Host cell 234215Figure 24.1BInterferon – protein that serves as alarm signalMacrophage ingesting bacteriaNeutrophil attacking bacteriumPhagocytic White Blood CellsInflammation – “setting on fire”Tissue damage triggers the inflammatory responseTissue injury; signalingmolecules, such as histamine,are released.Dilation and increased leakiness oflocal blood vessels; phagocytesmigrate to the area.Phagocytes (macrophages andneutrophils) consume bacteria andcellular debris; the tissue heals.Blood vesselWhite blood cellSignalingmoleculesBacteriaPinSkin surfaceSwellingBlood clotPhagocytes andfluid moveinto the areaPhagocytes21 3Figure 24.2The lymphatic system is important to fight infectionsThe lymphatic system is–involved in innate and adaptive immunity–network of lymphatic vessels that collect fluid from body tissues–similar to veins, including 1-way valves–lymph is returned to the blood•lymph organs (e.g. lymph nodes, spleen, tonsils)–packed with white blood cellsLymphatic organs are a major battleground during infectionThe lymphatic system collects–microbes from body tissuesTransports microbes to lymph nodes and organs–macrophages engulf the invaders–lymphocytes (WBCs) mount an adaptive immune responseResults in “swollen glands”–filling of lymph nodes with defensive cellsThe Lymphatic SystemLymphatic organs are indicated in pinkADAPTIVE IMMUNITYOur immune system responds to foreign molecules called antigens, which elicit the adaptive immune response.–antigens are antibody generating moleculesThe adaptive immune system–is found only in vertebrates–“remembers” an invaderThe adaptive immune response counters specific invadersInfection or vaccination triggers active immunity.Vaccination (or immunization) exposes the immune system to a vaccine–a harmless variant of a microbe or–a part of a microbe.We can temporarily acquire passive immunity by receiving premade antibodies.On May 8, 1980 smallpox virus was declared eradicated!- virus is stored only in a few national health laboratoriesVaccination - Smallpox15 million infectionsLymphocytes mount a dual defenseLymphocytes–are responsible for adaptive immunity–originate from stem cells in the bone marrow–B lymphocytes or B cells continue developing in bone marrow–T lymphocytes or T cells develop further in the thymusLymphocytes mount a dual defenseB cells–participate in the humoral immune response–secrete antibodies into the blood and lymph.T cells–participate in the cell-mediated immune response1. attack cells infected with microbes2. stimulate B cells to produce antibodies.Figure 24.5ABonemarrowStem cellImmature lymphocytesViabloodAntigenreceptorsThymusT cellB cellViabloodFinal maturationof B and T cells in alymphatic organLymphnodes,spleen, andotherlymphaticorgansHumoralimmune responseCell-mediatedimmune responseTwo differentantibodymoleculesAntigen-bindingsiteAntigenmoleculeAntigenicdeterminantAntigen-binding site and antigenic determinant have complementary shapes (“lock and key”)Lymphocytes mount a dual defenseMillions of kinds of B cells and T cells–each with different antigen receptors, capable of binding one specific type of antigen–only a few B and T cells may recognize a new antigenClonal selection musters defensive forces against specific antigensWhen an antigen enters the body, it binds to only a few B and T cells in the lymphatic systembinding with the antigen activates these lymphocytesactivation initiates clonal selectionIn clonal selection, the selected lymphocyte cells–multiply into clones of short-lived effector cells, specialized for defending against the antigenAND–multiply into memory cells, which confer long-term immunityClonal selection musters defensive forces against specific antigensThe clonal selection of B cells occurs in two phases.–In the primary immune response, clonal selection produces –effector (plasma) cells and–memory cells that may confer lifelong immunity.–In the secondary immune response, memory cells are activated


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