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1、Lecture 6微生物学美国IndianaUniversityPurdueUniversity授课06 Still waters run deep.流静水深流静水深,人静心深人静心深 Where there is life,there is hope。有生命必有希望。有生命必有希望Lecture 6Leukocyte ChemotaxinsTypes of chemotaxinsC5a attracts neutrophils and monocytesMade by bacteriaPeptide clipped off N-terminus(beginning with N-formyl
2、methionine)during peptide maturation after protein synthesisMade by bacteria and nucleated blood cellsLeucotrieneslipid products of cell membrane metabolismBIOL 5332Lecture 6Leukocyte ChemotaxinsFunction of chemotaxinsEnhance and direct motility of phagocytic cellsTo a limited extent,oxidative metab
3、olism of phagocytic cellsBIOL 5333Lecture 6Opsonization and OpsoninsGeneral aspectsSubstances that enhance ability of phagocytes to ingest microbesDefend against presence of capsules and other microbial mechanisms that interfere with phagocytosisBIOL 5334Lecture 6Opsonization and OpsoninsTypes of op
4、soninsAntibodiesC3b component of complementBinds covalently to bacterial surface and is recognized by receptors on neutrophils,monocytes,and macrophageBacteria become bound to surface of phagocyte facilitating their uptakeBIOL 5335Lecture 6Opsonization and OpsoninsTypes of opsonins,continuedMechanis
5、mWhite blood cell receptors for C3bAt least 3CR1,CR2,CR3(complement receptor)Children deficient in CR3 very vulnerable to bacterial infectionsBIOL 5336Lecture 6PhagocytesTypes of CellsNeutrophilscell originActively motile cells produced in bone marrowDifferentiate from stem cells over about a two-we
6、ek periodProduction of granules during this timeAzurophilProduce specific granules laterBIOL 5337Lecture 6PhagocytesTypes of CellsNeutrophilscell origin,continuedUpon maturation(in numbers of 1010 per day),they move into peripheral blood and circulate for about 6.5 hoursNext move into capillary bed
7、and marginateBIOL 5338Lecture 6PhagocytesTypes of CellsNeutrophilscell origin,continuedMargination caused by stickiness due to interleukin-1Summoned by chemotaxis,they move through endothelial cell junctions(diapdesis)into extravascular tissue spacesBIOL 5339Lecture 6PhagocytesTypes of CellsNeutroph
8、ils are most active in gutGut has enormous microbial population lying just one cell layer away from aseptic tissueFlora generates large amounts of chemotaxins that recruit most of bodys available leukocytesBIOL 53310Lecture 6PhagocytesTypes of CellsAs a result,submucosa of gut is in a constant state
9、 of inflammationKeep microbial flora downSynthesis of neutrophils inhibited by chemicals or radiationInfections in gut regionBIOL 53311Lecture 6PhagocytesTypes of CellsMonocytes and macrophageCompared to neutrophilsArrive at damaged tissue later in infectionDays after neutrophils have been active in
10、 fighting intrudersEventually settle in tissues and become resident macrophageBIOL 53312Lecture 6PhagocytesTypes of CellsMonocytes and macrophageShare progenitor cell type,but kinetics of maturation&appearance are very differentMonocytes continue cell differentiation after leaving bone marrowMonocyt
11、es and macrophage involved in both constititive and inducible mechanismsInteract with T cells and play important role in cell-mediated immunityBIOL 53313Lecture 6PhagocytesTypes of CellsTissue(resident)macrophageExist throughout bodyDifferent names and functions in different tissuesKupffer cellslive
12、rAlveolar macrophagelungsOsteoclastsboneMicrogliabrainBIOL 53314Lecture 6PhagocytesTypes of CellsMonocyte and macrophage functionsPhagocytize invading microbesContribute greatly to inflammatory responseReleasesIL-1enhances sticking of neutrophil to capillary endotheliaTNFactivates newly arrived neut
13、rophilsBIOL 53315Lecture 6Mechanism of Phagocyte KillingNeutrophilsGeneral stepsAttach to microbesIngest microbesKill microbesGranulesconsidered as enlarged lysosomes containing hydrolytic enzymesBIOL 53316Lecture 6Mechanism of Phagocyte KillingNeutrophil granule typesAzurophil(primary granule)Conta
14、insLysozymeElastaseA chymotryptic-like proteaseMyeloperoxidaseSeveral antibacterial cationic proteinsBIOL 53317Lecture 6Mechanism of Phagocyte KillingNeutrophil granule typesSpecific(secondary granule)ContainsCytochromeLysozymeLactoferin(iron-binding protein)Vitamin B12 binding proteinCollagenaseBIO
15、L 53318Lecture 6Mechanism of Phagocyte KillingThe neutrophil membraneContains receptors for chemotaxin and opsoninsAfter binding chemotaxins,receptors are internalized and replaced with new onesBIOL 53319Lecture 6Mechanism of Phagocyte KillingEffectiveness of chemotaxis:very effectiveNeutrophils are
16、 very motileMove by rearranging cytoplasmic microfilaments and microtubulesActin and myosin in microfilaments are affected by protein gelsolinPortions that face upstream in chemotactic gradient form structure called lamellipodiumCytoplasm is densely packed with microfilamentsPortions face downstream
17、 form knob-like uropodBIOL 53320Lecture 6Mechanism of Phagocyte KillingProcess of phagocytosisGeneral aspectsDiffers from pinocytosis in that particles,not liquids,taken upBIOL 53321Lecture 6Mechanism of Phagocyte KillingProcess of phagocytosis,continuedReceptors on phagocyte surface progressively a
18、ttach to ligands on bacterial surfaceStimulates mechanisms of killingOxidative metabolism leading to production of hydrogen peroxide and compounds lethal to microbes(oxygen-dependent killing)Discharge of toxic compounds from granules into phagosome(oxygen-independent killing)BIOL 53322Lecture 6Mecha
19、nism of Phagocyte KillingProcess of phagocytosis,continuedForm phagosomepouch-like structure that invaginates,displacing the nucleus and granules toward uropodForm phagolysosomemembrane of granules and phagosome fuse,releasing toxic substancesForms separate pinched-off organelleBacteria coated with
20、antibacterial proteinsBIOL 53323Lecture 6Oxygen-Dependent KillingFusion of specific granules with phagosome membrane(derived from plasma membrane)brings together:NADPH oxidase(oxidizes NADPH;found in neutrophil plasma membrane)Unique cyt b(granule membrane)A quinoneBIOL 53324Lecture 6Oxygen-Dependen
21、t KillingReactionO2 O2(reduces oxygen to superoxide radical)2O2 +H2O H2O2+O2(superoxide dismutase)BIOL 53325Lecture 6Oxygen-Dependent KillingPatients lacking cytochrome componentsChildren having chronic granulomatous disease(CGD)Failure to synthesize superoxide radical and therefore hydrogen peroxid
22、eDue to decreased amount of cytochrome bGene for larger subunit is missing(90K,20K)BIOL 53326Lecture 6Oxygen-Dependent KillingChildren having chronic CGD,contd.Neutrophils can phagocytize normally,but do not efficiently oxidize NADPH and kill via oxidative pathwayUsually dont survive into adulthoodB
23、IOL 53327Lecture 6Oxygen-Dependent KillingHow does oxidative process kill?Interaction with myeloperoxidase supplied by fusion with azurophilCombines chloride ions and hydrogen peroxide to form hypochlorous ions(analogous to bleach)Bacteria lacking catalase produce hydrogen peroxide(pneumococci);basi
24、cally commit suicidePneumococci are not dangerous to CGD patientsBIOL 53328Lecture 6Oxygen-Independent KillingProcessTriggered by binding opsonized bacteria to the plasma membrane of neutrophilsSpecific granules fuse firstDeliver several bacteriodical proteins,including lysozyme and lactoferinBIOL 5
25、3329Lecture 6Oxygen-Independent KillingAzurophil granules discharge antimicrobial cationic proteinsSome are amphipathic and resemble other cationic surface proteins such as polymyxin BBIOL 53330Lecture 6Oxygen-Independent KillingAzurophil granules,continuedDisrupt outer membrane of Gram and kill by
26、causing leakage of vital componentsEach of the proteins has unique antimicrobial spectrum,but tend to affect Gram more than Gram+Proteins may account for survival of some CGD childrenBIOL 53331Lecture 6Oxygen-Independent KillingEfficiencyBacterial killing under highly anaerobic conditions of deep ab
27、scessesPatients lacking genesCoding for cationic proteinsNone found,maybe lethalBIOL 53332Lecture 6Oxygen-Independent KillingChediak-Higashi syndrome(genetic disease)Premature fusion of neutrophil granules while cells in bone marrowWhen mature cells phagocytize,granules are already spent,substantial
28、ly reducing killing powerBIOL 53333Lecture 6Comparison of Bacterial SensitivityGram rods in gut killed by oxygen-independentGram+bacteria on skin and upper respiratory epithelia are resistant to oxygen-independent and killed by oxygen-dependentBIOL 53334Lecture 6Mechanism of Phagocyte KillingEosinop
29、hilsMuch like neutrophils,but indicative of parasitic infectionBIOL 53335Lecture 6Killing by Monocytes and MacrophageGeneral aspectsTend to take care of what is left after battle with neutrophilsMechanisms of chemotaxis,phagocytosis,and killing resemble mechanisms of neutrophilsNot studied in same d
30、etailBIOL 53336Lecture 6Killing by Monocytes and MacrophageDifferencesContinue to differentiate after leaving bone marrow and are activatedCalled“angry macrophage”Phagocytize more vigorouslyTake up more oxygenSecrete large quantity of hydrolytic enzymesIn general,better prepared to killBIOL 53337Lec
31、ture 6Killing by Monocytes and MacrophageActivated byElicited by substances made in response to presence of bacteria(C3b)or viruses(interferon)Endotoxin of GramTetrapeptide derived from immunoglobulins(tuftsin)BIOL 53338Lecture 6Killing by Monocytes and MacrophageMicrobial(bacterial,fungi,protozoa)g
32、rowth withinSome can grow until activated,then killedParticipation in immune responseHelp rid body of not only microbial invaders,but also tumor and foreign cellsBIOL 53339Lecture 6Killing by Monocytes and MacrophageImmune response processStimulate development of T lymphocytesRespond to signals from
33、 other lymphocytes that stimulate differentiation and activation of macrophageBIOL 53340Lecture 6Phagocytotic KillingMacrophages/neutrophils/mast cells stimulated byTNFinterferonProduce reactive nitrogen intermediatesNitric oxideNitrite(NO2)Nitrate(NO3)BIOL 53341Lecture 6Phagocytotic KillingReleased
34、 from cells or contained within vacuolesMacrophages produce NO from arginine when stimulated by cytokinesNO can block cellular respiration by complexing iron in electron transport proteinsBIOL 53342Lecture 6Macrophage KillingHerpes simplexToxoplasma gondiiLeishmania majorCryptococcus neoformansSchistosoma mansoniBIOL 53343Lecture 6Lecture 6Questions?Comments?Assignments.BIOL 53344