Book 2Unit 7Text B.docx

Book 2Unit 7Text B.docx

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Book2Unit7TextB

UnitSevenNewResearchesintheFieldofImmunology

TextB

CanWeSelectivelyShutOffImmuneResponses?

1Inthepastfewdecades,organtransplantationhasgonefromexperimentaltoroutine.IntheUnitedStatesalone,morethan20,000heart,liver,andkidneytransplantsareperformedeveryyear.Butfortransplantrecipients,oneprospecthasremainedunchanged:

alifetimeoftakingpowerfuldrugstosuppresstheimmunesystem,atreatmentthatcanhaveserioussideeffects.Researchershavelongsoughtwaystoinducetheimmunesystemtotolerateatransplantwithoutbluntingthebody'sentiredefenses,butsofar,theyhavehadlimitedsuccess.

2Theyfaceformidablechallenges.Althoughimmunetolerancecanoccur—inrarecases,transplantrecipientswhostoptakingimmunosuppressantshavenotrejectedtheirforeignorgans—researchersdon'thaveaclearpictureofwhatishappeningatthemolecularandcellularlevelstoallowthistohappen.Tinkeringwiththeimmunesystemisalsoabitliketinkeringwithamechanicalwatch:

Fiddlewithonepart,andyoumaydisruptthewholemechanism.Andthereisabigroadblocktotestingdrugsdesignedtoinducetolerance:

Itishardtoknowiftheyworkunlessimmunosuppressantdrugsarewithdrawn,andthatwouldriskrejectionofthetransplant.Butifresearcherscanfigureouthowtotraintheimmunesystemtotoleratetransplants,theknowledgecouldhaveimplicationsforthetreatmentofautoimmunediseases,whichalsoresultfromunwantedimmuneattack—inthesecasesonsomeofthebody'sowntissues.

3AreportinScience60yearsagofiredthestartinggunintheracetoinducetransplanttolerance—aracethathasturnedintoamarathon.RayOwenoftheUniversityofWisconsin,Madison,reportedthatfraternaltwincattlesometimesshareaplacentaandarebornwitheachother'sredbloodcells,astatereferredtoasmixedchimerism.Thecattletoleratedtheforeigncellswithnoapparentproblems.

4Afewyearslater,PeterMedawarandhisteamattheUniversityofBirmingham,U.K.,showedthatfraternaltwincattlewithmixedchimerismreadilyacceptskingraftsfromeachother.MedawardidnotimmediatelyappreciatethelinktoOwen'swork,butwhenhesawtheconnection,hedecidedtoinjectfetalmiceinuterowithtissuefrommiceofadifferentstrain.InapublicationinNaturein1953,theresearchersshowedthat,afterbirth,someofthesemicetoleratedskingraftsfromdifferentstrains.Thisinfluentialexperimentledmanytodevotetheircareerstotransplantationandalsoraisedhopesthattheworkwouldleadtocuresforautoimmunediseases.

5Immunologists,manyofthemworkingwithmice,havesincespelledoutseveraldetailedmechanismsbehindtolerance.Theimmunesystemcan,forexample,dispatch“regulatory”cellsthatsuppressimmuneattacksagainstself.Orthesystemcanforceharmfulimmunecellstocommitsuicideortogointoadysfunctionalstuporcalledanergy.Researchersindeednowknowfinedetailsaboutthegenes,receptors,andcell-to-cellcommunicationsthatdrivetheseprocesses.

6Yetit’sonemattertounravelhowtheimmunesystemworksandanothertofigureoutsafewaystomanipulateit.Transplantresearchersarepursuingthreemainstrategiestoinducetolerance.OnebuildsonMedawar'sexperimentsbytryingtoexploitchimerism.Researchersinfusethepatientwiththeorgandonor'sbonemarrowinhopesthatthedonor’simmunecellswillteachthehosttotoleratethetransplant;donorimmunecellsthatcomealongwiththetransplantedorganalso,somecontend,canteachtolerance.AsecondstrategyusesdrugstotrainTcellstobecomeanergicorcommitsuicidewhentheyseetheforeignantigensonthetransplantedtissue.ThethirdapproachturnsupproductionofTregulatorycells,whichpreventspecificimmunecellsfromcopyingthemselvesandcanalsosuppressrejectionbysecretingbiochemicalscalledcytokinesthatdirecttheimmuneorchestratochangeitstune.

7Allthesestrategiesfaceacommonproblem:

Itismaddeninglydifficulttojudgewhethertheapproachhasfailedorsucceededbecausetherearenoreliable“biomarkers”thatindicatewhetherapersonhasbecometoleranttoatransplant.Sotheonlywaytoassesstoleranceistostopdrugtreatment,whichputsthepatientatriskofrejectingtheorgan.Similarly,ethicalconcernsoftenrequireresearcherstotestdrugsaimedatinducingtoleranceinconcertwithimmunosuppressivetherapy.This,inturn,canunderminethedrugs'effectivenessbecausetheyneedafullyfunctioningimmunesystemtodotheirjob.

8Ifresearcherscancompletetheir50-yearquesttoinduceimmunetolerancesafelyandselectively,theprospectsforhundredsofthousandsoftransplantrecipientswouldbegreatlyimproved,andso,too,mighttheprospectsforcontrollingautoimmunediseases.

Source:

Science1July2005:

Vol.309no.5731p.97

DOI:

10.1126/science.309.5731.97ByJonCohen

http:

//www.sciencemag.org/content/309/5731/97.full

（words:

760）

WordsandExpressions

recipient[rɪ'sɪpɪənt]n.apersonwhogetssomething接受者

immunosuppressant[,ɪmjʊnəʊsə'presənt]n.adrugthatlowersthebody'snormalimmuneresponse[免疫][药]免疫抑制剂（素）

reject[rɪ'dʒekt]vt.refusetoacceptoracknowledge拒绝；排斥；抵制；在免疫上排斥

tinker['tɪŋkə]vt.trytofixormend修补；粗修

fraternal[frə'tɜːnl]adj.derivedfromtwoova由两个受精卵发育而成的（孪生子）；异卵双生的[区别于identical]

fraternaltwin异卵双生

placenta[plə'sentə]n.thevascularorganinmammalsexceptmonotremesandmarsupialsthatunitesthefetustothematernaluterusandmediatesitsmetabolicexchangesthroughamoreorlessintimateassociationofuterinemucosalwithchorionicandusuallyallantoictissues;also:

ananalogousorganinanotheranimal[胚]胎盘；[植]胎座

graft[grɑ:

ft]vi./vt.toimplant（livingtissue）surgically移植；嫁接

n.移植；嫁接

fetal['fiːtl]adj.oforrelatingtoafetus【胚胎学】胎的；（似）胎儿的[亦作foetal]

inutero[ɪn'ju:

tərəʊ]intheuterus[拉丁语]在子宫内；尚未出生，在出生前

strain[streɪn]n.agroupofpresumedcommonancestrywithclear-cutphysiologicalbutusuallynotmorphologicaldistinctions种；族；菌株

dysfunctional[dɪs'fʌŋkʃənəl]adj.impairedorabnormalfunctioning（器官）功能紊乱的，机能不良（或失调）的，机能障碍的

stupor['stjuːpə]n.thefeelingofdistressanddisbeliefthatyouhavewhensomethingbadhappensaccidentally昏迷，恍惚；麻木

anergy['ænəʤɪ]n.aconditioninwhichthebodyfailstoreacttoanantigen【免疫学】无免疫性；抗原注射无反应性

anergic[æ'nɜ:

ʤɪk]adj.无免疫性的

biochemical[baɪəʊ'kemɪkəl]adj.oforrelatingtobiochemistry;involvingchemicalprocessesinlivingorganisms生物化学的

biochemicalreaction生物化学反应，生化反应

biochemicalengineering生化工程

biochemicalanalysis生化分析；生物技术分析；生物化学分析

biochemicaldegradation生物化学降解

cytokine['saɪtə,kaɪn]n.anyofaclassofimmunoregulatoryproteins（asinterleukinorinterferon）thataresecretedbycellsespeciallyoftheimmunesystem[细胞]细胞因子；细胞激素

biomarker[,baɪə'mɑ:

kə]n.生物标志物；生物标记；生物指标

immunosuppressive[,ɪmjʊnəʊsə'presɪv]adj.oforrelatingtoasubstancethatlowersthebody'snormalimmuneresponseandinducesimmunosuppression免抑制疫力的；抑制免疫力的

ComprehensionExercises

Exercise1Terminologyinterpretation

Directions:

Pleaseexplainthefollowingtermsbasedonyourunderstandingofthetext.

1）immunetolerance

2）mixedchimerism

3）functionsofTregulatorycells

4）biomarkers

Keys:

1）Immunetoleranceisasituationwhentransplantrecipientswhostoptakingimmunosuppressantshavenotrejectedtheirforeignorgans.

2）Mixedchemerismisastatewhenfraternaltwinsshareaplacentaandarebornwitheachother’sreadbloodcells.

3）ThefunctionofTregulatorycellsistopreventspecificimmunecellsfromcopyingthemselvesandsuppressrejectionbysecretingbiochemicalscalledcytokinesthatdirecttheimmuneorchestratochangeitstune.

4）Biomarkersarebiologicalmoleculesthatindicatewhetherapersonhasbecometoleranttoatransplantornot.

Exercise2Multiplechoices

Directions:

Pleasechoosethemostsuitablechoicetoeachquestionsbelow.

1）Whatisthebiggestproblemtransplantrecipientsencounter?

A）Therearescarcesourcesofthetransplantorgans.

B）Thetransplanttechnologyisstillatexperimentallevel.

C）Theirimmunesystemrejectstheforeignorgans.

D）Theimmunosuppressantshaveserioussideeffects.

2）Whatistheobstaclethattransplantresearchersareconfrontedwith?

A）Toseekformethodstoinduceimmunetolerancetotransplants.

B）Howtotrainimmunesystemtorejectforeignorgans.

C）Tofindoutthetreatmentsforautoimmunedisease.

D）Todecidewhetherdrugstestedforimmunetoleranceareeffectiveornot.

3）Whatistheimplicationoftheword“marathon”inParagraph3?

A）Seekingmethodstoinduceimmunetoleranceisalongwaytogo.

B）Theresearchworkneedsthespiritofpersistency.

C）Thescientists’devotioncanguaranteethesuccessoftheresearchworks.

D）Alloftheabove.

4）Whichimmunemechanismisnotexplainedbytheimmunologists?

A）Thesafewaytoapplyimmunesystemtoinducetolerancetoforeignorgans.

B）Theimmunesystemcanforceharmfulimmunecellstocommitsuicide.

C）Cell-to-cellcommunicationscandrivetheharmfulimmunecellsintoanergicsituation.

D）Regulatorycellscanbesenttosuppressimmuneattacksagainstself.

5）Whatdosereliable“biomarker”refertoaccordingtothetext?

A）Tcellstrainedtotoleratethetransplant.

B）Anybiologicalmoleculesindicatingwhetherapersonhasbecometolerancetoatransplant.

C）Tregulatorycellsusedtoadaptforeignorganstoimmunesystem.

D）Cytokinespreventingspecificimmunecellsfromcopyingthemselves.

6）Whichofthefollowingstatementsisincorrectaccordingtothetext?

A）Researchershaveunderstoodtheprincipleofimmunetoleranceatthemolecularandcellul