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COMMENTOpenAccessFOXP3andGARP(LRRC32):themasteranditsminionMichaelProbst-Kepper1*,JanBuer2AbstractThetranscriptionfactorFOXP3isessentialforthedevelopmentandfunctionofCD4+CD25hiFOXP3+regulatoryT(Treg)cells,butalsoexpressedinactivatedhumanhelperTcellswithoutacquisitionofaregulatoryphenotype.
Thiscommentfocusesonglycoprotein-Arepetitionspredominant(GARPorLRRC32)recentlyidentifiedasspecificmar-kerofactivatedhumanTregcells,whichmayprovidethemissinglinktowardabettermoleculardefinitionoftheregulatoryphenotype.
Reviewers:DrJimDiDanto,DrBeneditaRochaandDrWernerSolbach.
IntroductionProposedroleofFOXP3inself-toleranceThemaintenanceofself-toleranceinvolvescentralandperipheralmechanisms,buttheprocessofthymicnega-tiveselectionisimperfect.
Self-reactingclonesthatescapecentraltolerancearekeptincheckbyavarietyofperipheraltolerancemechanisms,inwhichthedomi-nanttoleranceexertedbyCD4+CD25+regulatoryT(Treg)cellsplaysanimportantrole.
ThedevelopmentandfunctionofTregcellscruciallydependsonthefork-head/wingedhelixtranscriptionfactorFOXP3.
ThisdependenceiscompellinglyillustratedbythefactthatlossoffunctionofFOXP3leadstothedevelopmentofthefatalautoimmunelymphoproliferativedisorderIPEX(immunodysregulation,polyendocrinopathy,andentero-pathy,X-linked)syndrome[1,2].
Similarly,lossoffunc-tionofFoxP3inmice,eithernatural(scurfy)orrecombinant,resultsinananalogousimmunepathologyduetoalackofTregcells[3-5].
ThedominantroleofFOXP3isfurthercorroboratedbythefactthatthegainoffunctioninducedbyectopicexpressioninconven-tionalCD4+CD25-helperT(Th)cellsleadstotheacqui-sitionofsuppressorfunctionandtheinductionofapartialregulatoryphenotypeinmiceandhumans[3,6-8].
DespiteadvancesinourunderstandingofTreg-celllineagecommitmentandfunction,gainedmainlybythestudyofFoxP3knock-out/knock-inmice[4,5,9-11],thedominantroleofFOXP3inthehumansystemanditssuitabilityasabonafidemarkerofhumanTregcellshavebeenquestioned[8,12-14].
WhyshouldTregcellsneedmorethanFOXP3ThereasoningthatmorethanFOXP3isnecessaryforfullyexplainingtheregulatoryphenotypeinhumansissupportedbyseveralobservations.
First,T-cellreceptor(TCR)stimulationofCD4+CD25-FOXP3-TcellsleadstotheinductionofFOXP3withoutinterferingwiththeexpressionofeffectorcytokinessuchasinterleukin-2andinterferon-g[15-17].
Second,theexpressionofFOXP3byconventionalCD4+CD25-ThcellsandevenbyThlinesandclonesdoesnotnecessarilyindicatetheacquisitionofsuppressorfunction[8,12,17-19].
Third,andmorespecifically,ithasrecentlybeenfoundthatdemethylationofaconservedFOXP3intronicregionmaybeabettermarkerforsuppressorfunctionthanthedifferentialexpressionofFOXP3atthemRNAorpro-teinlevelinTregandThcellclones[20].
Fourth,ectopicexpressionofFOXP3inhumanThcellsdoesnotleadtotheestablishmentofastableregulatoryphenotype[8,12,21].
Finally,althoughtheenhancementofFOXP3expressionbytransforminggrowthfactor-b1(TGF-b1)inactivatedhumanCD4+CD25-Thcellsgeneratesso-calledinducedTreg(iTreg)cells,thisphenotypeisrapidlylost[19,21,22].
Altogether,theseobservationssuggestthatmorethanFOXP3isnecessaryforfullyexplainingtheregulatoryphenotype.
Aplausibleexplanationforthequalitativeandquanti-tativedifferencesintheexpressionofFOXP3inhumanThandTregcells,withtheirmutuallyexclusiveeffector*Correspondence:m.
probst-kepper@klinikum-braunschweig.
de1InstituteforMicrobiology,ImmunologyandHygiene,StdtischesKlinikumBraunschweiggGmbH,Braunschweig,GermanyProbst-KepperandBuerBiologyDirect2010,5:8http://www.
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com/content/5/1/82010Probst-KepperandBuer;licenseeBioMedCentralLtd.
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0),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
andregulatoryfunctions,isthepresenceofaTreg-speci-fichigher-orderregulatorynetwork[13,14,23].
Thepos-sibilitythatTreg-specificcontrolmechanismscanmaintainsustainedhighlevelsofFOXP3andcancon-troltheregulatoryfunctionhasbeenaddressedonlyrecentlywiththeidentificationoftheglycoprotein-Arepetitionspredominant(GARPorLRRC32)receptor[21,24-28].
IdentificationandcharacterizationofGARPasasafeguardofFOXP3GARPwasidentifiedbasedontheanalysisofgeneexpressionprofilingofTregandThcellsfollowingTCRstimulation,sinceTCRstimulationdoesleadtotheinductionoftheirmutuallyexclusivefunctions[21,24].
GARPisspecificallyinducedinCD4+CD25hiFOXP3hiTregcellsandthusisaTreg-specificactivationmarker[21,24-27].
BecausetheexpressionofGARPisup-regu-latedinFOXP3-transducedThcells,GARPobviouslydependsonFOXP3,andthisfindingsuggestsapotentialcontributiontotheregulatoryphenotype[21,29].
ThefunctionofGARPhasbeenelucidatedbyectopicover-expressioninhumanalloantigen-specificThcellsanddown-regulationofGARPinhumanantigen-speci-ficTregcells[21,29].
Retroviralover-expressionofGARPinThcells,aftersomeroundsofTCRstimulation,leadstoanefficientandstablereprogramming/transdifferen-tiationoftheestablishedeffectortowardtheregulatoryprogram.
ThisfindingisassociatedwithconstitutiveexpressionofFOXP3,theb-galactosidebindingproteinlectin,galactoside-binding,soluble,3(LGALS3)[8,30],andthecysteine-endoproteaselegumain(LGMN)[8]andwithanextendedTreg-signaturewithsuppressionofeffectorcytokineproductionandacquisitionofregula-toryfunctionssimilartothoseofTregcells[21,29].
Thus,aFOXP3-regulatinggenehasbeenidentifiedinthehumansystem,andthisfindingsuggeststhattheGARPsignalingpathwaymayhavedirecttherapeuticapplications[28,31]similartothosethathavebeendescribedforCD83inthemurinesystem[32].
Incontrast,lentiviraldown-regulationofGARPinhumanalloantigen-specificTregcellsbyspecificsmallinterferingRNA(siRNA)substantiallyimpairssuppres-sorfunctionandFOXP3expressionthatisassociatedwithimpairedinductionofCD83andCD27,bothknowntoregulateFOXP3[21,32,33].
Morestrikingisthefactthatsimilarchangesareinducedbythedown-regulationofFOXP3inTregcells,afindingthatpro-videscompellingevidenceforaGARP-FOXP3positivefeedbackloopinTregcells.
BecausethisfeedbackloopseemstobeinterrelatedwithotherFOXP3-regulatingsystemssuchasCD83andCD27,theexistenceofahigher-orderregulatorynetworkasdiscussedrecentlybyHori[13],canbespeculated(Figure1a).
Thus,GARPisaspecificmarkerofactivatedTregcellsandcanexplainthequalitativeandquantitativediffer-encesinFOXP3expressionandfunctioninTregcellsandThcells.
LackofGARPexpressionfurtherdiffer-entiatesandexplainsthetransientnatureofTGF-b-inducediTregcells[19],suggestingthatnaturalandiTregcellsmayrepresentalternativedifferentiationstagesofsuppressorcells[21,26].
Inlinewiththeseobservations,aspecificallyhypomethylatedregioninintron1ofGARPandtwodifferentiallymethylatedregionswithenhancerfunctionsinTregcellshaverecentlybeenchar-acterized.
Thesefindingshaveidentifiedanepigeneticbasisforthelineage-specificdifferenceinGARPexpres-sion[34].
GARPbringslatentTGF-bintoanewgameMembersoftheTGF-bfamilyarepleiotropiccytokineswithcrucialfunctionsindifferentiation,morphogenesis,andimmunehomeostasis.
TheirfunctioninimmunehomeostasisisevidencedbythefactthatdysregulationofTGF-bfunctionsisassociatedwithautoimmunity[35].
Likemanyothercelltypes,humanTregandThcellscansecretelatentTGF-b[20,36].
However,latency-associatedpeptide(LAP)preventstheactivationoflatentTGF-btowardtheactivematureTGF-b[37].
TheselectiveinductionofLAPandtheactivationofactiveTGF-buponTCRstimulationhasbeenreportedonlyforhumanTregcellsandclones[20,37,38].
ThisfindingfurtherexplainstheTGF-bspecifictranscrip-tionalsignatureanddetectionofexpressionofphos-phorylatedSMAD2inTregcellsofhumanandmurineorigin[20,23,37,39].
Moreover,specificup-regulationofLAPonactivatedhumanTregcellshasbeenshowntoallowimprovementsinthepurityofTregcellisolationproceduresbyseparatingactivatedLAP+FOXP3+TregcellsfromcontaminatingeffectorLAP-FOXP3+/loThcells[38].
Thus,besidesbeingamarkerofactivatedTregcellsincomplexwithLAP,TGF-b1isanimportantmodulatorofFOXP3expression[19,21,40],andapoten-tialmediatorofinfectioustolerancebyitsactionincon-vertingFoxP3-murineCD4+TcellsintofunctionalFoxP3+iTregcells[41].
Theissueofcell-surfacebindingofLAP/latentTGF-bonhumanTregcellshasbeenaddressedonlyrecentlywiththeidentificationofGARPasareceptorofthiscomplex[26,27].
Therefore,twoimportantregulatorycircuitsofTregcellscometogether:theGARP-FOXP3feedbackloopandtheautocrineTGF-bloop(Figure1b).
Withthat,thepotentialsynergyofmanyoftheTregsignaturecomponentsthatareessentialfortheregula-torypropertiesthathavebeenascribedtoTCRactiva-tion,interleukin-2,TGF-b,andFOXP3itself[20,23]couldbeexplainedbythisparticularspatiotemporalinterplayofinterrelatedsignalingsystemsonTregcells.
Probst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page2of6Figure1GARPassafeguardoftheregulatoryphenotype.
(A)Qualitative(lineage-specific)andquantitative(dose-effect)differencesinFOXP3expressioninhumanhelperTcells(Th;upperpanel)andregulatoryTcells(Treg;lowerpanel)areduetolineage-specificmethylationoftherespectiveloci(indicatedbyblackdots)andthustheexpressionofthegenesFOXP3andGARP.
InhumanTregcells,apositivefeedbackloophasbeenfoundbetweenGARPandFOXP3;thisfeedbackloopisinterrelatedwiththeFOXP3-enhancingmoleculesindicated.
PhosphorylationofLGALS3(indicatedbyaP)hasbeenreportedtobeessentialfortheFOXP3-regulatingfunction[21].
GARPisareceptorforLAP/latentTGF-b[26,27].
T-bet(T-boxexpressedinTcells),GATA3(GATA-bindingprotein3),RORg(retinoic-relatedorphanreceptorgamma)representtranscriptionfactorsofTh1,Th2,andTh17cells.
(B)ImplicationsforhumanandmurineTcells,respectively,oftheautocrineandparacrineeffectsofGARPandNrp1surface-boundLAP/latentTGF-bafteractivationofTGF-b.
TheTGF-bsignaturephospho-SMAD2(pSMAD2)hasbeenobservedinhuman(GARP+)andmurine(Nrp1+)Tregcells.
Paracrineeffectsincludethegenerationofinfectioustolerance.
(C)StructuralcompositionoftheLAP/latentTGF-bbindingproteinsNrp1andGARP(LRR,leucine-richrepeatdomain;CUB,complementsubcomponentsC1r/C1sdomain;F5/8coagulationfactordomain;MAM,meprin,A5,andreceptorprotein-tyrosinphosphataseμdomain;TM,transmembraneregion;L,leaderpeptide).
NIP(Nrp1interactingprotein)isaNrp1bindingproteininvolvedintheregulationofNrp1-mediatedsignalingasamolecularadapter[48].
Probst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page3of6Perspective:doesNrp1representafunctionalhomologueofGARPinmurineTregcellsTheidentificationofGARPasareceptorforLAP/latentTGF-bopensspeculationaboutapotentialcommondenominator.
Thereasonforsuchspeculationisthatneuropilin1(Nrp1),whichhasbeencharacterizedasamarkerofCD4+CD25+TregcellsinmicethatenhancesTregcell/dendriticcellcontactduringantigenrecogni-tion[42,43],hasalsobeencharacterizedasareceptorforLAP/latentTGF-b[39].
Moreover,murinesortedNrp1-TcellscapturesolubleNrp1(appliedasacon-stantfragment[Fc]-fusionprotein),andthecapturedNrp1increasestheirabilitytobindLAP/TGF-b1.
SuchcoatedTcellsacquirestrongregulatoryactivity[39].
Thus,Nrp1isaTGF-b1receptorthat,unlikeGARP[27],alsoactivatesthelatentformofTGF-b1.
ThestructuraldifferencesbetweenGARP,aToll-likereceptorhomologuewithleucine-richrepeats,andthemulti-domainproteinNrp1,areceptorforclass-3sema-phorin-familyproteinsandvascularendothelialgrowthfactor(Figure1c)[44],necessitatefurtherbiochemicalandmolecularanalysestoidentifyspecificbindinginter-actionsandpotentiallyassociatedmolecules.
TheissueofGARPexpressioninmurineTregcellsattheproteinlevelremainstobeelucidated.
DiscussionsOpenQuestionsConcerningtheFunctionofGARPBecauseGARPisconstitutivelyexpressedonplatelets[26,45],andbecauseapotentialfunctionofGARPonthrombusformationhasrecentlybeenreported[46],importantquestionsaboutGARPsignalingandparallelfunctioninplateletscomparedtoTregcellscouldbeconsidered.
ConcerningthedependenceofGARPexpressiononFOXP3asdescribedabove,ithasbeenreportedthatFOXP3isexpressedbyhumanandmurinemegakaryocytes[47].
Therefore,thethrombocytopeniaandplateletabnormalitiesexperiencedbysomepatientswithIPEXsyndromecanbeexplainedbylossoffunc-tionofFOXP3[47];however,thisexplanationwouldsuggestaconcomitantimpairmentofGARPexpressionandfunctiononIPEXplatelets,animpairmentthathasnotyetbeenshown.
Acontroversialissueisthepotentialsuppressorfunc-tionofGARP,suggestedrecently[24],becauseplateletsasanaturalsourceofGARP-expressingcellsdonotfunctionassuppressorcells[21].
Therefore,differencesinthefunctionofGARPinplateletsandTregcellscanbesuggested.
ThisquestionisimportantforthepotentialdesignofGARP-selectivedrugsthatcanspecificallytar-getonlyTregcellsandnotplateletfunctions.
Asofnow,neithertheligandnorthesignalingsystemorpotentialco-receptor(s)ofGARPhasbeenidentified,andidentify-ingthemisthemostimportantchallengeforthefuture.
ConclusionsTheidentificationofGARPasalineage-specifickeyreceptorofhumanactivatedTregcells,whichisinpartcontrolledbylineage-specifichypomethylationoftheGARPlocus,thecharacterizationofaGARP-FOXP3positivefeedbackloopthatsafeguardsFOXP3expres-sioninTregcells,andthebindingofLAP/latentTGF-btoGARPprovideaconceptualframeworkforanewmoleculardefinitionoftheregulatoryprogram.
IfGARPisareceptorforthewell-knownimmunemodulatorTGF-bonhumanTregcells,andifNrp1playsthissameroleonmurineTregcells,thenthissimilaritymightexplainthesimilaritiesintheTGF-bsignaturesthathavebeenobservedinTregcellsinbothspecies.
ThesurfacebindingandactivationofTGF-bhaveobviousimplicationsforinfectioustolerance.
Completeelucida-tionoftheGARP/GARP-ligandsignalingsysteminTregcellsandplateletsisanimportantchallengeandaprere-quisiteforthefuturedevelopmentofstrategiesandtoolsforinducingorinhibitingTregcellsinchronicinfection,tumorimmunotherapy,autoimmunediseases,andtransplantation.
ListofabbreviationsusedGARP:glycoprotein-Arepetitionspredominant;IPEX:immunedysregulation,polyendocrinopathy,enteropathy,X-linked;iTregcells:inducedregulatoryTcells;LAP:latency-associatedpeptide;Nrp1:neuropilin1;SMAD:Sma-andMad-relatedprotein2;TCR:T-cellreceptor;TGF-b:transforminggrowthfactor-b;Thcells:helperTcells;Tregcells:regulatoryTcells.
Reviewers'commentsReviewer'sreport1Reviewer1:Dr.
JimDiSanto,CytokinesandLymphoidDevelopmentLab,InstitutPasteur,Paris,FranceReviewer'scomment:IhavereadyourcommentforBiologyDirectentitled"FOXP3andGARP(LRRC32):themasteranditsminion".
IfindthiscommenttobeinterestingandsuitableforpublicationinBiologyDirect.
Idonothaveanyspecificcommentsforwebpublication.
Reviewer'sreport2Reviewer2:Dr.
BeneditaRocha,InstitutNationaldelaSantéetdelaRechercheMédicale(INSERM)U591,Insi-tutNecker,FranceReviewer'scomment:Regulatorycellshaveafunda-mentalroleinmanydiseaseprocesses,andextensiveexperimentalandclinicaldataindicatethattoolspre-ventingorincreasingregulatoryfunctionwillhaveafundamentaltherapeuticrole.
WhileFOXP3expressiongenerallycorrelateswithregulationinthemouse,thisisnotsoinhumanTcells.
ThiscommentreviewsaProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page4of6fundamentalaspect,thefactorsbesidesFOXP3expres-sionthatensuretheinductionofastableregulatoryfunctiononhumancells,theircorrelationwithFOXP3regulationandtheirpossiblemechanismsofaction.
Ifoundthetopicactualandimportant,thecommentclearandcomprehensiveandstronglysupportpublication.
Reviewer'sreport3Reviewer3:Dr.
WernerSolbach,InsituteforMedicalMicrobiologyandHygiene,UniversityLübeck,GermanyReviewer'scomment:Thems.
dealswiththeconnec-tivityofFOXP3and"glycoprotein-Arepititionspredo-minantreceptor(GARPorLRRC32)inthecontextofthefunctioningofregulatoryTcells(Tregs).
ThistopicisofgreatrelevanceinthecontextofclarifyingtheequivocalroleofFOXP3anditspartnersforexplanationofregulatoryTcellcircuits.
ItisclearthatnotonlyFOXP3orGARPalone,butalsolatentlyactivatedTGF-biscrucialforthesuppressiveactivityofTregcells.
TheauthorsnowverynicelybringtogethertheGARP-FOXP3regulatorycircuitwiththeautocrineTGF-bloopwhichhelpstoexplainmanyTregfeatures.
Intheirperspective,theyalsotrytoopenthoughtfulavenueshowtobringtogether(human)GARPwithitspossiblefunctionalhomologueinmice,neuropilin1.
Insum-mary,theypresentavaluableconceptualframeworkforunderstandingtheregulatoryprogramintheTcellreac-tivitysystemandbeyond.
Thems.
iswellwrittenandeasytounderstand.
IrecommendpublicationinBiologyDirect.
AcknowledgementsMichaelProbst-KepperwassupportedbygrantsfromtheVolkswagenStiftung(I/73234)andtheDeutscheForschungsgemeinschaft(PR554/2).
Authordetails1InstituteforMicrobiology,ImmunologyandHygiene,StdtischesKlinikumBraunschweiggGmbH,Braunschweig,Germany.
2InstituteforMedicalMicrobiology,UniversityHospitalEssen,Essen,Germany.
Authors'contributionsMPKandJBbothwereinvolvedindraftingofthemanuscriptandapprovedthefinalversiontobepublished.
CompetinginterestsTheauthorsdeclarethattheyhavenocompetinginterests.
Received:27January2010Accepted:5February2010Published:5February2010References1.
ZieglerSF:FOXP3:OfMiceandMen.
AnnuRevImmunol2006,24:209-226.
2.
GambineriE,TorgersonTR,OchsHD:Immunedysregulation,polyendocrinopathy,enteropathy,andX-linkedinheritance(IPEX),asyndromeofsystemicautoimmunitycausedbymutationsofFOXP3,acriticalregulatorofT-cellhomeostasis.
CurrOpinRheumatol2003,15:430-435.
3.
KhattriR,CoxT,YasaykoSA,RamsdellF:AnessentialroleforScurfininCD4+CD25+Tregulatorycells.
NatImmunol2003,4:337-342.
4.
FontenotJD,RasmussenJP,WilliamsLM,DooleyJL,FarrAG,RudenskyAY:RegulatoryTcelllineagespecificationbytheforkheadtranscriptionfactorfoxp3.
Immunity2005,22:329-341.
5.
LinW,HaribhaiD,RellandL,TruongN,CarlsonM,WilliamsC,ChatilaT:RegulatoryTcelldevelopmentintheabsenceoffunctionalFoxp3.
NatImmunol2007,8:359-368.
6.
HoriS,NomuraT,SakaguchiS:ControlofregulatoryTcelldevelopmentbythetranscriptionfactorFoxp3.
Science2003,299:1057-1061.
7.
FontenotJD,GavinMA,RudenskyAY:Foxp3programsthedevelopmentandfunctionofCD4+CD25+regulatoryTcells.
NatImmunol2003,4:330-336.
8.
OcklenburgF,Moharregh-KhiabaniD,GeffersR,JankeV,PfoertnerS,GarritsenH,GroebeL,KlempnauerJ,DittmarKE,WeissS,BuerJ,Probst-KepperM:UBD,adownstreamelementofFOXP3,allowstheidentificationofLGALS3,anewmarkerofhumanregulatoryTcells.
LabInvest2006,86:724-737.
9.
WanYY,FlavellRA:IdentifyingFoxp3-expressingsuppressorTcellswithabicistronicreporter.
PNAS2005,102:5126-5131.
10.
WilliamsLM,RudenskyAY:MaintenanceoftheFoxp3-dependentdevelopmentalprograminmatureregulatoryTcellsrequirescontinuedexpressionofFoxp3.
NatImmunol2007,8:277-284.
11.
WanYY,FlavellRA:RegulatoryT-cellfunctionsaresubvertedandconvertedowingtoattenuatedFoxp3expression.
Nature2007,445:766-770.
12.
AllanSE,PasseriniL,BacchettaR,CrellinN,DaiM,OrbanPC,ZieglerSF,RoncaroloMG,LevingsMK:Theroleof2FOXP3isoformsinthegenerationofhumanCD4Tregs.
JClinInvest2005,115:3276-3284.
13.
HoriS:RethinkingthemoleculardefinitionofregulatoryTcells.
EurJImmunol2008,38:928-930.
14.
RoncaroloMG,GregoriS:IsFOXP3abonafidemarkerforhumanregulatoryTcells.
EurJImmunol2008,38:925-927.
15.
GavinMA,TorgersonTR,HoustonE,deRoosP,HoWY,Stray-PedersenA,OcheltreeEL,GreenbergPD,OchsHD,RudenskyAY:Single-cellanalysisofnormalandFOXP3-mutanthumanTcells:FOXP3expressionwithoutregulatoryTcelldevelopment.
ProcNatlAcadSciUSA2006,103:6659-6664.
16.
AllanSE,CromeSQ,CrellinNK,PasseriniL,SteinerTS,BacchettaR,RoncaroloMG,LevingsMK:Activation-inducedFOXP3inhumanTeffectorcellsdoesnotsuppressproliferationorcytokineproduction.
IntImmunol2007,19:345-354.
17.
FranoisV,OttavianiS,RenkvistN,StockisJ,SchulerG,ThielemansK,ColauD,MarchandM,BoonT,LucasS,BruggenvanderP:TheCD4+T-CellResponseofMelanomaPatientstoaMAGE-A3PeptideVaccineInvolvesPotentialRegulatoryTCells.
CancerRes2009,69:4335-4345.
18.
WangF,Ioan-FacsinayA,VoortvanderEIH,HuizingaTW,ToesRE:TransientexpressionofFOXP3inhumanactivatednonregulatoryCD4+Tcells.
EurJImmunol2007,37:129-138.
19.
TranDQ,RamseyH,ShevachEM:InductionofFOXP3expressioninnaivehumanCD4+FOXP3-TcellsbyTcellreceptorstimulationisTGF{beta}-dependentbutdoesnotconferaregulatoryphenotype.
Blood2007,110:2983-2990.
20.
StockisJ,FinkW,FrancoisV,ConnerotteT,deSmetC,KnoopsL,BruggenvanderP,CouliePG,LucasS:ComparisonofstablehumanTregandThclonesbytranscriptionalprofiling.
EurJImmunol2009,39:869-882.
21.
Probst-KepperM,GeffersR,KrgerA,ViegasN,ErckC,HechtHJ,LünsdorfH,RoubinR,Moharregh-KhiabaniD,WagnerK,OcklenburgF,JeronA,GarritsenH,ArstilaTP,KeklinenE,BallingR,HauserH,BuerJ,WeissS:GARP:akeyreceptorcontrollingFOXP3inhumanregulatoryTcells.
JournalofCellularandMolecularMedicine2010,13:3343-3357.
22.
TakakiH,IchiyamaK,KogaK,ChinenT,TakaesuG,SugiyamaY,KatoS,YoshimuraA,KobayashiT:STAT6InhibitsTGF-b1-mediatedFoxp3InductionthroughDirectBindingtotheFoxp3Promoter,WhichIsRevertedbyRetinoicAcidReceptor.
JBiolChem2008,283:14955-14962.
23.
HillJA,FeuererM,TashK,HaxhinastoS,PerezJ,MelamedR,MathisD,BenoistC:Foxp3Transcription-Factor-Dependentand-IndependentRegulationoftheRegulatoryTCellTranscriptionalSignature.
Immunity2007,27:786-800.
24.
WangR,WanQ,KozhayaL,FujiiH,UnutmazD:IdentificationofaRegulatoryTcellspecificCellSurfaceMoleculethatMediatesProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page5of6SuppressiveSignalsandInducesFoxp3Expression.
PLoSOne2008,3:e27705.
25.
WangR,KozhayaL,MercerF,KhaitanA,FujiiH,UnutmazD:ExpressionofGARPselectivelyidentifiesactivatedhumanFOXP3+regulatoryTcells.
PNAS2009,106:13439-13444.
26.
TranDQ,AnderssonJ,WangR,RamseyH,UnutmazD,ShevachEM:GARP(LRRC32)isessentialforthesurfaceexpressionoflatentTGF-bonplateletsandactivatedFOXP3+regulatoryTcells.
ProcNatlAcadSciUSA2009,106:13445-13450.
27.
StockisJ,ColauD,CouliePG,LucasS:MembraneproteinGARPisareceptorforlatentTGF-bonthesurfaceofactivatedhumanTreg.
EurJImmunol2009,39:3312-3322.
28.
Probst-KepperM,KrgerA,GarritsenHSP,BuerJ:PerspectivesonRegulatoryTCellTherapies.
TransfusMedHemother2009,36:302-308.
29.
Probst-KepperM,BallingR,BuerJ:FOXP3:RequiredbutNotSufficient.
TheRoleofGARP(LRRC32)asaSafeguardoftheRegulatoryPhenotype.
CurrMolMed2010.
30.
PfoertnerS,JeronA,Probst-KepperM,GuzmanCA,HansenW,WestendorfAM,ToepferT,SchraderAJ,FranzkeA,BuerJ,GeffersR:SignaturesofHumanRegulatoryTCells:AnEncounterwithOldFriendsandNewPlayers.
GenomeBiology2006,7:R54-1-R54-18.
31.
TranDQ,ShevachEM:TherapeuticpotentialofFOXP3regulatoryTcellsandtheirinteractionswithdendriticcells.
HumImmunol2009,70:294-299.
32.
ReinwaldS,WietheC,WestendorfAM,BreloerM,Probst-KepperM,FleischerB,SteinkassererA,BuerJ,HansenW:CD83ExpressioninCD4+TCellsModulatesInflammationandAutoimmunity.
JImmunol2008,180:5890-5897.
33.
YangZZ,NovakAJ,ZiesmerSC,WitzigTE,AnsellSM:CD70+non-HodgkinlymphomaBcellsinduceFoxp3expressionandregulatoryfunctioninintratumoralCD4+CD25Tcells.
Blood2008,110:2537-2544.
34.
SchmidlC,KlugM,BoeldTJ,AndreesenR,HoffmannP,EdingerM,RehliM:Lineage-specificDNAmethylationinTcellscorrelateswithhistonemethylationandenhanceractivity.
GenomeRes2009,19:1165-1174.
35.
WanYY,FlavellRA:TGF-betaandregulatoryTcellinimmunityandautoimmunity.
JClinImmunol2009,28:647-659.
36.
LevingsMK,SangregorioR,SartiranaC,MoschinAL,BattagliaM,OrbanPC,RoncaroloMG:HumanCD25+CD4+Tsuppressorcellclonesproducetransforminggrowthfactorbeta,butnotinterleukin10,andaredistinctfromtype1Tregulatorycells.
JExpMed2002,196:1335-1346.
37.
NakamuraK,KitaniA,FussI,PedersenA,HaradaN,NawataH,StroberW:TGF-beta1playsanimportantroleinthemechanismofCD4+CD25+regulatoryTcellactivityinbothhumansandmice.
JImmunol2004,172:834-842.
38.
TranDQ,AnderssonJ,HardwickD,BebrisL,IlleiGG,ShevachEM:Selectiveexpressionoflatency-associatedpeptide(LAP)andIL-1receptortypeI/II(CD121a/CD121b)onactivatedhumanFOXP3+regulatoryTcellsallowsfortheirpurificationfromexpansioncultures.
Blood2009,113:5125-5133.
39.
GlinkaJ,Prud'hommeGJ:Neuropilin-1isareceptorfortransforminggrowthfactor-1,activatesitslatentform,andpromotesregulatoryTcellactivity.
JLeukocBiol2008,84:302-310.
40.
FantiniMC,BeckerC,MonteleoneG,PalloneF,GallePR,NeurathMF:CuttingEdge:TGF-betaInducesaRegulatoryPhenotypeinCD4+CD25-TCellsthroughFoxp3InductionandDown-RegulationofSmad7.
JImmunol2004,172:5149-5153.
41.
AnderssonJ,TranDQ,PesuM,DavidsonTS,RamseyH,O'SheaJJ,ShevachEM:CD4FoxP3regulatoryTcellsconferinfectioustoleranceinaTGF-beta-dependentmanner.
JExpMed2008,205:1975-1981.
42.
BruderD,Probst-KepperM,WestendorfAM,GeffersR,BeissertS,LoserK,vonBoehmerH,BuerJ,HansenW:Frontline:Neuropilin-1:asurfacemarkerofregulatoryTcells.
EurJImmunol2004,34:623-630.
43.
SarrisM,AndersenKG,RandowF,MayrL,BetzAG:Neuropilin-1ExpressiononRegulatoryTCellsEnhancesTheirInteractionwithDendriticCellsduringAntigenRecognition.
Immunity2008,28:402-413.
44.
GerettiE,KlagsbrunM:Neuropilins:NovelTargetsforAnti-AngiogenesisTherapies.
CellAdhMigr2007,1:56-61.
45.
MacaulayIC,TijssenMR,Thijssen-TimmerDC,GusnantoA,StewardM,BurnsP,LangfordCF,EllisP,DudbridgeF,ZwagingaJJ,WatkinsNA,SchootvanderCE,OuwehandWH:Comparativegeneexpressionprofilingofinvitrodifferentiatedmegakaryocytesanderythroblastsidentifiesnovelactivatoryandinhibitoryplateletmembraneproteins.
Blood2007,109:3260-3269.
46.
O'ConnorN,SallesI,CvejicA,WatkinsNA,WalkerA,GarnerS,MacaulayIC,StewardM,ZwagingaJ,BrayS,DudbridgeF,deBonoB,GoodallAH,DeckmynH,StempleDL,OuwehandWH,BloodomicsConsortium:Functionalgenomicsinzebrafishpermitsrapidcharacterizationofnovelplateletmembraneproteins.
Blood2008,113:4754-4762.
47.
BernardJJ,SeweryniakKE,KoniskiAD,SpinelliSL,BlumbergN,FrancisCW,TaubmanMB,PalisJ,PhippsRP:Foxp3RegulatesMegakaryopoiesisandPlateletFunction.
ArteriosclerThrombVascBiol2009,29:1874-1882.
48.
CaiH,ReedRR:CloningandCharacterizationofNeuropilin-1-InteractingProtein:APSD-95/Dlg/ZO-1Domain-ContainingProteinThatInteractswiththeCytoplasmicDomainofNeuropilin-1.
JNeurosci1999,19:6519-6527.
doi:10.
1186/1745-6150-5-8Citethisarticleas:Probst-KepperandBuer:FOXP3andGARP(LRRC32):themasteranditsminion.
BiologyDirect20105:8.
SubmityournextmanuscripttoBioMedCentralandtakefulladvantageof:ConvenientonlinesubmissionThoroughpeerreviewNospaceconstraintsorcolorgurechargesImmediatepublicationonacceptanceInclusioninPubMed,CAS,ScopusandGoogleScholarResearchwhichisfreelyavailableforredistributionSubmityourmanuscriptatwww.
biomedcentral.
com/submitProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page6of6
Thiscommentfocusesonglycoprotein-Arepetitionspredominant(GARPorLRRC32)recentlyidentifiedasspecificmar-kerofactivatedhumanTregcells,whichmayprovidethemissinglinktowardabettermoleculardefinitionoftheregulatoryphenotype.
Reviewers:DrJimDiDanto,DrBeneditaRochaandDrWernerSolbach.
IntroductionProposedroleofFOXP3inself-toleranceThemaintenanceofself-toleranceinvolvescentralandperipheralmechanisms,buttheprocessofthymicnega-tiveselectionisimperfect.
Self-reactingclonesthatescapecentraltolerancearekeptincheckbyavarietyofperipheraltolerancemechanisms,inwhichthedomi-nanttoleranceexertedbyCD4+CD25+regulatoryT(Treg)cellsplaysanimportantrole.
ThedevelopmentandfunctionofTregcellscruciallydependsonthefork-head/wingedhelixtranscriptionfactorFOXP3.
ThisdependenceiscompellinglyillustratedbythefactthatlossoffunctionofFOXP3leadstothedevelopmentofthefatalautoimmunelymphoproliferativedisorderIPEX(immunodysregulation,polyendocrinopathy,andentero-pathy,X-linked)syndrome[1,2].
Similarly,lossoffunc-tionofFoxP3inmice,eithernatural(scurfy)orrecombinant,resultsinananalogousimmunepathologyduetoalackofTregcells[3-5].
ThedominantroleofFOXP3isfurthercorroboratedbythefactthatthegainoffunctioninducedbyectopicexpressioninconven-tionalCD4+CD25-helperT(Th)cellsleadstotheacqui-sitionofsuppressorfunctionandtheinductionofapartialregulatoryphenotypeinmiceandhumans[3,6-8].
DespiteadvancesinourunderstandingofTreg-celllineagecommitmentandfunction,gainedmainlybythestudyofFoxP3knock-out/knock-inmice[4,5,9-11],thedominantroleofFOXP3inthehumansystemanditssuitabilityasabonafidemarkerofhumanTregcellshavebeenquestioned[8,12-14].
WhyshouldTregcellsneedmorethanFOXP3ThereasoningthatmorethanFOXP3isnecessaryforfullyexplainingtheregulatoryphenotypeinhumansissupportedbyseveralobservations.
First,T-cellreceptor(TCR)stimulationofCD4+CD25-FOXP3-TcellsleadstotheinductionofFOXP3withoutinterferingwiththeexpressionofeffectorcytokinessuchasinterleukin-2andinterferon-g[15-17].
Second,theexpressionofFOXP3byconventionalCD4+CD25-ThcellsandevenbyThlinesandclonesdoesnotnecessarilyindicatetheacquisitionofsuppressorfunction[8,12,17-19].
Third,andmorespecifically,ithasrecentlybeenfoundthatdemethylationofaconservedFOXP3intronicregionmaybeabettermarkerforsuppressorfunctionthanthedifferentialexpressionofFOXP3atthemRNAorpro-teinlevelinTregandThcellclones[20].
Fourth,ectopicexpressionofFOXP3inhumanThcellsdoesnotleadtotheestablishmentofastableregulatoryphenotype[8,12,21].
Finally,althoughtheenhancementofFOXP3expressionbytransforminggrowthfactor-b1(TGF-b1)inactivatedhumanCD4+CD25-Thcellsgeneratesso-calledinducedTreg(iTreg)cells,thisphenotypeisrapidlylost[19,21,22].
Altogether,theseobservationssuggestthatmorethanFOXP3isnecessaryforfullyexplainingtheregulatoryphenotype.
Aplausibleexplanationforthequalitativeandquanti-tativedifferencesintheexpressionofFOXP3inhumanThandTregcells,withtheirmutuallyexclusiveeffector*Correspondence:m.
probst-kepper@klinikum-braunschweig.
de1InstituteforMicrobiology,ImmunologyandHygiene,StdtischesKlinikumBraunschweiggGmbH,Braunschweig,GermanyProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/82010Probst-KepperandBuer;licenseeBioMedCentralLtd.
ThisisanOpenAccessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense(http://creativecommons.
org/licenses/by/2.
0),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
andregulatoryfunctions,isthepresenceofaTreg-speci-fichigher-orderregulatorynetwork[13,14,23].
Thepos-sibilitythatTreg-specificcontrolmechanismscanmaintainsustainedhighlevelsofFOXP3andcancon-troltheregulatoryfunctionhasbeenaddressedonlyrecentlywiththeidentificationoftheglycoprotein-Arepetitionspredominant(GARPorLRRC32)receptor[21,24-28].
IdentificationandcharacterizationofGARPasasafeguardofFOXP3GARPwasidentifiedbasedontheanalysisofgeneexpressionprofilingofTregandThcellsfollowingTCRstimulation,sinceTCRstimulationdoesleadtotheinductionoftheirmutuallyexclusivefunctions[21,24].
GARPisspecificallyinducedinCD4+CD25hiFOXP3hiTregcellsandthusisaTreg-specificactivationmarker[21,24-27].
BecausetheexpressionofGARPisup-regu-latedinFOXP3-transducedThcells,GARPobviouslydependsonFOXP3,andthisfindingsuggestsapotentialcontributiontotheregulatoryphenotype[21,29].
ThefunctionofGARPhasbeenelucidatedbyectopicover-expressioninhumanalloantigen-specificThcellsanddown-regulationofGARPinhumanantigen-speci-ficTregcells[21,29].
Retroviralover-expressionofGARPinThcells,aftersomeroundsofTCRstimulation,leadstoanefficientandstablereprogramming/transdifferen-tiationoftheestablishedeffectortowardtheregulatoryprogram.
ThisfindingisassociatedwithconstitutiveexpressionofFOXP3,theb-galactosidebindingproteinlectin,galactoside-binding,soluble,3(LGALS3)[8,30],andthecysteine-endoproteaselegumain(LGMN)[8]andwithanextendedTreg-signaturewithsuppressionofeffectorcytokineproductionandacquisitionofregula-toryfunctionssimilartothoseofTregcells[21,29].
Thus,aFOXP3-regulatinggenehasbeenidentifiedinthehumansystem,andthisfindingsuggeststhattheGARPsignalingpathwaymayhavedirecttherapeuticapplications[28,31]similartothosethathavebeendescribedforCD83inthemurinesystem[32].
Incontrast,lentiviraldown-regulationofGARPinhumanalloantigen-specificTregcellsbyspecificsmallinterferingRNA(siRNA)substantiallyimpairssuppres-sorfunctionandFOXP3expressionthatisassociatedwithimpairedinductionofCD83andCD27,bothknowntoregulateFOXP3[21,32,33].
Morestrikingisthefactthatsimilarchangesareinducedbythedown-regulationofFOXP3inTregcells,afindingthatpro-videscompellingevidenceforaGARP-FOXP3positivefeedbackloopinTregcells.
BecausethisfeedbackloopseemstobeinterrelatedwithotherFOXP3-regulatingsystemssuchasCD83andCD27,theexistenceofahigher-orderregulatorynetworkasdiscussedrecentlybyHori[13],canbespeculated(Figure1a).
Thus,GARPisaspecificmarkerofactivatedTregcellsandcanexplainthequalitativeandquantitativediffer-encesinFOXP3expressionandfunctioninTregcellsandThcells.
LackofGARPexpressionfurtherdiffer-entiatesandexplainsthetransientnatureofTGF-b-inducediTregcells[19],suggestingthatnaturalandiTregcellsmayrepresentalternativedifferentiationstagesofsuppressorcells[21,26].
Inlinewiththeseobservations,aspecificallyhypomethylatedregioninintron1ofGARPandtwodifferentiallymethylatedregionswithenhancerfunctionsinTregcellshaverecentlybeenchar-acterized.
Thesefindingshaveidentifiedanepigeneticbasisforthelineage-specificdifferenceinGARPexpres-sion[34].
GARPbringslatentTGF-bintoanewgameMembersoftheTGF-bfamilyarepleiotropiccytokineswithcrucialfunctionsindifferentiation,morphogenesis,andimmunehomeostasis.
TheirfunctioninimmunehomeostasisisevidencedbythefactthatdysregulationofTGF-bfunctionsisassociatedwithautoimmunity[35].
Likemanyothercelltypes,humanTregandThcellscansecretelatentTGF-b[20,36].
However,latency-associatedpeptide(LAP)preventstheactivationoflatentTGF-btowardtheactivematureTGF-b[37].
TheselectiveinductionofLAPandtheactivationofactiveTGF-buponTCRstimulationhasbeenreportedonlyforhumanTregcellsandclones[20,37,38].
ThisfindingfurtherexplainstheTGF-bspecifictranscrip-tionalsignatureanddetectionofexpressionofphos-phorylatedSMAD2inTregcellsofhumanandmurineorigin[20,23,37,39].
Moreover,specificup-regulationofLAPonactivatedhumanTregcellshasbeenshowntoallowimprovementsinthepurityofTregcellisolationproceduresbyseparatingactivatedLAP+FOXP3+TregcellsfromcontaminatingeffectorLAP-FOXP3+/loThcells[38].
Thus,besidesbeingamarkerofactivatedTregcellsincomplexwithLAP,TGF-b1isanimportantmodulatorofFOXP3expression[19,21,40],andapoten-tialmediatorofinfectioustolerancebyitsactionincon-vertingFoxP3-murineCD4+TcellsintofunctionalFoxP3+iTregcells[41].
Theissueofcell-surfacebindingofLAP/latentTGF-bonhumanTregcellshasbeenaddressedonlyrecentlywiththeidentificationofGARPasareceptorofthiscomplex[26,27].
Therefore,twoimportantregulatorycircuitsofTregcellscometogether:theGARP-FOXP3feedbackloopandtheautocrineTGF-bloop(Figure1b).
Withthat,thepotentialsynergyofmanyoftheTregsignaturecomponentsthatareessentialfortheregula-torypropertiesthathavebeenascribedtoTCRactiva-tion,interleukin-2,TGF-b,andFOXP3itself[20,23]couldbeexplainedbythisparticularspatiotemporalinterplayofinterrelatedsignalingsystemsonTregcells.
Probst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page2of6Figure1GARPassafeguardoftheregulatoryphenotype.
(A)Qualitative(lineage-specific)andquantitative(dose-effect)differencesinFOXP3expressioninhumanhelperTcells(Th;upperpanel)andregulatoryTcells(Treg;lowerpanel)areduetolineage-specificmethylationoftherespectiveloci(indicatedbyblackdots)andthustheexpressionofthegenesFOXP3andGARP.
InhumanTregcells,apositivefeedbackloophasbeenfoundbetweenGARPandFOXP3;thisfeedbackloopisinterrelatedwiththeFOXP3-enhancingmoleculesindicated.
PhosphorylationofLGALS3(indicatedbyaP)hasbeenreportedtobeessentialfortheFOXP3-regulatingfunction[21].
GARPisareceptorforLAP/latentTGF-b[26,27].
T-bet(T-boxexpressedinTcells),GATA3(GATA-bindingprotein3),RORg(retinoic-relatedorphanreceptorgamma)representtranscriptionfactorsofTh1,Th2,andTh17cells.
(B)ImplicationsforhumanandmurineTcells,respectively,oftheautocrineandparacrineeffectsofGARPandNrp1surface-boundLAP/latentTGF-bafteractivationofTGF-b.
TheTGF-bsignaturephospho-SMAD2(pSMAD2)hasbeenobservedinhuman(GARP+)andmurine(Nrp1+)Tregcells.
Paracrineeffectsincludethegenerationofinfectioustolerance.
(C)StructuralcompositionoftheLAP/latentTGF-bbindingproteinsNrp1andGARP(LRR,leucine-richrepeatdomain;CUB,complementsubcomponentsC1r/C1sdomain;F5/8coagulationfactordomain;MAM,meprin,A5,andreceptorprotein-tyrosinphosphataseμdomain;TM,transmembraneregion;L,leaderpeptide).
NIP(Nrp1interactingprotein)isaNrp1bindingproteininvolvedintheregulationofNrp1-mediatedsignalingasamolecularadapter[48].
Probst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page3of6Perspective:doesNrp1representafunctionalhomologueofGARPinmurineTregcellsTheidentificationofGARPasareceptorforLAP/latentTGF-bopensspeculationaboutapotentialcommondenominator.
Thereasonforsuchspeculationisthatneuropilin1(Nrp1),whichhasbeencharacterizedasamarkerofCD4+CD25+TregcellsinmicethatenhancesTregcell/dendriticcellcontactduringantigenrecogni-tion[42,43],hasalsobeencharacterizedasareceptorforLAP/latentTGF-b[39].
Moreover,murinesortedNrp1-TcellscapturesolubleNrp1(appliedasacon-stantfragment[Fc]-fusionprotein),andthecapturedNrp1increasestheirabilitytobindLAP/TGF-b1.
SuchcoatedTcellsacquirestrongregulatoryactivity[39].
Thus,Nrp1isaTGF-b1receptorthat,unlikeGARP[27],alsoactivatesthelatentformofTGF-b1.
ThestructuraldifferencesbetweenGARP,aToll-likereceptorhomologuewithleucine-richrepeats,andthemulti-domainproteinNrp1,areceptorforclass-3sema-phorin-familyproteinsandvascularendothelialgrowthfactor(Figure1c)[44],necessitatefurtherbiochemicalandmolecularanalysestoidentifyspecificbindinginter-actionsandpotentiallyassociatedmolecules.
TheissueofGARPexpressioninmurineTregcellsattheproteinlevelremainstobeelucidated.
DiscussionsOpenQuestionsConcerningtheFunctionofGARPBecauseGARPisconstitutivelyexpressedonplatelets[26,45],andbecauseapotentialfunctionofGARPonthrombusformationhasrecentlybeenreported[46],importantquestionsaboutGARPsignalingandparallelfunctioninplateletscomparedtoTregcellscouldbeconsidered.
ConcerningthedependenceofGARPexpressiononFOXP3asdescribedabove,ithasbeenreportedthatFOXP3isexpressedbyhumanandmurinemegakaryocytes[47].
Therefore,thethrombocytopeniaandplateletabnormalitiesexperiencedbysomepatientswithIPEXsyndromecanbeexplainedbylossoffunc-tionofFOXP3[47];however,thisexplanationwouldsuggestaconcomitantimpairmentofGARPexpressionandfunctiononIPEXplatelets,animpairmentthathasnotyetbeenshown.
Acontroversialissueisthepotentialsuppressorfunc-tionofGARP,suggestedrecently[24],becauseplateletsasanaturalsourceofGARP-expressingcellsdonotfunctionassuppressorcells[21].
Therefore,differencesinthefunctionofGARPinplateletsandTregcellscanbesuggested.
ThisquestionisimportantforthepotentialdesignofGARP-selectivedrugsthatcanspecificallytar-getonlyTregcellsandnotplateletfunctions.
Asofnow,neithertheligandnorthesignalingsystemorpotentialco-receptor(s)ofGARPhasbeenidentified,andidentify-ingthemisthemostimportantchallengeforthefuture.
ConclusionsTheidentificationofGARPasalineage-specifickeyreceptorofhumanactivatedTregcells,whichisinpartcontrolledbylineage-specifichypomethylationoftheGARPlocus,thecharacterizationofaGARP-FOXP3positivefeedbackloopthatsafeguardsFOXP3expres-sioninTregcells,andthebindingofLAP/latentTGF-btoGARPprovideaconceptualframeworkforanewmoleculardefinitionoftheregulatoryprogram.
IfGARPisareceptorforthewell-knownimmunemodulatorTGF-bonhumanTregcells,andifNrp1playsthissameroleonmurineTregcells,thenthissimilaritymightexplainthesimilaritiesintheTGF-bsignaturesthathavebeenobservedinTregcellsinbothspecies.
ThesurfacebindingandactivationofTGF-bhaveobviousimplicationsforinfectioustolerance.
Completeelucida-tionoftheGARP/GARP-ligandsignalingsysteminTregcellsandplateletsisanimportantchallengeandaprere-quisiteforthefuturedevelopmentofstrategiesandtoolsforinducingorinhibitingTregcellsinchronicinfection,tumorimmunotherapy,autoimmunediseases,andtransplantation.
ListofabbreviationsusedGARP:glycoprotein-Arepetitionspredominant;IPEX:immunedysregulation,polyendocrinopathy,enteropathy,X-linked;iTregcells:inducedregulatoryTcells;LAP:latency-associatedpeptide;Nrp1:neuropilin1;SMAD:Sma-andMad-relatedprotein2;TCR:T-cellreceptor;TGF-b:transforminggrowthfactor-b;Thcells:helperTcells;Tregcells:regulatoryTcells.
Reviewers'commentsReviewer'sreport1Reviewer1:Dr.
JimDiSanto,CytokinesandLymphoidDevelopmentLab,InstitutPasteur,Paris,FranceReviewer'scomment:IhavereadyourcommentforBiologyDirectentitled"FOXP3andGARP(LRRC32):themasteranditsminion".
IfindthiscommenttobeinterestingandsuitableforpublicationinBiologyDirect.
Idonothaveanyspecificcommentsforwebpublication.
Reviewer'sreport2Reviewer2:Dr.
BeneditaRocha,InstitutNationaldelaSantéetdelaRechercheMédicale(INSERM)U591,Insi-tutNecker,FranceReviewer'scomment:Regulatorycellshaveafunda-mentalroleinmanydiseaseprocesses,andextensiveexperimentalandclinicaldataindicatethattoolspre-ventingorincreasingregulatoryfunctionwillhaveafundamentaltherapeuticrole.
WhileFOXP3expressiongenerallycorrelateswithregulationinthemouse,thisisnotsoinhumanTcells.
ThiscommentreviewsaProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page4of6fundamentalaspect,thefactorsbesidesFOXP3expres-sionthatensuretheinductionofastableregulatoryfunctiononhumancells,theircorrelationwithFOXP3regulationandtheirpossiblemechanismsofaction.
Ifoundthetopicactualandimportant,thecommentclearandcomprehensiveandstronglysupportpublication.
Reviewer'sreport3Reviewer3:Dr.
WernerSolbach,InsituteforMedicalMicrobiologyandHygiene,UniversityLübeck,GermanyReviewer'scomment:Thems.
dealswiththeconnec-tivityofFOXP3and"glycoprotein-Arepititionspredo-minantreceptor(GARPorLRRC32)inthecontextofthefunctioningofregulatoryTcells(Tregs).
ThistopicisofgreatrelevanceinthecontextofclarifyingtheequivocalroleofFOXP3anditspartnersforexplanationofregulatoryTcellcircuits.
ItisclearthatnotonlyFOXP3orGARPalone,butalsolatentlyactivatedTGF-biscrucialforthesuppressiveactivityofTregcells.
TheauthorsnowverynicelybringtogethertheGARP-FOXP3regulatorycircuitwiththeautocrineTGF-bloopwhichhelpstoexplainmanyTregfeatures.
Intheirperspective,theyalsotrytoopenthoughtfulavenueshowtobringtogether(human)GARPwithitspossiblefunctionalhomologueinmice,neuropilin1.
Insum-mary,theypresentavaluableconceptualframeworkforunderstandingtheregulatoryprogramintheTcellreac-tivitysystemandbeyond.
Thems.
iswellwrittenandeasytounderstand.
IrecommendpublicationinBiologyDirect.
AcknowledgementsMichaelProbst-KepperwassupportedbygrantsfromtheVolkswagenStiftung(I/73234)andtheDeutscheForschungsgemeinschaft(PR554/2).
Authordetails1InstituteforMicrobiology,ImmunologyandHygiene,StdtischesKlinikumBraunschweiggGmbH,Braunschweig,Germany.
2InstituteforMedicalMicrobiology,UniversityHospitalEssen,Essen,Germany.
Authors'contributionsMPKandJBbothwereinvolvedindraftingofthemanuscriptandapprovedthefinalversiontobepublished.
CompetinginterestsTheauthorsdeclarethattheyhavenocompetinginterests.
Received:27January2010Accepted:5February2010Published:5February2010References1.
ZieglerSF:FOXP3:OfMiceandMen.
AnnuRevImmunol2006,24:209-226.
2.
GambineriE,TorgersonTR,OchsHD:Immunedysregulation,polyendocrinopathy,enteropathy,andX-linkedinheritance(IPEX),asyndromeofsystemicautoimmunitycausedbymutationsofFOXP3,acriticalregulatorofT-cellhomeostasis.
CurrOpinRheumatol2003,15:430-435.
3.
KhattriR,CoxT,YasaykoSA,RamsdellF:AnessentialroleforScurfininCD4+CD25+Tregulatorycells.
NatImmunol2003,4:337-342.
4.
FontenotJD,RasmussenJP,WilliamsLM,DooleyJL,FarrAG,RudenskyAY:RegulatoryTcelllineagespecificationbytheforkheadtranscriptionfactorfoxp3.
Immunity2005,22:329-341.
5.
LinW,HaribhaiD,RellandL,TruongN,CarlsonM,WilliamsC,ChatilaT:RegulatoryTcelldevelopmentintheabsenceoffunctionalFoxp3.
NatImmunol2007,8:359-368.
6.
HoriS,NomuraT,SakaguchiS:ControlofregulatoryTcelldevelopmentbythetranscriptionfactorFoxp3.
Science2003,299:1057-1061.
7.
FontenotJD,GavinMA,RudenskyAY:Foxp3programsthedevelopmentandfunctionofCD4+CD25+regulatoryTcells.
NatImmunol2003,4:330-336.
8.
OcklenburgF,Moharregh-KhiabaniD,GeffersR,JankeV,PfoertnerS,GarritsenH,GroebeL,KlempnauerJ,DittmarKE,WeissS,BuerJ,Probst-KepperM:UBD,adownstreamelementofFOXP3,allowstheidentificationofLGALS3,anewmarkerofhumanregulatoryTcells.
LabInvest2006,86:724-737.
9.
WanYY,FlavellRA:IdentifyingFoxp3-expressingsuppressorTcellswithabicistronicreporter.
PNAS2005,102:5126-5131.
10.
WilliamsLM,RudenskyAY:MaintenanceoftheFoxp3-dependentdevelopmentalprograminmatureregulatoryTcellsrequirescontinuedexpressionofFoxp3.
NatImmunol2007,8:277-284.
11.
WanYY,FlavellRA:RegulatoryT-cellfunctionsaresubvertedandconvertedowingtoattenuatedFoxp3expression.
Nature2007,445:766-770.
12.
AllanSE,PasseriniL,BacchettaR,CrellinN,DaiM,OrbanPC,ZieglerSF,RoncaroloMG,LevingsMK:Theroleof2FOXP3isoformsinthegenerationofhumanCD4Tregs.
JClinInvest2005,115:3276-3284.
13.
HoriS:RethinkingthemoleculardefinitionofregulatoryTcells.
EurJImmunol2008,38:928-930.
14.
RoncaroloMG,GregoriS:IsFOXP3abonafidemarkerforhumanregulatoryTcells.
EurJImmunol2008,38:925-927.
15.
GavinMA,TorgersonTR,HoustonE,deRoosP,HoWY,Stray-PedersenA,OcheltreeEL,GreenbergPD,OchsHD,RudenskyAY:Single-cellanalysisofnormalandFOXP3-mutanthumanTcells:FOXP3expressionwithoutregulatoryTcelldevelopment.
ProcNatlAcadSciUSA2006,103:6659-6664.
16.
AllanSE,CromeSQ,CrellinNK,PasseriniL,SteinerTS,BacchettaR,RoncaroloMG,LevingsMK:Activation-inducedFOXP3inhumanTeffectorcellsdoesnotsuppressproliferationorcytokineproduction.
IntImmunol2007,19:345-354.
17.
FranoisV,OttavianiS,RenkvistN,StockisJ,SchulerG,ThielemansK,ColauD,MarchandM,BoonT,LucasS,BruggenvanderP:TheCD4+T-CellResponseofMelanomaPatientstoaMAGE-A3PeptideVaccineInvolvesPotentialRegulatoryTCells.
CancerRes2009,69:4335-4345.
18.
WangF,Ioan-FacsinayA,VoortvanderEIH,HuizingaTW,ToesRE:TransientexpressionofFOXP3inhumanactivatednonregulatoryCD4+Tcells.
EurJImmunol2007,37:129-138.
19.
TranDQ,RamseyH,ShevachEM:InductionofFOXP3expressioninnaivehumanCD4+FOXP3-TcellsbyTcellreceptorstimulationisTGF{beta}-dependentbutdoesnotconferaregulatoryphenotype.
Blood2007,110:2983-2990.
20.
StockisJ,FinkW,FrancoisV,ConnerotteT,deSmetC,KnoopsL,BruggenvanderP,CouliePG,LucasS:ComparisonofstablehumanTregandThclonesbytranscriptionalprofiling.
EurJImmunol2009,39:869-882.
21.
Probst-KepperM,GeffersR,KrgerA,ViegasN,ErckC,HechtHJ,LünsdorfH,RoubinR,Moharregh-KhiabaniD,WagnerK,OcklenburgF,JeronA,GarritsenH,ArstilaTP,KeklinenE,BallingR,HauserH,BuerJ,WeissS:GARP:akeyreceptorcontrollingFOXP3inhumanregulatoryTcells.
JournalofCellularandMolecularMedicine2010,13:3343-3357.
22.
TakakiH,IchiyamaK,KogaK,ChinenT,TakaesuG,SugiyamaY,KatoS,YoshimuraA,KobayashiT:STAT6InhibitsTGF-b1-mediatedFoxp3InductionthroughDirectBindingtotheFoxp3Promoter,WhichIsRevertedbyRetinoicAcidReceptor.
JBiolChem2008,283:14955-14962.
23.
HillJA,FeuererM,TashK,HaxhinastoS,PerezJ,MelamedR,MathisD,BenoistC:Foxp3Transcription-Factor-Dependentand-IndependentRegulationoftheRegulatoryTCellTranscriptionalSignature.
Immunity2007,27:786-800.
24.
WangR,WanQ,KozhayaL,FujiiH,UnutmazD:IdentificationofaRegulatoryTcellspecificCellSurfaceMoleculethatMediatesProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page5of6SuppressiveSignalsandInducesFoxp3Expression.
PLoSOne2008,3:e27705.
25.
WangR,KozhayaL,MercerF,KhaitanA,FujiiH,UnutmazD:ExpressionofGARPselectivelyidentifiesactivatedhumanFOXP3+regulatoryTcells.
PNAS2009,106:13439-13444.
26.
TranDQ,AnderssonJ,WangR,RamseyH,UnutmazD,ShevachEM:GARP(LRRC32)isessentialforthesurfaceexpressionoflatentTGF-bonplateletsandactivatedFOXP3+regulatoryTcells.
ProcNatlAcadSciUSA2009,106:13445-13450.
27.
StockisJ,ColauD,CouliePG,LucasS:MembraneproteinGARPisareceptorforlatentTGF-bonthesurfaceofactivatedhumanTreg.
EurJImmunol2009,39:3312-3322.
28.
Probst-KepperM,KrgerA,GarritsenHSP,BuerJ:PerspectivesonRegulatoryTCellTherapies.
TransfusMedHemother2009,36:302-308.
29.
Probst-KepperM,BallingR,BuerJ:FOXP3:RequiredbutNotSufficient.
TheRoleofGARP(LRRC32)asaSafeguardoftheRegulatoryPhenotype.
CurrMolMed2010.
30.
PfoertnerS,JeronA,Probst-KepperM,GuzmanCA,HansenW,WestendorfAM,ToepferT,SchraderAJ,FranzkeA,BuerJ,GeffersR:SignaturesofHumanRegulatoryTCells:AnEncounterwithOldFriendsandNewPlayers.
GenomeBiology2006,7:R54-1-R54-18.
31.
TranDQ,ShevachEM:TherapeuticpotentialofFOXP3regulatoryTcellsandtheirinteractionswithdendriticcells.
HumImmunol2009,70:294-299.
32.
ReinwaldS,WietheC,WestendorfAM,BreloerM,Probst-KepperM,FleischerB,SteinkassererA,BuerJ,HansenW:CD83ExpressioninCD4+TCellsModulatesInflammationandAutoimmunity.
JImmunol2008,180:5890-5897.
33.
YangZZ,NovakAJ,ZiesmerSC,WitzigTE,AnsellSM:CD70+non-HodgkinlymphomaBcellsinduceFoxp3expressionandregulatoryfunctioninintratumoralCD4+CD25Tcells.
Blood2008,110:2537-2544.
34.
SchmidlC,KlugM,BoeldTJ,AndreesenR,HoffmannP,EdingerM,RehliM:Lineage-specificDNAmethylationinTcellscorrelateswithhistonemethylationandenhanceractivity.
GenomeRes2009,19:1165-1174.
35.
WanYY,FlavellRA:TGF-betaandregulatoryTcellinimmunityandautoimmunity.
JClinImmunol2009,28:647-659.
36.
LevingsMK,SangregorioR,SartiranaC,MoschinAL,BattagliaM,OrbanPC,RoncaroloMG:HumanCD25+CD4+Tsuppressorcellclonesproducetransforminggrowthfactorbeta,butnotinterleukin10,andaredistinctfromtype1Tregulatorycells.
JExpMed2002,196:1335-1346.
37.
NakamuraK,KitaniA,FussI,PedersenA,HaradaN,NawataH,StroberW:TGF-beta1playsanimportantroleinthemechanismofCD4+CD25+regulatoryTcellactivityinbothhumansandmice.
JImmunol2004,172:834-842.
38.
TranDQ,AnderssonJ,HardwickD,BebrisL,IlleiGG,ShevachEM:Selectiveexpressionoflatency-associatedpeptide(LAP)andIL-1receptortypeI/II(CD121a/CD121b)onactivatedhumanFOXP3+regulatoryTcellsallowsfortheirpurificationfromexpansioncultures.
Blood2009,113:5125-5133.
39.
GlinkaJ,Prud'hommeGJ:Neuropilin-1isareceptorfortransforminggrowthfactor-1,activatesitslatentform,andpromotesregulatoryTcellactivity.
JLeukocBiol2008,84:302-310.
40.
FantiniMC,BeckerC,MonteleoneG,PalloneF,GallePR,NeurathMF:CuttingEdge:TGF-betaInducesaRegulatoryPhenotypeinCD4+CD25-TCellsthroughFoxp3InductionandDown-RegulationofSmad7.
JImmunol2004,172:5149-5153.
41.
AnderssonJ,TranDQ,PesuM,DavidsonTS,RamseyH,O'SheaJJ,ShevachEM:CD4FoxP3regulatoryTcellsconferinfectioustoleranceinaTGF-beta-dependentmanner.
JExpMed2008,205:1975-1981.
42.
BruderD,Probst-KepperM,WestendorfAM,GeffersR,BeissertS,LoserK,vonBoehmerH,BuerJ,HansenW:Frontline:Neuropilin-1:asurfacemarkerofregulatoryTcells.
EurJImmunol2004,34:623-630.
43.
SarrisM,AndersenKG,RandowF,MayrL,BetzAG:Neuropilin-1ExpressiononRegulatoryTCellsEnhancesTheirInteractionwithDendriticCellsduringAntigenRecognition.
Immunity2008,28:402-413.
44.
GerettiE,KlagsbrunM:Neuropilins:NovelTargetsforAnti-AngiogenesisTherapies.
CellAdhMigr2007,1:56-61.
45.
MacaulayIC,TijssenMR,Thijssen-TimmerDC,GusnantoA,StewardM,BurnsP,LangfordCF,EllisP,DudbridgeF,ZwagingaJJ,WatkinsNA,SchootvanderCE,OuwehandWH:Comparativegeneexpressionprofilingofinvitrodifferentiatedmegakaryocytesanderythroblastsidentifiesnovelactivatoryandinhibitoryplateletmembraneproteins.
Blood2007,109:3260-3269.
46.
O'ConnorN,SallesI,CvejicA,WatkinsNA,WalkerA,GarnerS,MacaulayIC,StewardM,ZwagingaJ,BrayS,DudbridgeF,deBonoB,GoodallAH,DeckmynH,StempleDL,OuwehandWH,BloodomicsConsortium:Functionalgenomicsinzebrafishpermitsrapidcharacterizationofnovelplateletmembraneproteins.
Blood2008,113:4754-4762.
47.
BernardJJ,SeweryniakKE,KoniskiAD,SpinelliSL,BlumbergN,FrancisCW,TaubmanMB,PalisJ,PhippsRP:Foxp3RegulatesMegakaryopoiesisandPlateletFunction.
ArteriosclerThrombVascBiol2009,29:1874-1882.
48.
CaiH,ReedRR:CloningandCharacterizationofNeuropilin-1-InteractingProtein:APSD-95/Dlg/ZO-1Domain-ContainingProteinThatInteractswiththeCytoplasmicDomainofNeuropilin-1.
JNeurosci1999,19:6519-6527.
doi:10.
1186/1745-6150-5-8Citethisarticleas:Probst-KepperandBuer:FOXP3andGARP(LRRC32):themasteranditsminion.
BiologyDirect20105:8.
SubmityournextmanuscripttoBioMedCentralandtakefulladvantageof:ConvenientonlinesubmissionThoroughpeerreviewNospaceconstraintsorcolorgurechargesImmediatepublicationonacceptanceInclusioninPubMed,CAS,ScopusandGoogleScholarResearchwhichisfreelyavailableforredistributionSubmityourmanuscriptatwww.
biomedcentral.
com/submitProbst-KepperandBuerBiologyDirect2010,5:8http://www.
biology-direct.
com/content/5/1/8Page6of6
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