Human GALT includes the multi-follicular Peyer's patches of the ileum, the vermiform appendix, and the numerous isolated lymphoid follicles (ILF) ...SkiptomaincontentThankyouforvisitingnature.com.YouareusingabrowserversionwithlimitedsupportforCSS.Toobtainthebestexperience,werecommendyouuseamoreuptodatebrowser(orturnoffcompatibilitymodeinInternetExplorer).Inthemeantime,toensurecontinuedsupport,wearedisplayingthesitewithoutstylesandJavaScript.AdvertisementnaturemucosalimmunologyreviewarticlesarticleHumangut-associatedlymphoidtissues(GALT);diversity,structure,andfunctionDownloadPDFAbstractGut-associatedlymphoidtissues(GALT)arethekeyantigensamplingandadaptiveimmuneinductivesiteswithintheintestinalwall.HumanGALTincludesthemulti-follicularPeyer’spatchesoftheileum,thevermiformappendix,andthenumerousisolatedlymphoidfollicles(ILF)whicharedistributedalongthelengthoftheintestine.OurcurrentunderstandingofGALTdiversityandfunctionderivesprimarilyfromstudiesinmice,andtherelevanceofmanyofthesefindingstohumanGALTremainsunclear.HerewereviewourcurrentunderstandingofhumanGALTdiversity,structure,andcompositionaswellastheirpotentialforregulatingintestinalimmune responsesduringhomeostasisandinflammatoryboweldisease(IBD).Finally,weoutlinesomekeyremainingquestionsregardinghumanGALT,theanswerstowhichwilladvanceourunderstandingofintestinalimmuneresponsesandprovidepotentialopportunitiestoimprovethetreatmentofintestinaldiseases.DownloadPDFIntroductionThehumangutcontainsadiversemicrobiotacomprisingapproximately40trillionmicroorganisms1whichprovideessentialbenefitsforhumanhealth,includingpreventionofcolonizationbypathogens2,detoxificationofbileacids3,metabolismofnon-digestiblecarbohydrates4,5andgenerationofkeymetabolitesimportantforhumanhealth6.Theintestinalimmunesystemmustrespondappropriatelytothesebeneficialmicrobeswhileprovidingactiveimmunityagainstinvadingpathogens.Breakdownofthisbalancecanleadtointestinalpathologies,includinginflammatoryboweldiseases(IBD;Crohn’sdisease(CD),andulcerativecolit