Ahallmarkoftheimmunesystemisitsabilitytomountamoreeffectiveandrapidresponseagainstsecondary exposuretoapathogen.Themechanismsbywhichtheadaptiveimmunesystemaccomplishesthistask centeraroundDNArearrangementsandselectionofthemosteffectively-respondingcells.However,ithas recentlybecomeevidentthatinnateimmunecellsalsoexhibitmemory,andthatunlikeadaptiveimmunecells, innateimmunecellscanexhibitmemorytowardsdifferentpathogensaswellasthesameoneencountered duringtheinitialexposure.Thisprocess,calledtrainedimmunity,canpresentasenhancedprotectionfrom heterologousinfectionfollowingvaccination.Ontheotherhand,diseasescharacterizedbyinflammationmay beexacerbatedbytheinductionoftrainedimmunity.Preliminaryworkfromourlabaswellasothers?has suggestedthattrainedimmunityisdrivenbyalteredtranscriptionalresponses,withinheritedchromatin structuresplayinganimportantroleinpropagatingmemoryacrosscelldivisions.Ourstudieshavedefineda subsetofgenesthatdisplaymorerapidinductionuponasecondexposuretoastimulusinalymphocyte-to- macrophagetransdifferentiationmodel.These?memory?genesdisplayareductionintrimethylationoflysine 27ofhistoneH3(H3K27me3),andinhibitingH3K27me3demethylationresultsinimpairedmemoryformation attheseloci.Wehaveundertakenapilotunbiasedscreenforadditionalchromatinfactorsthatcouldinfluence memoryformation,andhaveidentified23genesthatscoredhighlyandarecurrentlybeingvalidated. Inthiswork,weplantoextendourfindingstomacrophagesandNKcells,twocelltypesoftheinnateimmune systemthoughttoexhibitmemory.Wewillestablishprotocolstoelicitamemoryresponseinthesecells,using stimulithatmimicpathogenexposureorcytokinesignaling,andexaminewhichgenesexhibitmemoryineach context.Usingchromatinimmunoprecipitationapproaches,wewillidentifychromatinmodificationsthat accompanytheinductionoftranscriptionalmemory,andwewillemploysmall-moleculeandshRNA-based screeningapproachestoidentifychromatinregulatorsresponsiblefortheestablishmentormaintenanceof memory.Finally,wewillextendourresultstoamousemodelofdiet-inducedobesity,apathologyexacerbated byinflammationofadiposetissuesbypro-inflammatorymacrophageactivity.Wewillexaminewhether macrophagetranscriptionalmemoryplaysaroleinasecondinductionofobesityfollowingaperiodofweight loss.Weexpectourstudiestoelucidatethechromatin-basedmolecularmechanismsunderlyingthe establishmentandmaintenanceoftranscriptionalmemory,andrevealhowthesemechanismsplayarolein thepathologicalcontextofdiet-inducedobesity.

Public Health Relevance

Justlikeweashumanscanlearnfrompastexperiences,cellswithinourbodyalsohavethecapabilitytolearn afterexposuretovariousstimuliandtomaintainthismemorytoallowforcellularadaptation.Forexample,as cellsoftheimmunesystemfightoffnewinfections,theylearnfromthisexposuretoenableaquickerand betterresponseinthefuture.Intheproposedsetofexperiments,wewillexplorethedifferentmolecules involvedinestablishingcellularmemory,andhopetoexplainhowmemorycanbothhelphumansmorereadily fightdisease,andalsocontributetopathologiessuchasobesity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21AI130737-01
Application #
9296235
Study Section
Cellular and Molecular Immunology - A Study Section (CMIA)
Program Officer
Jiang, Chao
Project Start
2017-01-18
Project End
2018-12-31
Budget Start
2017-01-18
Budget End
2017-12-31
Support Year
1
Fiscal Year
2017
Total Cost
$265,500
Indirect Cost
$115,500
Name
Boston Children's Hospital
Department
Type
Independent Hospitals
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
02115