Histone-H3-AbELISAisasolidphaseenzymeimmunoassaywithhumannativehistoneH3isolatedfromtheeukaryoticcellineHeLaforthequantitativedetectionofantibodiesagainstH3inhumanserum.Theassayisatoolinthedifferentialdiagnosisofsystemiclupuserythematosus(SLE).Histonesaresmallbasicproteinsof11to21kDaconstitutingasetofinteractingproteinsthatorganizeandconstrainthetopologyofDNAinmosteukaryoticcellsintoaparticlecallednucleosome.InthisparticlethefourhistonesH2A,H2B,H3andH4formanoctamer(H2A,H2B,H3,H4)2aroundwhich146bpofdsDNAiswrappedby13/4turns.HistoneH1interactswiththenucleosomeandtogetherwithlinked-DNAconnectsneighboringnucleosomes.AntibodiesagainsthistonesoccurinpatientswithSLEwithafrequencyof50%,duringactivephasesofSLEwithanevenhigherfrequency(80%).TheyarenotspecificforSLE,especiallywhennotassociatedwithanti-dsDNAantibodies.Theyarealsofoundinotherinflammatoryrheumatoiddiseases,likerheumatoidarthritis(lowtitersandmainlyagainstH1),orsystemicsclerosisandjuvenilechronicarthritis.Moreovertheseantibodiesarefoundinprimarybiliarycirrhosis(upto70%)andautoimmunehepatitis(upto35%),too.Anti-histoneantibodies,intheabsenceofantibodiestodsDNA,doplayanimportantroleinthediagnosisofdrug-inducedLEbeingfoundin95%ofcases.Thesedrugsareinducingjointandskinsymptoms,aswellasthedifferentanti-histonespecificities,whileneverrenalmanifestations.Anti-histoneantibodiesindrug-inducedLEaretemporaryanddisappearwithinafewmonthsafterwithdrawaloftheinducingdrug.