OX40ListheligandforCD134andisexpressedonsuchcellsasDC2senablingamplificationofTh4celldifferentiation.OX40LhasalsobeendesignatedCD252.Byanalysisofaninterspecificbackcross,themouseTnfsf4geneismappedtochromosome1.Usingfluorescenceinsituhybridization,theylocalizedthehumanTNFSF4geneto1q25,aregionsharinghomologyofsyntenywiththeportionofmousechromosome1containingtheTnfsf4gene.OX40LstronglyinhibitedthegenerationofIL-10-producingTr1cellsinducedbytwophysiologicstimuli,theinduciblecostimulatoryligandandimmaturedendriticcells.Inaddition,OX40LstronglyinhibitedIL-10productionandsuppressivefunctionofdifferentiatedIL-10-producingTr1cells.Tnfsf4underliesAth1inmiceandthatpolymorphismsinitshumanhomologTNFSF4increasetheriskofmyocardialinfarctioninhumans.