The effect of dietary lipid manipulation on rat lymphocyte subsets and proliferation

Polyunsaturated fatty acids (PUFA) have been shown to suppress immune cell functions in vitro. DietarystudiesinvestigatingtheeffectsofPUFA-containingoilson lymphocytefunctionshave yieldedcontradictoryfindings:suchstudiesare difficulttocompare as thereare many variationsin protocols. The present study investigated the effects of diets containing oils rich in saturated fatty acids,monounsaturatedfattyacids,n-6PUFA or n-3PUFA on ratlymphocyteproliferationand on receptorandsurfacemarkerexpression.Ratswere fedfor10weekson a low-fat(LF)diet (approximately2% fatbyweight)or on one offivehigh-fatdiets,whichcontained20% (by weight) hydrogenated coconut oil (HCO), olive oil (00), safflower oil (SO), evening primrose oil (EPO)or menhaden(fish)oil(MO).ComparedwithfeedingtheLF diet,allofthehigh-fatdiets suppressedtheproliferationoflymphocytesfromthespleen:althoughtherewas no significant effectofdieton theproliferationoflymphocytesfromthethymus,therewas a trendtowards decreasedproliferationwithhigh-fatfeeding.Feedingthe00, EPOorMOdietssignificantly suppressed proliferation of mesenteric lymph node lymphocytes compared with feeding the LF, HCO or SO diets.Dietarylipidmanipulationhadno effecton theproportionofT cels,B cellsor monocytes/macrophagesinthespleen,thymusor lymphnodes.Dietarylipidmanipulationalso hadno significanteffecton theproportionsofCD4+ or CD8+ lymphocytesinspleen,thymusor lymphnodes,eitherinfreshlypreparedcellsor incellsculturedinthepresence ofmitogen.There were no significanteffectsofdietarylipidmanipulationon theexpressionofIL-2receptorsor transferrin receptorsbyconcanavalinA (ConA)-stimulatedlymphocytes.However,therewas a trendtowards a decreaseintransferrinreceptorexpressionbyConA-stimulatedlymphocytesfromthethymusand lymphnodesoftheMO-fedratsandtowardsa decreaseintheexpressionofIL-2receptorsby lymphocytes from the spleens and thymi of the MO-fed rats. These observations provide evidence thatsome dietaryoils,particularly00, EPOandMO,possessimmunosuppressivepropertiesand so may beusefulinthetherapyofdiseasesinvolvinginappropriatelymphocyteactivation.