ABSTRACT
Brucellaearefacultativeintracellularparasiteswhicharecapableofmultiplicationand survivalwithinhostphagocytes.ThereisevidencethatprotectionfrominfectionandeliminationofBrucellaabortusrequirescell-mediatedimmune(CMI)responses,1•2definedas thoseinwhichTlymphocytesfunctionaseffectorcellsinconferringprotectiveimmunity. AnexampleofaCMIresponseistheactivationofmacrophagesbylymphokinessecreted byimmuneTcells.EarlystudiesdemonstratedinvitrothatacquiredresistancetoB.abortus wasexpressedbyguineapigmacrophages,3andmacrophagesderivedfromimmunized animalshavesubsequentlybeenfoundtoplayanimportantpartinthisprocess.Thereis alsoevidencefrominvitrostudiesandpassivetransferexperiments5· 11thatantibodiesare involvedinprotectiveimmunityandthatantibodiesspecificforthe0-polysaccharidehave aprincipalroleinthisprocess.5 •11
ThemostwidelyusedcorrelatesofCMIarelymphocytestimulation,macrophagemigrationinhibition,anddelayed-typehypersensitivity(DTHskintest)reactions.Thetypes ofsolubleBrucellaantigensusedtomeasureCMIreactionsgreatlyaffecttheresultsofthe measurements.Themostcommonlyusedpreparationsarecomplexmixturesofantigens whichhavebeenextractedfromvariousBrucellacellsbydifferentmethods.Mostcontain alargenumberofproteinsandsomecontainlipopolysaccharide(LPS).Thepresenceof LPScomplicatestheinterpretationofDTHreactionsbothbecauseofitstoxicityandits participationinantibody-mediatedcutaneoushypersensitivity. 12Resultsobtainedfromstudiesonlymphocyte-mediatedimmuneassayshaveusuallycorrelatedmorecloselywithinfectionthanwithprotection.Indeed,theuseofthesemethodshasoftenbeenproposedas adiagnosticprocedure.
