Medical Microbiology

againstantigenspresentonthedonorendothelium,resultingincoagulation,

thromboses,andinfarctionswithextensivenecrosis.

&Acuterejection,occurringwithindaysorweeks.Thisisaccompaniedbya
perivascularandprominentoccurrenceofTlymphocyteinfiltrates.Acutere-
jectioncanbepreventedbyimmunosuppression.

&Chronicrejection,occurringwithinmonthstoyears.Thisiscausedby
low-levelchronicT-cellresponses,andcanbemediatedbycellularandhu-
moralmechanisms.Thiscanincludeobliterativevascularintimaprolifera-
tion,vasculitis,toxic,andimmunecomplexglomerulonephritis.

AntigenicityandImmunogenicityofMHCinOrganTransplants

Athyroidglandfromdonor“a,”freshlytransplantedundertherenalcapsuleofan

MHC(H-2)-incompatiblerecipientmouse“b”isacutelyrejected(withinsevento

ninedays).IftheorganistreatedinsuchawayastokillthemigratoryAPCs

andleukocytesbeforeitistransplanted,thentransplant“a”willbeacceptedby

recipient“b”(oftenpermanently).However,shouldfreshspleencells(APCs)

fromdonor“a”betransferredbyinfusion 100 dayslaterintotherecipient“b,”

thepreviouslyacceptedtransplant“a,”cansometimesbeacutelyrejected(i.e.,

within 10 days).

ThisexperimentdemonstratesthatitisnottheMHCantigenspersethatarepo-

tentlyimmunogenic,butratherthattheyonlyshowthisimmunogenicitywhen

theyarelocatedoncellscapableofmigrationtolocallymphnodes.Methodsof

implantingforeigntissuecellsorsmallorgansstrictlyextralymphatically,without

inducingimmuneresponses,arecurrentlyundergoingclinicaltrials(i.e.,withislet

cellsindiabetesandneuronalcellsinparkinsonsdisease).

Methodsofmeasurement.Themainmethodsusedforfollow-upanalysisof

HVGandGVHreactionsarebiopsiesandhistologicalevaluation,evaluationof

bloodcellsandin-vitromixedlymphocytereactions(p. 1 32).

ImmuneDefectsandImmuneResponseModulation..............

&Immunedefectsarefrequentlyacquiredbytherapyorviralinfections,
orasaconsequenceofadvancedage.Inrarecasesimmunedefectscan
alsoresultfromcongenitaldefects,theseincludeseverecombinedimmuno-
deficiency’s(SCID)ortransientpartialimmunedefects(mainlyinvolving
IgAresponses).Immunomodulationcanbeattemptedusinginterleukins
ormonoclonalantibodiesdirectedagainstlymphocytesurfacemolecules
orantigenicpeptides.Immunostimulationisachievedusingadjuvantsor

ImmuneDefectsandImmuneResponseModulation 117

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Kayser, Medical Microbiology © 2005 Thieme

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