Medical Microbiology

TheT-CellSystem

T-CellReceptors(TCR)andAccessoryMolecules

LikeBcells,Tcellshavereceptorsthatbindspecificallytotheirstericcounter-
partsonantigenepitopes.ThediversityofT-cellreceptorsisalsoachievedby
meansofgeneticrearrangementofV,D,andJsegments(Fig.2.4b).However,
theT-cellreceptorisneversecreted,andinsteadremainsmembrane-bound.
EachT-cellreceptorconsistsoftwotransmembranechains,ofeither
theaandbforms,orthecanddforms(nottobeconfusedwiththeheavy

TheT-CellSystem 57

TheMucosa-AssociatedLymphoidTissue

(MALT)ImmuneSystemand“Homing”

Fig.2. 5 SpecializedAPCs(Mcellsintheintestinalwallorpulmonarymacro-

phagesinthelung)takeupantigensinmucosaandpresenttheminthePeyer’s

patchesorlocallymphnodes.ThisprobablyenhancesTcell-dependentactivation

ofIgA-producingBcells,whicharepreferentiallyrecruitedtothemucosalregions

(“homing”)vialocaladhesionmoleculesandantigendepots,resultinginatypeof

geographicspecificitywithintheimmuneresponse.

2

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Kayser, Medical Microbiology © 2005 Thieme

All rights reserved. Usage subject to terms and conditions of license.