Medical Microbiology

effectorfunction.However,cytotoxicityisonlyoneofseveralimportantfunc-
tionsexpressedbyCD8+Tcells.Theyalsohavemanyothernon-lyticfunc-
tionswhichtheyexecuteviatheproduction,orinductionof,cytokinerelease.
Thedesignation(CD8+)Tsuppressorcellismisleadingandshouldnotbe
used.Itwasoriginallycoinedtodistinguishthesecellsfromthefunction
ofThelpercells,mentionedabove.However,plausibledocumentationofa
suppressoreffectbyCD8+Tcellshasonlybeenobtainedinaverysmall
numberofcases.Inmostcases,thissuppressiveeffectcaninfactbeexplained

TheT-CellSystem 65

InteractionsinT-CellAntigenRecognition

a

CD40

LFA-1

(CD11a/18)

LFA-3

(CD58)

Antigen-presenting cell or B cell

MHC

class II

molecule

(CD80)B-7

V-CAM (CD1LFA1a/1-18)

LFA-3

(CD58)

MHC

class I

molecule

(CD80)B-7

CD4 4

VLA-4

(CD49/29)

(act.)

CD2

CD4

TCR–CD3

complex

CD40L CD28

(naive)

T helper cell (CD4+)

CD8

CD2

TCR–CD3

complex

Cytotoxic T cell (CD8+)

b

α 2 β 2

α 1

β 1

VαVβ

CαCβ

α 3 β 2 M

Vα Vβ

Cα Cβ

α 1

α 2

IC(CAM-1D 54 )

ICAM-1

(CD 54 )

S

Antigen-presenting cell or target cell

CD4 4

CD28

(naive)

Fig.2. 9 aTheinteractionsofAPCsorBcellswithCD4+Tcells(Thelpercells)are

mediatedbyMHCclassIImolecules(heterodimers).bInteractionsbetweenCD8+

Tcells(cytotoxicTcells)andtheirtargetcellsaremediatedbyMHCclassImo-

lecules.Thepresentingpeptideisshowninviolet.“S”indicatesasuperantigen,

namedafteritscapacitytoactivatemanydifferentThelpercellsthroughitsability

tobindtotheconstantregionsofboththeMHCandTCRmolecules(naive=non-

activatedTcells,act.=activatedTcells).

2

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Kayser, Medical Microbiology © 2005 Thieme

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