Medical Microbiology

ornoprotection.Instead,immunologicalprotectionrequiresantigen-depen-
dentactivationofBandTcells,whichthenproduceantibodiescontinuously
orcanrapidlymediateeffectorTfunctionsandcanrapidlymigrateintoper-
ipheraltissuestocontrolvirusinfections.
Usuallythesecondtimeahostencountersthesameantigenitsimmune
responseisbothacceleratedandaugmented.Thissecondaryimmunere-
sponseiscertainlydifferentfromtheprimaryresponse,however,itisstill
amatterofdebateastowhethertheseparametersalonecorrelatewithim-
muneprotection.Itisnotyetclearwhetherthedifferencebetweenaprimary
andsecondaryimmuneresponseresultssolelyfromtheincreasednumbers
ofantigen-specificBandTcellsandtheiracquisitionof“memoryqualities”,
orwhetherimmuneprotectionissimplyduetocontinuousantigen-induced
activation(Table2. 8 ).

ImmunologicalMemory 95

Table2. 8 CharacteristicsofT-andB-CellMemory

MemoryTcells MemoryBcells

Resting Activated Resting Activated

Localization
andmigration

Blood,spleen,

lymphnodes

Blood,spleen,

lymphnodes,

andsolid

tissues

Blood,spleen,

lymphnodes

Germinalcenters

inlocallymph

nodes,bone

marrow

Function Secondary
T-cellresponse

Immediate

targetcell

lysisand

interleukin

release

Secondary

B-cellresponse

SustainedIgG

response

Timelapse
toprotective
response

Slow Fast Slow Immediate

Proliferation
andlocation
ofproliferation

Insecondary

lymphoid

organs

Onlyin

secondary

lymphoid

organswith

antigen

residues

Blood,spleen Germinalcenters

withantigen-IgG

complexes

Antigen
dependence

No Yes No Yes

2

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Kayser, Medical Microbiology © 2005 Thieme

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