Medical Microbiology

tiationmoleculesandregulationofcellsurfacemoleculeexpression).The

functionsofcytokinesareusuallypleiotropic,inthattheydisplayanumber

ofeffectsofthesame,orofadifferent,natureononeormorecelltypes.Below

isasummaryofcytokinefunctions:

&Promotionofinflammation:IL-1,IL-6,TNFa,chemokines(e.g.,IL-8).

&Inhibitionofinflammation:IL-10,TGFb.

&Promotionofhematopoiesis:GM-CSF,IL-3,G-CSF,M-CSF,IL-5,IL-7.

&ActivatingBcells:CD40L,IL-6,IL-3,IL-4.

&ActivatingTcells:IL-2,IL-4,IL-10,IL-13,IL-15.

&Anti-infectious:IFNa,IFNb,IFNc,TNFa.

&Anti-proliferative:IFNa,IFNb,TNFa,TGFb.

78 2 BasicPrinciplesofImmunology

CD4+THelperCellSubpopulations

andAPCsduringImmuneResponses

NK

cells

IFN-γ

IL-1 2

TH2

TH1

APC TH^0

Viruses

Bacteria

Viruses

Parasites

Allergens

Mast cells

Basophils

IL-4

–

Macrophages

Eosinophils

B cells

B cells

IFN-γ

IL-2

IL-4

IL-5

IL-1 0

IL-1 3

IgM

IgG2a

Delayed type

hypersensitivity

(DTH)

Defenses against

intracellular

microorganisms

IgG 1

IgE

+

+

Fig.2. 14 TH1andTH2cellsarederivedfromaTH0cell,andundergodifferentia-

tioninthepresenceofhelpderivedfromcytokines,DC,macrophages,andother

celltypes.TH1cellsareactivatedbyIL-1 2 andIFNcandinhibitedbyIL-4;whilstfor

TH2cellsthereverseistrue.Virusesandbacteria(particularlyintracellularbacter-

ia)caninduceaTH1responsebyactivatingnaturalkillercells.Incontrast,allergens

andparasitesinduceaTH2responseviathereleaseofIL-4.However,thestrongin-

vitrodifferentiationofCD4+TcellsintoTH1–TH2subsetsislikelytobelesssharply

definedinvivo.

2

Kayser, Medical Microbiology © 2005 Thieme