2. sw_antigen and protein in of microbes

7/29/2019 2. Sw_antigen and Protein in of Microbes

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Inductionofinnateandadaptive

immunitybymicrobial

componen

S.Wahyuni,MD,PhDDepartmentofParasitology,

MedicalFaculty,HasanuddinUniversity

[email protected]

+628152531325

DURINGLECTURE/DISCUSSION

29/07/09 S.Wahyuni/BMD 2

MicrobialPathogen

grampositive/negativebacteria

mycobacteria

fungi

protozoa helminth


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Antigenofbacteria

Structureofbacteria

Antigenofviral

3componentof

viral

Capsid Protein

Genome DNAor

RNA

Envelope (notall

viruses)


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Structureofprotozoaandhelminth

Antigenofmicrobes

Theinnateimmunesystemrecognizesmolecularstructures

thatarecharacteristicofmicrobialpathogensbutnot

mammaliancells.

Themicrobialsubstancesthatstimulateinnateimmunity

are called atho enassociated molecular atterns

(PAMPs).

Differentclassesofmicrobes(e.g.,viruses,gramnegative

bacteria,grampositivebacteria,fungi)expressdifferent

PAMPs.

Innate Immunity Adaptive Immunity

Specificity For structures shared by classes of

microbes (pathogen-associated

molecular patterns)

For structural detail of microbial molecules

(antigens); may recognize nonmicrobial

antigens

Receptors Encoded in germline; limited diversity

(pattern recognition receptors)

Encoded by genes produced by somatic

recombination of gene segments; greater;

diversity

Distribution

of receptors

Nonclonal: identical receptors on all

cells of the same lineage

Clonal: clones of lymphocytes with distinct

specificities express different receptors

Discriminati-

on of self and

non-self

Yes; healthy host cells are not

recognized or they may express

molecules that prevent innate immune

reactions

Yes; based on elimination or inactivation of

self-reactive lymphocytes; may be imperfec


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Theinnateimmunesystemrecognizesmicrobialproductsthatareoftenessentialforsurvivalofthemicrobes.

Pathogen-Associated Molecular Patterns Microbe Type

Nucleic acids ssRNA Virus

dsRNA Virus

CpG Virus, bacteria

Proteins Pilin Bacteria

Flagellin Bacteria

Cell wall lipids LPS Gram-negative bacteria

Lipoteichoic acid Gram-positive bacteria

Carbohydrates Mannan Fungi, bacteria

Dectin glucans Fungi

TorecognizePAMPsinnateimmunesystem

uses

severaltypesofcellularreceptors,presentin

different locations in cells

solublemoleculesreceptorsinthebloodand

mucosalsecretions

Cellularlocationsofpatternrecognitionmoleculesoftheinnateimmunesystem


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Cell-Associated Pattern

Recognition Receptors Location

Specific

Examples PAMP/DAMP Ligands

Plasma membrane and

endosomal membranes

of dendritic cells,

phagocytes, B cells

endothelial cells, and

many other cell types

TLRs 1-9 Various microbial

molecules including

bacterial LPS and

peptidoglycans, viral

nucleic acids

C to lasm of NOD1/2 Bacterial cell wall

phagocytes epithelial

cells, and other cells

NALP family

(inflammaso

mes)

peptidoglycans

Flagellin, muramyl

dipeptide, LPS; urate

crystals; products of

damaged cells

RIG-like

receptors (RLRs)

Cytoplasm of

phagocytes and other

cells

RIG-1,

MDA-5

Viral RNA

Cell-Associated Pattern

Recognition Receptors Location

Specific

Examples PAMP/DAMP Ligands

C-type lectin-like

receptors

Plasma membranes

of phagocytes

Mannose

receptor

Microbial surface

carbohydrates with

terminal mannose and

fructose

Dectin Glucans present

in fungal cell

walls

Plasma membranes

of phagocytes

CD36 Mi crobi al di ac yl gl ycer ide s

N-Formyl

met-leu-phe

receptors

Plasma membranes

of phagocytes

FPR and FPRL1Peptides containing N-

formylmethionyl residues

Soluble Recognition

Molecules

Location Specific ExamplesPAMP Ligands

Pentraxins Plasma C-reactive protein Microbial

phosphorylcholine and

phosphatidylethanolamine

Collectins Plasma Mannose-binding

lectin

Carbohydrates with terminal

mannose and fructose

Alveoli Surfactant proteins

SP-A and SP-D

Various microbial structures

Ficolins Plasma Ficoli N-Acet l lucosamine and

lipoteichoicacidcomponents of the cell walls

of gram-positive bacteria

Complement Plasma C3 Microbial surfaces

Natural

antibodies

Plasma IgM Phosphorylcholine on

bacterial membranes and

apoptotic cell membranes


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CELLASSOCIATEDPATTERN

IMMUNITY

TolllikeReceptors

Familyofpatternrecognitionreceptorsexpressed

onmanycelltypes

Recognizeproductsofawidevarietyofmicrobes.

,

Responsestoawidevarietyofmoleculesthatare

expressedbymicrobialonly.

Alsoinvolvedinresponsetoendogenous

moleculeswhoseexpressionorlocationindicates

celldamage.

TLRsarefoundonthecellsurfaceandonintracellular

membranesandarethusabletorecognizemicrobesin

differentcellularlocations

TLRs1,2,4,5,and6areexpressedontheplasma

membrane where the reco nize various PAMPs in the,

extracellularenvironment.

TLRs3,7,8,and9aremainlyexpressedinsidecellson

endoplasmicreticulumandendosomalmembranes,where

theydetectseveraldifferentnucleicacidligandsfrom

foreignororunhealthyself


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Structure,location,andspecificitiesofmammalianTLRs

TLRrecognitionofmicrobialligands resultsintheactivationof

severalsignalingpathwaysandultimatelytranscription

factors,whichinducetheexpressionofgeneswhoseproducts

areimportantforinflammatory andantiviralresponses

The ma or transcri tion factors that are activated b TLR

signalingpathwaysare:

Nuclearfactor B (NFB)

Protein1(AP1)

Interferonresponsefactor3(IRF3)andIRF7

SignalingfunctionsofTLRs


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NODlikeReceptors(NLR)

Acytosolic ReceptorsforPAMPs thatfunction to detectinfectionorcell

damageinthecytoplasm

Afamily>20differentcytosolic proteins

Sensecytoplasmic PAMPsandrecruitotherproteinstoformsignaling

complexes thatpromoteinflammation.

NLRproteinscontainatleastthreedifferentdomainswithdistinct

structuresandfunctions.

TherearethreeNLRsubfamiliescalledCARD,Pyrin,andBIRdomains.

NLRsarefoundinawidevarietyofcelltypes

Theinflammasome

RIGlikeReceptors(RLR)

Acytosolic ReceptorsforPAMPs thatfunctiontodetect

infectionorcelldamageinthecytoplasm

Arecytosolic sensorsofviralRNAthatrespondtoviralnucleic

acidsbyinducingtheproductionoftheantiviraltypeI

interferons.

CanrecognizedoublestrandedandsinglestrandedRNA,

includesthegenomesofRNAvirusesandRNAtranscriptsofRNAandDNAviruses.

Areexpressedinawidevarietyofcelltypes,includingbone

marrowderivedleukocytesandvarioustissuecells.


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OtherCellAssociatedPatternRecognition

Receptors

Expressedontheplasmamembranesofvariouscelltypesandrecognizemicrobialmolecules

Someofthesereceptorstransmitactivatingsignals,similarto

TLRs,thatpromoteinflammatory responsesandenhance

.

Otherreceptorsmainlyparticipateintheuptakeofmicrobes

intophagocytes.

OtherCellAssociatedPatternRecognition

Receptors

Carbohydrate receptor facilitatethephagocytosis ofthemicrobesandstimulatesubsequentadaptiveimmuneresponses.

Mannosereceptor(CD206) isinvolvedinphagocytosis ofmicrobes

Dectins dendritic cellassociatedCtypelectin)

Langerin(CD207)mainlyexpressedbyepidermalLangerhanscells

DCSIGN recognizeandbindHIV1gp120envelopeglycoprotein

Scavengerreceptors(CD36) recognizecellsurfaceprotein(LPS,lipoteichoicacid,nucleicacids, glucan,andproteins)andmediatingtheuptakeofoxidizedlipoproteinsintocells.

NFormyl metleuphe receptors expressedbyneutrophilsandmacrophages,respectively,recognizebacterialpeptidescontainingNformylmethionylresiduesandstimulatedirectedmovementofthecells.

CELLULARCOMPONENTSOFTHE


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Epithelialcell Phagocytes

Dendritic Cells

NKcells

Tcells:invariantnaturalkillerTcells(iNKT),

Tcells,intraepithelialTcellswith TCR

Bcell: B1BcellsandmarginalzoneBcells.

MastCells

Epithel

Interfacesbetweentheenvironmentandthemammalianhost(skinandmucosalsurfacesofthegastrointestinal,respiratory,andgenitourinarytracts)

. Keratin blockmicrobialpenetrationintodeeper

layersoftheepidermis.

Mucus impairsmicrobialinvasionandfacilitatesmicroberemoval

Leukocytesproducepeptides(defensins andthecathelicidins)thathaveantimicrobialproperties.

EpithelialBarriers


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Phagocytes

Macrophagesandneutrophils,arethefirstlineofdefenseagainst

microbesthatbreachepithelialbarriers

2generaltypesoffunctions

Internalizeandkillmicrobes

Producingvariouscytokinesthatpromoteinflammationandalso

enhancetheantimicrobialfunctionofhostcellsatthesiteofinfection.

Dendritic Cells

Presentinepitheliaandmosttissuesofthebody.

Arepoisedtodetectinvadingmicrobes. Ableto:

takeupmicrobialproteinantigens

transportthemtolymphnodeswherenaiveTcellshome

alteranddisplaytheproteinantigensinawaythattheTcellscanrecognize.

Plasmacytoid dendritic cells(morphologyissimilartoantibodyproducingplasmacells)isthemajorsourceofantiviralcytokines,typeIinterferons,producedinresponsetoviralinfections.

Distinguishinfectedandstressedcellsfromhealthycells

NKcellactivationisregulatedbyabalancebetweensignalsthataregeneratedfrom

NKcells

activatingreceptorsandinhibitoryreceptors. Activatingreceptorsrecognizeligands oninfected

andinjuredcells

Inhibitoryreceptors:signalsthatpromoteorinhibitNKresponsesandrecognizehealthynormalcells.


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FunctionsofactivatingandinhibitoryreceptorsofNKcells

TandBLymphocyteswithLimitedAntigen

ReceptorSpecificities

CertainsubsetsofTandBlymphocyteshave

verylittlereceptordiversity

Thesesubsetsrecognizestructuresexpressed

microbialspecies(PAMPs)

Tcells:invariantnaturalkillerTcells(iNKT), T

cells,intraepithelialTcellswith TCRs

Bcell: B1BcellsandmarginalzoneBcells.

MastCells

Presentintheskinandmucosalepithelium

Rapidlysecreteproinflammatory cytokinesandlipidmediatorsinresponsetoinfectionsandotherstimuli.

Havecytoplasmic granulescontainingvariousinflammatorymediatorsthatarereleasedwhenthecellsareactivated

Vasoactive amines(suchashistamine)thatcausevasodilation andincreasedcapillarypermeability,

Poteolytic enzymesthatcankillbacteriaorinactivatemicrobialtoxins.

Synthesizeandsecretelipidmediators(suchasprostaglandins)andcytokines(suchasTNF).

Usuallylocatedadjacenttobloodvesselstheirreleasedgranulecontentsrapidlyinducechangesinthebloodvesselsthatpromoteacuteinflammation.

Providedefenseagainsthelminths andareresponsibleforsymptomsofallergicdiseases.


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SOLUBLERECOGNITIONAND

EFFECTORMOLECULESOFINNATE

IMMUNITY

Naturalantibody

TheComplementSystem

Pentraxins

Collectins andFicolins

Recognizemicrobesandpromoteinnateresponsesexistinsolubleforminthebloodandextracellularfluids.

Thesolubleeffector moleculesfunctionintwomajorways. bindtomicrobes,actasopsonins andenhancetheabilityof

macrophages,neutrophils,anddendritic cellstophagocytosethe microbes.

promoteinflammatoryresponsesthatbringmorephagocytestositesofinfections,andtheymayalsodirectlykillmicrobes.

Sometimescalledthehumoral branchofinnateimmunity

Include:naturalantibodies,thecomplementsystem,collectins,pentraxins,andficolins


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NaturalAntibodies

SubsetsofBcellsthatproduceantibodieswithonlyalimitednumberofspecificitieswithoutovertexposuretoforeignantigens

Alreadypresentbeforeinfections,andtheyrecognizecommonmolecularpatternsonmicrobesorstressedanddyingcells.

Usuallyspecificforcarbohydrateorlipidmoleculesbutnotproteins,andmostareIgM antibodies

Provideprotectionagainstbacterialinfectionsandfacilitatethephagocytosis ofapoptoticcells.

TheantiABObloodgroupantibodies,anotherexampleofnaturalantibodies,recognizecertainglycolipids(bloodgroupantigens)expressedonthesurfaceofmanycelltypes,includingbloodcells.

TheComplementSystem

Severalplasmaproteinsthatworktogethertoopsonize

microbes,topromotetherecruitmentofphagocytestothe

siteofinfection,andinsomecasestodirectlykillthe

microbes

Com lement activation involves roteol tic cascades in ,

whichaninactiveprecursorenzyme,calledazymogen,is

alteredtobecomeanactiveproteasethatcleavesand

therebyinducestheproteolytic activityofthenext

complementproteininthecascade.

Asthecascadeproceeds,theenzymaticactivitiesresultin

tremendousamplificationoftheamountofproteolytic

productsthataregenerated

performtheeffector functions Has3pathways

Pathwaysofcomplementactivation


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Classicalpathway

SocalledbecauseitusesaplasmaproteincalledC1qtodetectantibodiesboundtothesurfaceofamicrobeorotherstructure

OnceC1qbindstotheFc portionoftheantibodies,twoassociatedserineproteases,calledC1randC1s,becomeactiveandinitiateaproteolytic cascadeinvolvingothercomplementproteins.

Oneofthemajoreffector mechanismsofthehumoral armofa apt ve mmuneresponses

BecauseIgM naturalantibodiesareveryefficientatbindingC1q,theclassicalpathwayalsoparticipatesininnateimmunity.

Solubleproteinscalledpentraxins,canalsobindC1qandinitiatetheclassicalpathway.

Alternativepathway

IstriggeredwhenacomplementproteincalledC3directlyrecognizescertainmicrobialsurfacestructures,suchasbacterialLPS.

C3isalsoconstitutivelyactivatedinsolutionatalowlevelandbindstocellsurfaces,butitistheninhibited

yregu atorymo ecu espresentonmamma ance s.

Becausemicrobeslacktheseregulatoryproteins,thespontaneousactivationcanbeamplifiedonmicrobialsurfaces.

Distinguishnormalselffromforeignmicrobesonthebasisofthepresenceorabsenceoftheregulatoryproteins.

Thelectinpathway

istriggeredbyaplasmaproteincalledmannosebindinglectin (MBL),whichrecognizesterminalmannoseresiduesonmicrobialglycoproteins andglycolipids,similartothemannosereceptoronphagocytemembranesdescribedearlier

MBL is a member of the collectin famil discussed later

withahexameric structuresimilartotheC1qcomponentofthecomplementsystem.

AfterMBLbindstomicrobes,twozymogenscalledMASP1(mannanbindinglectinassociatedserineprotease)andMASP2,withsimilarfunctionstoC1randC1s,associatewithMBLandinitiatedownstreamproteolytic stepsidenticaltotheclassicalpathway.


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mannosebindinglectin,andficolin

Pentraxins Isaphylogenetically oldgroupofstructurallyhomologous

pentameric proteins.

Prominentmembersofthisfamilyincludetheshort

pentraxins Creactiveprotein(CRP)andserumamyloid P(SAP)

andthelongpentraxin PTX3.

PTX3recogn zesvar ousmo ecu eson ung ,se ecte gram

positiveandgramnegativebacteria,andviruses.

CRP,SAP,andPTX3allactivatecomplementbybindingC1q

andinitiatingtheclassicalpathway.

Collectins

Areafamilyoftrimeric orhexameric proteins,

eachsubunitofwhichcontainsacollagenlike

tailconnectedbyaneckregiontoacalcium

.

Threemembersofthisfamily

Mannosebindinglectin (MBL)

PulmonarysurfactantproteinsSPA

PulmonarysurfactantproteinsSPD.


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Ficolins

plasmaproteinsthatarestructurallysimilartocollectins, possessingacollagenlikedomain,butinsteadofaCtype

lectin domain,theyhaveafibrinogentypecarbohydrate

recognitiondomain

ave eens ownto n severa spec eso acter a,

opsonizing themandactivatingcomplementinamanner

similartothatofMBL.

Themolecularligands oftheficolins includeN

acetylglucosamine andthelipoteichoic acidcomponentofthe

cellwallsofgrampositivebacteria.

THEINFLAMMATORYRESPONSE

Stepofinflammation

Releaseproinflammatory cytokinesbyresidentcellsinthe

tissue(mastcells,macrophages, andendothelial cells)in

responsetoPAMPorDAMP

Accumu at ono eu ocytes,p asmaprote ns,an u

derivedfromthebloodatanextravascular tissuesiteof

infectionorinjury

Phagocytosis andKillingofMicrobesbyActivated

Phagocytes


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C yt oki ne S iz e P rin ci pa l Ce ll Sou rce P rin ci pal Cel lu lar Target s an d Bi ologic Ef fec ts

Tumor necrosis

factor (TNF)

17 kD; 51-kD

homotrimer

Macrophages, T cells Endothelial cells: activation (inflammation,

coagulation)

Neutrophils: activationHypothalamus: fever

Liver: synthesis of acute-phase proteins

Muscle, fat: catabolism (cachexia)

Many cell types: apoptosis

Interleukin-1 (IL-1) 17-kD mature form;

33-kD precursors

Macrophages,

endothelial cells, some

Endothelial cells: activation (inflammation,

coagulation)

e pi thel ia l ce ll s Hypot ha la mus: f ever


Chemokines (see

Table 3-2)

8-12 kD Macrophages,

endothelial cells, T cells,

fibroblasts, platelets

Leukocytes: chemotaxis, activation; migration into

tissues

Interleukin-12 (IL-

12)

Heterodimer of 35-

kD and 40-kD

subunits

Macrophages, dendritic

cells

T cells: TH1 differentiation

NK cells and T cells: IFN- synthesis, increased

cytotoxic activity

Type I interferons

(IFN-, IFN-)

IFN-: 15-21 kD

IFN-: 20-25 kD

IFN-: macrophages

IFN-: fibroblasts

All cells: antiviral state, increased class I MHC

expression

NK cells: activation

Cytoki ne S iz e P ri nc ipal Ce ll Sourc e Pr inci pa l Cel lu la r Ta rg ets and Bi ol og ic Ef fe ct s

Interleukin-10

(IL-10)

Homodimer of 34-40

kD; 18-kD subunits

Macrophages, T cells

(mainly regulatory T

cells)

Macrophages, dendritic cells: inhibition of IL-12

production and expression of costimulators and class II

MHC molecules

Interleukin-6

(IL-6)

19-26 kD Macrophages,

endothelial cells, T

cells


B cells: proliferation of antibody-producing cells

Interleukin-15

(IL-15)

1 3 k D M acr op hag es , o th er s N K cell s: pr olif er ati on

T cells: proliferation (memory CD8+ cells)

Interleukin-18

(IL-18)

17 kD Macrophages NK cells and T cells: IFN- synthesis

Interleukin-23

(IL-23)

Heterodimer of

unique 19-kD subunit

and 40-kD subunit of

IL-12

Macrophages and

dendritic cells

T cells: maintenance of IL-17-producing T cells

Interleukin-27

(IL-27)

Heterodimer of 28-

kD and 13-kD

subunits

Macrophages and

dendritic cells

T cells: TH1 differentiation; inhibition of TH1 cells

NK cells: IFN- synthesis

Phagocytosisandintracellulardestructionofmicrobes


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THEANTIVIRALRESPONSE

Innateimmunesystemdealswithviral

infectionsistoinducetheexpressionoftypeI

interferons,whosemostimportantactionisto

.

ThetypeIinterferons aresecretedfrom

innatecellsandactonothercellstoprevent

spreadofviralinfection.

BiologicactionsoftypeIinterferons


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STIMULATIONOFADAPTIVE

IMMUNITY

Microbialcomponentthatinduceantibody

response theantigen

Componentofmicrobial(coats,capsules,

cellwalls,flagella,fimbrae,andtoxins)

thatcaninduceantibodyresponseis

calledantigen

Antigensareusuallyproteins or

polysaccharides ofmicrobial Lipids andnucleicacids areantigeniconly

whencombinedwithproteins and

polysaccharides.

Hapten: Smallforeignmoleculethatisnot

antigenic. Mustbecoupledtoacarrier

moleculetobeantigenic. Onceantibodiesare

formedtheywillrecognizehapten.


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Epitope: Smallpartofanantigenthatinteractswithan

antibody.

.

Eachepitope isrecognizedbyadifferentantibody.

MicrobialcomponentthatinduceTcells

response peptide

PeptideistheresultofantigenprocessingbyAPC

Peptidesareshortpolymers ofaminoacid

monomers linkedbypeptidebonds

Pe tides are distin uished from roteins on the basis

ofsize,typicallycontainingfewerthan50monomer

units.

PeptideshouldbedisplayedbyAPCtoactivateTcells

Readingmaterial

Abbas etal.InnateimmunityinCellular

Immunology2010ed

http://faculty.ccbcmd.edu/courses/bio141/lec

.

2. sw_antigen and protein in of microbes

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