THE TWO „ARMS” OF THE IMMUNE SYSTEM

THE TWO „ARMS” OF THE IMMUNE SYSTEM

• INNATE/NATURAL IMMUNITY

• ACQUIRED IMMUNITY

WHY IS THE IMMUNE SYSTEM SWHY IS THE IMMUNE SYSTEM SOO IMPORTANT? IMPORTANT?

VVirusesiruses

MMulticellular parazites ulticellular parazites (helminths)(helminths)

MMonocellular paonocellular parrazitesazites

VirusVirus

3 3 hourshours

3 3 hourshours

BacBacteriateria

PATHOGENS

Biomass: 90% microbes

Animal mass < 5 – 25x microbes

18 - 30 years

VARIABILITYVARIABILITYRapid evolutionRapid evolution

AdaptationAdaptationSelectionSelection

NATURAL/INNATE• Rapid, prompt

response (hours)• No variable receptors• No improvement

during the response• No memory• Not transferable• Can be exhausted,

saturated

CHARACTERISTICS OF INNATE IMMUNITY

ADAPTIVE/ACQUIRED• Time consuming (several

days)• Variable antigen receptors • Efficacy is improving

during the response• Memory• Can be transferred• Regulated, limited

COMMON EFFECTOR MECHANISMS FOR THE ELIMINATION OF PATHOGENS

CELLS

HUMORAL

FACTORS

Phagocytes (monocyte/macrophage, neutrophil, dendritic cell)

Killer cells (NK cell, δ T cell)

B1 lymphocytes (CD5+)

B lymphocytes (B2)

T lymphocytes

helper T cell

cytotoxic T cell

Enzymes (lysozyme, pepsin, trypsin)

Antibacterial peptides

Complement system

Cytokines, chemokines

Antibodies

TWO LINES OF IMMUNE DEFENSE

INNATE/NATURAL IMMUNITY

ACQUIRED/ADAPTIVE IMMUNITY

SENSINGSENSING

RECOGNITIONRECOGNITION

SIGNALINGSIGNALING

RESPONSERESPONSE

INNATE IMMUNITYINNATE IMMUNITY

CellsCells

ReceptorsReceptors

Signaling Signaling pathwayspathways

Cell-Cell Cell-Cell collaborationcollaboration

Effector Effector functionsfunctions

DEFENSE SYSTEMSDEFENSE SYSTEMS

ADAPTIVE IMMUNITYADAPTIVE IMMUNITY

SENSINGSENSING

RECOGNITIONRECOGNITION

SIGNALINGSIGNALING

RESPONSERESPONSE

SinusesTracheaLungs

BRONCHIAL TRACT EYES

Oral cavityesophagus

StomachIntestines

GASTROINTESTINAL SYSTEM

SKIN

PHYSICAL BARRIERS PROTECTING OUR BODY FROM

THE ENVIRONMENT

Damage

Infection

KidneyBladderVagina

UROGENITAL SYSTEMWALDEYER RINGTonsils, adenoids

Palatinal, pharyngeal lingual and tubar tonsils

EPITELIAL SURFACES ARE IMPORTANT IN THE FIRST LINE OF DEFENSE

α2-macroglobulin inhibits potentially damaging proteases

About 10% of serum proteins are protease inhibitors.

Human defensins are variable antimicrobial peptides

Peptides of 30-40 amino acids, amphipathic character They penetrate microbial membranesOngoing race between pathogens and the immune system of the host

Normal flora

Cells of human body: 90% microbes, 10% human

Symbiotic, non-pathogenic microbes– mucosal membrane, skinBacteria, Fungi, Protozoa Gut – colonalization after birth1012 bakteria/g (1.5 kg) intestinal content1000 species100-times more bacterial genes then eukaryotic

„peaceful” commensalismsvitamins (i.e. K1 vitamin)real ecosystem, survival of the fittest,

competition with pathogenic organismthe few who brake in through the gut

epithelium induce local immune responseImportant role in:

- development of mucosal and systemic immunity- normal development of peripheral lymphoid organs- maintenance of basic level of immunity

RECOGNITION

BY THE INNATE IMMUNE SYSTEM

INNATE/NATURAL IMMUNITY

RECOGNITION

Richard Pfeiffer, a student of Robert Koch – ENDOTOXIN ENDOTOXIN There must be a receptor that recognizes endotoxinLipopolysaccharide (LPS) receptor remained elusive

The Dorsoventral Regulatory Gene Cassette Spätzle/Toll/Cactus controls the potent antifungal response in Drosophila adultsBruno Lemaitre, A Hoffmann et al, Cell, 1996

Spätzle: Toll ligand

Toll: Receptor

Cactus: I-kB

Dorsal: NF-kB

Drosomycin

BaBacctteeriumrium

CD14CD14TLR4TLR4

LPSLPS

NFkBNFkBMyD88MyD88

IRAKIRAK

LPBLPB

IL-6IL-6

FungusFungus

TollToll

CCaacctustusTubeTube

SpätzelSpätzel

PeptidPeptid

ProteaseProtease

PellePelleRelRelishish

TOLL RECEPTORS ACTIVATE PHYLOGENETICALLY CONSERVED SIGNAL TRANSDUCTION PATHWAYS

InflammationAcute phase responseDanger signal

MacrophageDrosophila

IL-1R associated Kinase

WHAT IS RECOGNIZED BY INNWHAT IS RECOGNIZED BY INNAATE AND ACQUIRED TE AND ACQUIRED IMMUNITY?IMMUNITY?

Common pattern of groups of pathogensCommon pattern of groups of pathogensPathogen Associated Molecular PatternPathogen Associated Molecular Pattern

PAMPPAMPRecognition by receptorsRecognition by receptors

Pattern Recognition ReceptorPattern Recognition ReceptorPRRPRR

9-19-133 various various Toll-Toll-rreecceptoreptorssTLR familyTLR family

SSeveral millions antigen receptorseveral millions antigen receptors

UUnique structural elenique structural elemmentsentsAntigenic determinantAntigenic determinant

Recognition by highly speciRecognition by highly speciffic ic aantigen receptorsntigen receptors

B cell receptorB cell receptor BCR (sIg) BCR (sIg)T cell receptorT cell receptor TCR TCR

RECEPTORS

InInnate immunitynate immunity

AncientAncient 450 450 million yearsmillion years

AAcquired immunitycquired immunity

MaMaccrorophage/Dendritic cellphage/Dendritic cell

TLR5TLR5

FlageFlagelllinlin

VViirusrus

TLR3TLR3

ddssRNARNA

TOLL RECEPTORS RECOGNIZE VARIOUS MICROBIAL STRUCTURES

TLR2TLR2

PeptidoglycanePeptidoglycane

Gram+

TLR4TLR4

LPSLPS

TLR6TLR6

Gram-

InterferonInterferonproducing cellproducing cellpDpDCC

IFN

BaBacctteeririaa

CpG DNACpG DNA

TLR9TLR9TLR7TLR7TLR8TLR8

ssRNSssRNS

ALL STRUCTURES ARE ESSENTIAL FOR THE SURVIVAL OR REPLICATION OF THE PATHOGEN

TTLRLR

CONSERVED RECEPTORS/SENSORS THAT DETECT DANGER SIGNALSCONSERVED RECEPTORS/SENSORS THAT DETECT DANGER SIGNALS

MEMBRANEMEMBRANE

TLR3TLR3 FibroblastFibroblastEpithelial cellEpithelial cellDCDC

CELL MEMBRANEBacteriaBacteria

MEMBRANES OF

INTRACELLULAR VESICLESvirus

LRR

TIRdomain

TIR: Toll-Interleukin Receptor signaling domain

PHAGOCYTES ARE ABLE TO RECOGNIZE PATHOGENSPHAGOCYTES ARE ABLE TO RECOGNIZE PATHOGENS

Toll receptor-mediated signaling

Toll receptor

PHAGOCYTES (macrophages, dendritic cells, neutrophil granulocytes) PHAGOCYTES (macrophages, dendritic cells, neutrophil granulocytes) RECOGNIZE PATHOGENS BY PATTERN RECOGNITION RECEPTORS RECOGNIZE PATHOGENS BY PATTERN RECOGNITION RECEPTORS

RECOGNITION IS ESSENTIALRECOGNITION IS ESSENTIAL

FcR, CR

RECOGNITION

CYTOPLASMIC SENSORSCYTOPLASMIC SENSORS

VESZÉLYT ÉRZÉKELŐ KONZERVÁLT RECEPTOROKVESZÉLYT ÉRZÉKELŐ KONZERVÁLT RECEPTOROK

NLR: NOD-like receptorRLR: RIG-like receptor

TLR

CYTOPLASMCYTOPLASM

CARD-CARD-helicase

RLH

CONSERVED RECEPTORS SENSING DANGER SIGNALSCONSERVED RECEPTORS SENSING DANGER SIGNALSNLR nod-like receptors

Leucin rich repeatsLeucin rich repeatsNucleotide binding domain

NLRP1 – ASCNLRP1 – ASCNLRP3 – ASC – CARDINALNLRP3 – ASC – CARDINAL

NBDNBDNN CC

PYRPYR

CARDCARD

NOD1/2, IPAF/NLRC4NOD1/2, IPAF/NLRC4

MEMBRANMEMBRAN

TLR3TLR3

BIRBIRIPAFIPAF

FibroblastFibroblastEpithelial cellEpithelial cellDCDC

NBDNBD

NBDNBD

Conventional DC Plasmacytoid DC

5

887733 7 10

99

NLR=NOD/NALP (IL-1NLR=NOD/NALP (IL-1ββ))RLH=RIG-1/MDA5 (IFN)RLH=RIG-1/MDA5 (IFN)

NLRNLR

IL-1βIL-12/23

IL-10

Th1/Th17/Th2

IFNαβ

NK/DC

1

24 6

16

RLHRLHRLHRLH

DANGER SIGNALS ARE TRANSLATED TO CYTOKINE SECRETION DANGER SIGNALS ARE TRANSLATED TO CYTOKINE SECRETION THROUGH VARIOUS MOLECULAR SENSORS IN DC SUBTYPESTHROUGH VARIOUS MOLECULAR SENSORS IN DC SUBTYPES

TLR1 – bacterial lipoprotein (together with TLR2)TLR2 – bacterial lipoprotein, peptidoglycane, lipoteicholic acid

(heteromer with TLR1 and TLR6)TLR3 – viral dsRNS, polyI:CTLR4 – bacterial LPSTLR5 – bacterial flagellinTLR6 – bacterial lipoprotein (with TLR2)TLR7 – viral ssRNATLR8 – GU rich viral ssRNS, imidazoquinolin (antiviral drug)TLR9 – unmethylated CpG DNATLR10 – modified viral nucleotides

SIGNALING

IN INNATE IMMUNITY

BaBacctteeriumrium

CD14CD14TLR4TLR4

LPSLPS

NFkBNFkBMyD88MyD88

IRAKIRAK

LPBLPB

IL-6IL-6

FungusFungus

TollToll

CCaacctustusTubeTube

SpätzelSpätzel

PeptidPeptid

ProteaseProtease

PellePelleRelRelishish

TOLL RECEPTORS ACTIVATE PHYLOGENETICALLY CONSERVED SIGNAL TRANSDUCTION PATHWAYS

InflammationAcute phase responseDanger signal

MacrophageDrosophila

IL-1R associated Kinase

Figure 3 The 'hourglass' shape of the innate immune response. Although microbial stimuli are chemically complex and although the innate immune response ultimately involves the activation of thousands of host genes, innate immune signals traverse a channel of low complexity. Ten Toll-like receptors (TLRs), four TIR (Toll/interleukin-1 receptor homologous region) adaptors and two protein kinases are required for most microbial perception. This circumstance lends itself to effective pharmacotherapeutic intervention. NF-B, nuclear factor-B; STAT1, signal transducer and activator of transcription 1.

TOLL RECEPTOR MEDIATED SIGNALLING

NEW THERAPEUTIC TARGET

EFFECTOR MECHANISMS OF INNATE IMMUNITY

Bacterium

Complement proteins Lysis of bacteria

Inflammation

Complement-dependent phagocytosis

COMPLEMENT

PhagocytosisIntracellular killing

PHAGOCYTOSIS Phagocyte

Bacterium

CELLULAR AND HUMORAL MECHANISMS OF INNATE IMMUNITY

INFLAMMATION

BacteriumLPS

Cytokines Neutrophil

NK-cell

Macrophage

TNF

IL-12

IFN

NK-CELLSVirus-infected

cell

NK-cell Lysis of infected cell

DegradationACTIVATION

Uptake

PHAGOCYTOSIS

MECHANISMS OF INNATE IMMUNITY

Phagocyte

PRR

0.5 - 1 hours

The amount of internalized particles is limited Antigen + Antibody

ACQUIRED IMMUNITY

Bacterium

Intracellular killing

Antigen presentationT cell

ACQUIRED IMMUNITY

PHAGOCYTE SYSTEMPHAGOCYTE SYSTEM

NEUTROPHIL GRANULOCYTENEUTROPHIL GRANULOCYTEMONOCYTE – MACROPHAGE – DENDRITIC CELLMONOCYTE – MACROPHAGE – DENDRITIC CELL

Defence against infectiousdiseasesElimination of tumor cells

Gatekeeper functionSensing commensals and pathogensRapid activation of innate immunityPriming adaptive immune responsesMaintenance of self tolerance

Macrophages ingest and degrade particulate antigens through the use of long Macrophages ingest and degrade particulate antigens through the use of long pseudopodia that bind and engulf bacteria. The engulfed bacteria are degraded pseudopodia that bind and engulf bacteria. The engulfed bacteria are degraded when the phagosome fuses with a vesicle containing proteolytic enzymes when the phagosome fuses with a vesicle containing proteolytic enzymes (lysosome), forming the phagolysosome. Specialized compartments also exist in (lysosome), forming the phagolysosome. Specialized compartments also exist in the macrophage to promote antigen processing for presentation to antigen-the macrophage to promote antigen processing for presentation to antigen-specific T cells.specific T cells.

PHAGOCYTOSIS

Opsonization enhances the efficiency of phagocytosis of pathogens by phagocytes

Killing of bacteria by neutrophils: azurophilic and specific granules

azurofil ic specific granulsLyzozyme NADPH oxidaseDefensins LyzozymeMieloperoxidaseCathepsin Gelastase

Phagocyte oxidase (Phox) produces reactive oxidative species (ROS) that help destroy pathogens

Failure of phagocytes to produce reactive oxigen speciesin chronic granulomatous didease

PROTECTIONPROTECTION

against against bacteriabacteria and and fungifungi is down is down

regulatedregulated

NK-cellIL-12

macrophageIFNcytokines

neutrophilTNF-

INFLAMMATION – ACUTE PHASE RESPONSE

hrs

Pla

sma

leve

l

1 2 3 4 5

LPS (endotoxin) (Gram(-) bacteria)

TNF-

IL-1IL-6

Kinetics of the release of pro-inflammatory citokines in bacterial

infection

TNF-IL-1IL-6

Few hours

ACUTE PHASE RESPONSE

Bacterium

LPS

DANGER SIGNAL

ACTIVATION

PRR

MECHANISMS OF INNATE IMMUNITY

INFLAMMATORY RESPONSE INFLAMMATORY RESPONSE

The classic symptoms of inflammation:

redness (rubor) - vasodilation, swelling (tumor) - edema, heat (calor) – increased perfusion, pain (dolor) – factors stimulating nociceptors,

loss of function (functio laesa)

CONSEQUENCECONSEQUENCESS OF OF MACROPHAGE AMACROPHAGE ACTIVATIONCTIVATIONSYNTHESIS OF SYNTHESIS OF CCYTOKINESYTOKINES

Systemic effects of pro-inflammatory cytokines

Systemic release of TNFa initiates septic shock

Septic shockLocal production of TNFα (and IL1) is beneficial, and protective, BUT systemic releasemay cause deathDrop in blood volume and hence blood pressure Disseminated intrvascular coagulation

Pro-inflammatory cytokines activate endothel which recruits immunocytes from blood to infected tissues (extravasatio)

Liver

C-reactive proteinPhosphocolin

binding (e.g.fungi)COMPLEMENT

Serum Amyloid Protein (SAP)

Mannose/galactose binding

Fibrinogen

Mannose binding lectin/protein

MBL/MBPCOMPLEMENT

IL- 6

THE ACUTE PHASE RESPONSE

IL-6 induces the production of acute phase protiens

Phosphocoline bindingFungi, bacterialCell wall.

Lysis of bacteria

COMPLEMENT ACTIVATION

InflammationChemotaxis

Complement-dependent phagocytosis

Bacterium

COMPLEMENT

Lectin pathwayAlternative

pathway

Antigen + Antibody

ACQUIRED IMMUNITY

Complement-proteins

Few minutes – 1 hour

Enzymes get fragmented, complement activity can be exhausted

MECHANISMS OF INNATE IMMUNITY

RECOGNITION BY SOLUBLE RECOGNITION BY SOLUBLE MOLECULESMOLECULES

MANNOSE BINDING LECTINMANNOSE BINDING LECTIN

EEukariotic cellsukariotic cells

GluGluccooseseaminamin

MannMannoseose

GalaGalactosectose

NeuraminNeuraminic acidic acid

GLYCOSYLATION OF PROTEINS IS DIFFERENT IN VARIOUS SPECIES

MannoseMannose

ProkarProkariotic cellsiotic cells

PATTERN RECOGNITION BY MANNAN BINDING LECTINPATTERN RECOGNITION BY MANNAN BINDING LECTIN

Strong binding No binding

BaBacteriumcterium

lysis

Complementactivation

MacrophagePhagocytosis

CR3

LECTIN PATHWAY

NK cells

Type I IFNs increase their cytotoxicity (100x)

IL12, and TNFα are also able to activate them

IFNγ production --- MF, DC activation

- 5-10% of lymphocytes in circulation- bigger than T or B lymphocytes - several granules in their cytoplasm- have no antigen binding receptors („null cells”)- participants of native immunity