RECOGNITION

BY THE INNATE IMMUNE SYSTEM

FUNCTIONAL ATTRIBUTES OF INNATE AND ADAPTIVE IMMUNITYFUNCTIONAL ATTRIBUTES OF INNATE AND ADAPTIVE IMMUNITY

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

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

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

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 ESSENTIALMacrophage, dendritic cell – ACT AS Macrophage, dendritic cell – ACT AS TISSUE SENSORS (GATE KEEPERS) TISSUE SENSORS (GATE KEEPERS) Neutrophil granulocytes – MIGRATE FROM THE BLOOD TO THE SITE OF Neutrophil granulocytes – MIGRATE FROM THE BLOOD TO THE SITE OF

INFLAMMATIONINFLAMMATION

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 is not synthesized

SIGNALING

IN INNATE IMMUNITY

Sensing of LPS by TLR4 leads to activation of the Transcription factor NFkB and the synthesis of

inflammatory cytokines.

TLR4 activation can lead to the production of either inflammatory

cytokines or (antiviral) type I interferons.

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

Activation of macrophages induces secretion of multiple pro-inflammatory cytokines

Systemic release of TNFa initiates septic shock

Septic shockLocal production of A TNFα (and IL1) is beneficial,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)

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

Phsgocyte 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

RECOGNITION BY SOLUBLE RECOGNITION BY SOLUBLE MOLECULESMOLECULES

MANNOSE BINDING LECTINMANNOSE BINDING LECTIN

EEukariotic cellsukariotic cells

GluGluccooseseaminamin

MannMannoseose

GalaGalactosectose

NeuraminNeuraminidaseidase

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

Liver

C-reactive proteinPhosphocolin

binding (e.g.fungi)COMPLEMENT

Serum Amyloid Protein (SAP)

Mannose/galactose binding

Chromatin, DNA, Influenza

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.

RECOGNITION

CYTOPLASMIC SENSORSCYTOPLASMIC SENSORS

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

NOD-like receptors

Group of abot 20 proteins named after NOD1 and NOD2

NOD family: --- intracellular bacteriaActivate NF-kB and induce chemokine secretion

NALP family regulation of cytokine release mainly IL1, 18, 33,produced in an inactive form. (via regulation of caspases)With other adaptor proteins they form „Inflammosomes”Activation: by various bacterial pore forming toxins

endogenous compounds, mono sodium urate (MSU), Ca pyrophosphate dihydrate (CPPD), ATP

INTERFERON RESPONSEINTERFERON RESPONSE

EFFECTS OF TYPE I INTERFERONS

Plasmacytoid dendritic cells produce 1000x more type I interferon than other cells

NATURAL INTERFERON PRODUCING CELLS – IPC

After viral infection they are accumulated at the T cell zone of the lymph nodes

vírus

paracrine

autocrine

Infected cell

subtypes

IFN-

IFN-

IFN response

IRF-3

IRF-7

Virus

IFN-

IFN-

NFBAP-1

Type I IFN receptor

IFN response

VIRUS INDUCED TYPE I INTERFERON PRODUCTION

IRF: interferon regulatory factor

IRF-3

Plasma membrane

Cytoplasm

Type I. IFN receptor Type II. IFN receptorType III. IFN receptor (IFNλ)

TYK2 JAK1TYK2 JAK1

JAK2

JAK1JAK1

JAK2

STAT1STAT1

STAT2

Nucleus

STAT1 STAT2P

P

STAT1 STAT2P

P

STAT1STAT1 PP

STAT1STAT1 PP

IRF9

ISREISRE GAS – promoter elementsGAS – promoter elements

Antiviral immunity Antimycobacterial immunity

ISG15, Mx,OAS and

PKR

IL-10R2IFNLR1IFNAR1/2 IFNG1/2

Interferon-stimulated genes

Interferon-stimulated Regulatory elements

ISGF-3

GAS: Gamma Activating sequence

Signal Transducers and Activators of Transcription

INTERFERON EFFECTOR PATHWAYSinduction of the „antiviral state

• 1. Mx GTPase pathway– Trap viral particles in Endoplasmic Reticulum

• 2. 2',5'-oligoadenylate-synthetase (OAS)-directed Ribonuclease L pathway– degrade viral RNA

• 3. Protein kinase R (PKR) pathway (Ser/Thr kinase, dsRNA-dependent)– inhibit translation

• 4. ISG15 ubiquitin-like pathway– modify protein function

CONTROL ALL STEPS OF VIRAL REPLICATION

Oligomer accumulationin cytoplasmic

membranes(e.g. ER)

(Nucleus)

(Cytoplasm)

ISRE MxA

MxA monomer

MxA oligomer

Trapped viralcomponents

(Nucleus)

(Cytoplasm)

ISRE OAS1

Inactive OAS1 monomer

Induction byviral dsRNA

Active OAS1 tetramer

synthetized pppA(2’p5’A)ninactive

RNaseLmonomer

active RNaseLdimer

cleaved RNA

(Nucleus)

(Cytoplasm)

ISRE PKR

Inactive PKR monomer

Active PKR dimer

Induction byviral RNAs

EIF2 EIF2P Inhibition of

translation

Mechanism of action of Mechanism of action of MxA, OAS1 and PKRMxA, OAS1 and PKR