Primary lymphoid organs : - Bone marrow - Thymus Secondary lymphoid organs: - Spleen - Lymphatic...

Primary lymphoid organs:

- Bone marrow- Thymus

Secondary lymphoid organs:

- Spleen- Lymphatic vessels- Lymph nodes- Adenoids and tonsils- MALT (Mucosal Associated Lymphoid Tissue) GALT (Gut Associated Lymphoid Tissue) BALT (Bronchus Associated Lymphoid Tissue) SALT (Skin Associated Lymphoid Tissue)

NALT (Nasal Associated Lymphoid Tissue)

LYMPHOID ORGANS!!

THE TWO ARMS OF THE IMMUNE SYSTEMTHE TWO ARMS OF THE IMMUNE SYSTEM

Monocytes, Macrophages, Dendritic cells, Granulocytes, NK cells and Complement components

B and T cellsMonocytes, Macrophages, Dendritic cells, Granulocytes, NK cells and Complement components

!!

Professional phagocytic cellsmacrophagesneutrophyl granulocytesdendrtitic cells

the phagocytosed cells or molecules may modify the functions of the cell

phagocytosis followed by enzymatic degradation

Professional antigen presenting cellsmacrophagesB lymphocytesdendrtitic cells

they express MHCII molecules

the protein degradation products (peptides) can be presented to T lymphocytes by MHC molecules

!!

!!

Cells of innate immune system:

Macrophages:Macrophages are constitutively present in tissues and recognize microbes that enter these tissues and respond rapidly to these microbes. Initiate the immune response•These cells are phagocytes (eliminate the pathogens)•Activate the innate immune response (by secreted proteins, called cytokines)•Activate the adaptive immune system. Macrophages serve as APCs that display antigens to and activate T lymphocytes

•Dendritic cellsare constitutively present in tissues and recognize rapidly microbes that enter these tissues. Initiate the immune response.•They have phagocytic capabilities migrate to lymph nodes, and display microbial antigens to T lymphocytes,professional antigen presentimg cells (APC)

Neutrophil granulocytes

are phagocytes, the main function to eliminate the pathogens

Appear only in the circulation under normal condition

Main actors In inflammatory processes

!!

Infection

Phagocyte activation

How do immunocytes communicate:Soluble mediators

CYTOKINES & CHEMOKINESSoluble proteinsproduced by cells. They have strong effect on the function of other cells. Bit similar to hormones.

How do immunocytes communicate:Cell-cell interaction

Cell-cell communication takes place commonly in all the phases of the immune response

T

CTL

T

BY

Antibody productionActivation of accessory cellsDendritic cell macrophage

Antigen presentation

Target cell

Cell killing

The most important mediators of indirect cell communication in the immune system („hormones” of the immune system).

Act in low concentrations.

Cytokines can affect in an autocrine way, in a paracrine way, or in an endocrine way

pleiotropic effect.

Cytokines can act by synergistic or antagonistic ways to each other. A given cell may by affected by many cytokines resulting in the same effect redundant effect.

- The responsiveness of the given cell is based on the expression of cytokine-specific receptors.

THE MOST IMPORTANT FEATURES OF CYTOKINESTHE MOST IMPORTANT FEATURES OF CYTOKINES

!

Cytokines can be devided into sub-groups by origin and functional properties.

Functional groups:

Inflammatory cytokinesDirect the development and maturation of immune cellsDirect activation and differentiation of immune cells

hormons

cytokines

chemokine

interleukins

interferons

Categories of cytokinesCategories of cytokines

General schema of receptor funtion

MOLECULES OF THE IMMUNE SYSTEM

Most important receptors of the imune system

•receptors (BCR, TCR, MHCI, MHCII, PRR, etc.)

Soluble molecules:

• cytokines

• antibodies

• complement components

Receptors responsible for the recogniton of pathogens in the immune system

Caracteristics of innate immune system,macrophage, dendritic cells

PRR Pattern recognition receptors

Danger signal and Pathogen recognition mainly in the innate immun system

B cells BCR (B cell receptor) Antigen recognition of B cell

T cells TCR (T cell receptor) Antigen recognition of T cell

All nucleated cells in human

MHC (MHCI) Major Histocompatibility Complex

Do not recognise pathogens, but present intracellular peptides required for T cell receptor

professional antigen presenting cells:macrophages, DC, B cells

MHCII Do not recognise pathogens, but present extracellular peptides required for T cell receptor

INNATE IMMUNITY I

Physical and chemical barriers

pH of 3-4 Pepsin

Stomach

Skin

Tight junctions Keratin layer Antibacterial peptides; Defensins pH of 5.5 Fatty acids

Burns and susceptibility to infections!

pH of 3.8-4.5 Lactobacillus Lactic acid

Vagina

Eye Tear film (Oils, lactoferin, mucin and

lyzosyme)

Respiratory tract

Impaired cilia movement (CF)!

Cilliary movement Coughing, sneezing

Monocite / Monocite / macrofagmacrofag

e e DCDC Mast Mast

cellcellGranulo-Granulo-

citescites NK cellNK cell B cellB cell T cellT cell Comple-Comple-mentment

Recogni-tion

Cell-cel(APC)

Communication

Soluble

effector function

INNATE IMMUNITYPathogen recognition PRRs (TLRs, C type lectins, Mannose and Glucan binding lectins,

NLRs and RIG-I helicases)

Phagocytosis, effector functions

Communication/ Antigen presentation Intracellular – on surface MHC I complex proteins

Extracellular – on surface MHC II complex proteins

Recognition is inevitableRecognition is inevitable

Innate immunity as a first line of defence

Innate immune cells recognize frequently found structures of pathogens,

these are not found in human cells!

Examples: duple strain RNA bacterial cell wall components bacterial flagellin….

!!

Danger signal!The innate immune system also recognizes molecules that are released from damaged or necrotic cells. Such molecules are called damage-associated molecular patterns (DAMPs).

!!

Recognition is inevitableRecognition is inevitable

Innate immunity as a first line of defence

Innate immune cells recognize frequently found structures of pathogens,

these are not found in human cells!

Examples: duple strain RNA bacterial cell wall components bacterial flagellin….

!!

PAMPs- Pathogen associated molecular pattersStructures on pathogens recognized by the innate cells

PRR types

TOLLRIG like receptorsNOD

Scavanger receptors

C type lectin receptors

Mannose recognizing receptors

MaMaccrorophage/Dendritic cellphage/Dendritic cell

TLR5TLR5

FlageFlagelllinlin

VViirusrus

TLR3TLR3

ddssRNARNA

TLRs RECOGNIZE VARIOUS MICROBIAL STRUCTURES

TLR2TLR2

PeptidoglycanePeptidoglycane

Gram+

TLR4TLR4

LPSLPS

TLR6TLR6

Gram-

InterferonInterferonproducing cellproducing cellPC/DCPC/DC

IFN

BaBacctteeririaa

CpG DNACpG DNA

TLR9TLR9TLR7TLR7TLR8TLR8

ssRNSssRNS

TLR receptors:

• Intracellular and cell surface sensors.• Viral RNA, non-methylated DNA characteristic of bacteria, bacterial flagella, bacterial surface components (lipoproteins, peptidoglicans) and fungi structures.• Partial overlapping recognition between NOD and RIG like receptors.

TLRs Ligands: Microorganism recognized:

Cells carrying receptor:

Cellular location:

TLR1:TLR2Lypopotreins

lypoteichoic acid proteoglycan

zymosam

BacteriaParasites

DCs, mono, Eos/Baso, mast

cells

Plasma mem.

TLR2:TLR6 -”-G+ Bacteria

Fungi -”- Plasma mem.

TLR3 dsRNA Viruses NK cells Endosomes

TLR4:TLR4 LPS G- Bacteria Mϕ, DCs Plasma mem.

TLR5 Flagellin Motile Bacteria Intestinal Epi. Plasma mem.

TLR7 ssRNA VirusespDCsB cells

Eos/BasoEndosomes

TLR8 ssRNA Viruses NK cells Endosomes

TLR9Unmethylated

CpG-ODN (ssDNA)

BacteriaViruses

pDCsB cells

Endosomes

NOD like receptors

NOD-like receptors:• Intracellular receptors.• Recognizing intracellular pathogen and danger signals.• Partial overlapping recognition with TLRs.

RIG receptors:

•Intracellular sensors.

•Recognizing viral RNA, inducing an anti-viral response.

•Partial overlapping recognition with TLRs.

Additional PRRs:

EEukarukaryotesyotes

GlucosamineGlucosamine

MannMannoseoseGalactoseGalactoseSiallic acidSiallic acid

MannMannózóz

ProkaryotesProkaryotes

Macrophage / Dendritic cellMacrophage / Dendritic cell

MannMannose receptorsose receptors

BaBacteriucteriumm

MannMannoseose

direct connetion between innate cells

and pathogen)(

Specificity of innate immunity

Few receptors (20-30) are responsible for the recognition of all the pathogens

!

OPSONIZATIONOPSONIZATION ! !

Main opsonins:antibodiesComplement fragmentsAcute-phase proteins

Opsonization facilitate and accelerate the recognition of the pathogen by phaogocytes,opsonins form a bridge between pathogen and a phagocyte connecting them.

Soluble mediators

Pathogen recognition by innate immune system 1. Directly via PRR

2. Indirectly via opsonization



Effector functions, elimination of pathogens



INNATE IMMUNITY II

Effector functions, elimination of pathogens

1. Phagocytosis2. Killing with soluble mediators

3. Complement system4. NK cell activation

!!

DegradationACTIVATION

Uptake

PHAGOCYTOSIS

Phagocyte

PRR

0.5 - 1 hours

The amount of internalized particles is limited

Bacterium

Intracellular killing

Antigen presentationT cell

ACQUIRED IMMUNITY

THE PHTHE PHAGOCYTAGOCYTICIC SYSTEM SYSTEM

MACROPHAGMACROPHAGES ES DENDRITIC CELLDENDRITIC CELLS NEUTROPHILSS NEUTROPHILS

Phagocytic cellsPhagocytic cells

-MacrophagesMacrophages

-DendritiDendritic cellsc cells

-NeutroNeutrophilphil granuloc granulocytes ytes

(No presentation on MHC II)(No presentation on MHC II)

Professional Professional

antigen presenting cells antigen presenting cells

-MacrophagesMacrophages

-DendrDendritic cellsitic cells

- B lymphocytesB lymphocytes

(no killing action, only Ag presentation)(no killing action, only Ag presentation)

PHAGOCYTOSIS

Extracellular pathogen phagocytosis and killing

Soluble mediators reeased from macrophages, granulocytes are responsible for kiliing of extracellular pathogens

ROS reactive oxigen speciesNO nitric oxide

Destructive enzymes, antimicrobial substances

2.

Intracellular bacterial evasion ofkilling in phagocytes

Defensins

Phagosome acidification

Phagosome–lysosome fusionLysosomal enzymes

Intraphagolysosomal killing

ROI

RNI

Iron starvation

Tryptophan starvation

Macrophage effector capacity

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

3.

NK cellsMajor differences between NK cells and B/T lymphocytes:

Contain large cytoplasmic granules.

Responds fast, circulate in a partly activated state.

Do not express surface receptors produced by rearranged genes.

Have a range of cell-surface receptors that deliver activating or inhibitory signals

Have two main types of receptors: Ig-like Rs and the Lectin-like Rs (inhibitory and activating) that recognize altered cell surface proteins as a result of a virus infection.

Overall balance of inhibitory or activating signals decides if the NK cell killing action will take place.

Individual NK cells express different combinations of receptors- heterogeneity repertoire of responses to pathogens.

Killing of the cells infected with intracellular pathogens

KAR KIR

KIR – Killer Inhibitory Receptor association to MHC I

KAR – Killer Activatory Receptor

NK

TargetMHC+

NK

KAR KIR

TargetMHC-

!

1. The activity of NK cells is enhanced by activatory receptors

2. Inhibitory receptors block NK cell activity. Self cells are protected by inhibitory receptors.

3. Infection or tumors may increase the amount of activation and/or decrease the efficacy of inhibition

Inhibition of lysis

lysis

Adaptive components are also able to activate NK cells

ADCC-Antibody Dependent Cell Cytotoxicity

Activating NK cells through FcR on NK cells recognizing pathogen-bound Antibodies

Lysis of infected cell

ACTIVATION OF NATURAL KILLER CELLS

Kinetics of the activity of the complement system and NK

cells in virus infection

IFNIL-12

2 4 6 8 101 3 5 7 9 1211 13

Complement system

NK-cells

days

Rel

atív

szi

nt/a

ktiv

itás

NK-CELLS

Virus-infectedcell

PRR

RECOGNITIONACTIVATION

RECOGNITION OF ALTERED HOST CELLS

RECOGNITION RECEPTORECOGNITION RECEPTORRS, SIGNAL TRANSDUCTION, S, SIGNAL TRANSDUCTION, PHAGOCYTOSISPHAGOCYTOSIS, , EFFECTOR MECHANISMEFFECTOR MECHANISM

Pattern recognitionReceptors (PRRs)

Engagement of PRRs triggers phagocytosis

and cytokine production

Recognition of PAMP or DAMP induce inflammation

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 cytokines in

bacterial infection

TNF-IL-1IL-6

Few hours

ACUTE PHASE RESPONSE

Bacterium

LPS

DANGER SIGNAL

ACTIVATION

PRR

Reminder

INTERFERON RESPONSEINTERFERON RESPONSE

Besides virus infected cells..

Plasmacytoid dendritic cells (pDCs) 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

EFFECTS OF TYPE I INTERFERONS

vírus

Activate cellular genes that destroy viral mRNA and inhibit translation of

viral proteins

NK cells have a basal cytotoxicity level that is

increased up to x100 fold with the exposure to type I IFNs and produce IFN-γ when

exposed to IL-12

Helping the initiation of effector T cells- adaptive immune

response.

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

TRIF

TANK

IKKε TBK1

IRF-3

TRIF

TRAM

TLR3

TLR4

MyD88

IRF-5

TLR7TLR8TLR9

IFN-β, IFN-α1

RIG-1

Stimulation of Ig-productionby B-cells

Type I interferon receptor

IRF-7

Increased cytotoxicity and proliferation of NK-cells

Activation of - and γδ T-cells

Increased antigen presentationin myeloid dendritic cells

IRAK-1

TRAF-6

IRF-7

MULTIPLE EFFECTS OF TYPE I INTERFERONS

on immune cells

INTERFERON EFFECTOR PATHWAYSinduction of the „antiviral state”

1. Mx GTPase pathway– block viral transcription

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, preventing viral protein synthesis

4. ISG15 ubiquitin-like pathway– modify protein function

CELLULAR GENES THAT CONTROL ALL STEPS OF VIRAL REPLICATION

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

http://en.wikipedia.org/wiki/STAT_protein

http://en.wikipedia.org/wiki/STAT_protein

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

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 cytokines in

bacterial infection

TNF-IL-1IL-6

Few hours

ACUTE PHASE RESPONSE

Bacterium

LPS

DANGER SIGNAL

ACTIVATION

PRR

Reminder

RECEPTORS ON MACROPHAGES

TLR4 + CD14

MHCI

MHCII

TLR – pathogen pattern

CR1 (CD35)

CR3 (CD11b/CD18)

LFA1 (CD11a/CD18)

FcRIII (CD16)

FcRII (CD32)

FcRI (CD64)

Ag + IgG complex

Mannose receptor

Scavanger receptor

RECEPTOR LIGAND FUNCTION

FcR IgG, IgE Opsonized phagocytosis, ADCC, release of inflammatory mediators

CR3 iC3B, ICAM-1 Opsonized phagocytosis

Macrophage Mannose Receptor

Lectin Endocytosis, phagocytosis, antigen capture and transport

SR-A LPS, polianions, lipoteikolic acid

Endocytosis, phagocytosis, adhesion

CD14 LPS Transduces LPS activation , TNFa release

CCR1 MIP1a, MCP-3 Recruitment, migration of monocytes

CCR3 Eotaxin Haematopoiesis, HIV-1 coreceptor

CCR5 MIP1 Haematopoiesis, HIV-1 coreceptor

CXCR4 SDF-1a Haematopoiesis, HIV-1 coreceptor

Receptors and molecules of macrophages



Cell activation Increase in MHC, co-stimulation, killing efficiency (ROI, NO, lysosomal enzymes) and cytokine secretion

Phagocytosis and Antigen processing Intracellular – degradation in Proteosomes

Extracellular – Endiocytosis then degradation in Phagolysosomes

Antigen presentation Intracellular – on surface MHC I complex proteins


Primary lymphoid organs : - Bone marrow - Thymus Secondary lymphoid organs: - Spleen - Lymphatic...

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Transcript of Primary lymphoid organs : - Bone marrow - Thymus Secondary lymphoid organs: - Spleen - Lymphatic...