Transcript 3 Innate immunity I

!!
LYMPHOID ORGANS
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)
THE TWO ARMS OF THE IMMUNE SYSTEM
Monocytes, Macrophages,
Monocytes, Macrophages,
Dendritic cells, Granulocytes, NK
Dendritic cells, Granulocytes, NK
cells and Complement components
cells and Complement components
B and T cells
!!
Professional phagocytic cells
macrophages
neutrophyl granulocytes
dendrtitic cells
!!
the phagocytosed cells or molecules may modify
the functions of the cell
phagocytosis followed by enzymatic degradation
Professional antigen presenting cells
macrophages
B lymphocytes
dendrtitic 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 cells
are 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
How do immunocytes communicate:
Soluble mediators
Infection
CYTOKINES & CHEMOKINES
Phagocyte activation
Soluble 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
Cell killing
CTL
Target cell
T
Y
Antigen presentation
B
T
Antibody production
Activation of accessory cells
Dendritic cell macrophage
THE MOST IMPORTANT FEATURES OF CYTOKINES
 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.
!
 Cytokines can be devided into sub-groups by origin and
functional properties.
Functional groups:
Inflammatory cytokines
Direct the development and maturation of immune cells
Direct activation and differentiation of immune cells
Categories of cytokines
hormons
cytokines
interleukins
chemokine
interferons
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
PRR Pattern recognition
immune system,
receptors
macrophage, dendritic cells
Danger signal and
Pathogen recognition
mainly in the innate immun
system
B cells
BCR (B cell receptor)
T cells
TCR (T cell receptor)
All nucleated cells in
human
MHC (MHCI) Major
Histocompatibility
Complex
Antigen recognition of B
cell
Antigen recognition of T
cell
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
Stomach
 pH of 3-4
 Pepsin
Skin





Tight junctions
Keratin layer
Antibacterial peptides; Defensins
pH of 5.5
Fatty acids
Burns and susceptibility to infections!
Eye
 Tear film (Oils, lactoferin, mucin and lyzosyme)
Vagina
 pH of 3.8-4.5
 Lactobacillus  Lactic acid
Respiratory tract
 Cilliary movement
 Coughing, sneezing
Impaired cilia movement (CF)!
Monocite /
macrofage
Recogni
-tion
Cell-cel
(APC)
Communi
cation
Soluble
effector
function
DC
Mast
cell
Granulocites
NK cell
B cell
T cell
Complement
INNATE IMMUNITY
Pathogen 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
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….
Recognition is inevitable
!!
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).
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….
Recognition is inevitable
!!
PAMPs- Pathogen associated molecular patters
Structures on pathogens recognized by the innate cells
PRR types
TOLL
RIG
like receptors
NOD
Scavanger receptors
C type lectin receptors
Mannose recognizing receptors
TLRs RECOGNIZE VARIOUS MICROBIAL STRUCTURES
Bacteria
Virus
CpG DNA
ssRNS
dsRNA
Peptidoglycane
Gram+
TLR3
IFN
TLR7
TLR8
TLR2
Interferon
producing cell
PC/DC
Flagellin
LPS
Gram-
TLR4
TLR6
TLR9
Macrophage/Dendritic cell
TLR5
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
TLR1:TLR2
Ligands:
Lypopotreins
lypoteichoic acid
proteoglycan
zymosam
Microorganis
m recognized:
Cells
carrying
receptor:
Cellular
location:
Bacteria
Parasites
DCs, mono,
Eos/Baso, mast
cells
Plasma mem.
-”-
Plasma mem.
TLR2:TLR6
-”-
G+ Bacteria
Fungi
TLR3
dsRNA
Viruses
NK cells
Endosomes
TLR4:TLR4
LPS
G- Bacteria
Mϕ, DCs
Plasma mem.
TLR5
Flagellin
Motile Bacteria
Intestinal Epi.
Plasma mem.
Endosomes
TLR7
ssRNA
Viruses
pDCs
B cells
Eos/Baso
TLR8
ssRNA
Viruses
NK cells
Endosomes
Bacteria
Viruses
pDCs
B cells
Endosomes
TLR9
Unmethylated
CpG-ODN
(ssDNA)
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:
Prokaryotes
Eukaryotes
Mannóz
Glucosamine
Galactose
Siallic acid
Mannose
Mannose
Bacterium
Mannose receptors
Macrophage / Dendritic cell
Specificity of innate immunity
(
)
!
direct connetion
between innate cells
and pathogen
Few receptors (20-30) are responsible for the recognition of all the pathogens
OPSONIZATION
!!
Opsonization facilitate and accelerate the recognition of the pathogen by phaogocytes,
opsonins form a bridge between pathogen and a phagocyte connecting them.
Main opsonins:
antibodies
Complement fragments
Acute-phase proteins
Soluble
mediators
Pathogen recognition by innate immune system
1. Directly via PRR
2. Indirectly via opsonization
INNATE IMMUNITY
Pathogen recognition
 PRRs (TLRs, C type lectins, Mannose and Glucan binding lectins,
NLRs and RIG-I helicases)
Effector functions, elimination of pathogens
Communication/ Antigen presentation 
 Intracellular – on surface MHC I complex proteins
Extracellular – on surface MHC II complex proteins
INNATE IMMUNITY II
Effector functions, elimination of pathogens
1. Phagocytosis
2. Killing with soluble mediators
3. Complement system
4. NK cell activation
!!
PHAGOCYTOSIS
PRR
Degradation
ACTIVATION
Bacterium
Phagocyte
Uptake
Intracellular killing
0.5 - 1 hours
The amount of internalized
particles is limited
Antigen presentation
T cell
ACQUIRED IMMUNITY
THE PHAGOCYTIC SYSTEM
MACROPHAGES
DENDRITIC CELLS
NEUTROPHILS
Phagocytic cells
Professional
antigen presenting cells
-Macrophages
-Macrophages
-Dendritic cells
-Dendritic cells
-Neutrophil granulocytes
- B lymphocytes
(No presentation on MHC II)
(no killing action, only Ag presentation)
PHAGOCYTOSIS
Extracellular pathogen phagocytosis
and killing
Extracellular pathogen phagocytosis
and killing
2.
Soluble mediators reeased from macrophages, granulocytes are
responsible for kiliing of extracellular pathogens
ROS reactive oxigen species
NO nitric oxide
Destructive enzymes, antimicrobial substances
Intracellular bacterial evasion of
killing in phagocytes
Macrophage effector capacity
Defensins
Phagosome acidification
Phagosome–lysosome fusion
Lysosomal enzymes
Intraphagolysosomal killing
ROI
RNI
Iron starvation
Tryptophan starvation
3.
COMPLEMENT ACTIVATION
COMPLEMENT
Complement-proteins
Lysis of bacteria
Inflammation
Chemotaxis
Bacterium
Lectin pathway
Alternative
pathway
Complement-dependent
phagocytosis
Antigen + Antibody
Few minutes – 1 hour
ACQUIRED IMMUNITY
Enzymes get fragmented, complement activity
can be exhausted
NK cells
Major 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
1. The activity of NK cells is
enhanced by activatory
receptors
2. Inhibitory receptors block
NK cell activity. Self cells lysis
are protected by inhibitory
receptors.
KAR
3. Infection or tumors may
increase the amount of
activation and/or
decrease the efficacy of
inhibition
Target
MHC+
Target
MHC-
Inhibition of
lysis
KIR
NK
KAR
KIR
NK
KIR – Killer Inhibitory Receptor
association to MHC I
KAR – Killer Activatory Receptor
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
ACTIVATION OF NATURAL KILLER CELLS
NK-CELLS
PRR
RECOGNITION
ACTIVATION
RECOGNITION OF
ALTERED HOST CELLS
Kinetics of the activity of the
complement system and NK
cells in virus infection
Relatív szint/aktivitás
Virus-infected
cell
Lysis of infected cell
IFN
IL-12
NK-cells
Complement system
1
2
3
4
5
6
7
8
9 10 11 12 13
days
RECOGNITION RECEPTORS, SIGNAL TRANSDUCTION,
PHAGOCYTOSIS, EFFECTOR MECHANISM
Pattern recognition
Receptors (PRRs)
Engagement of PRRs
triggers phagocytosis
and cytokine
production
INNATE IMMUNITY
Pathogen 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 of PAMP or DAMP induce inflammation
Reminder
INFLAMMATION – ACUTE PHASE RESPONSE
PRR
TNF-
neutrophil
LPS
IL-12
DANGER
SIGNAL
ACTIVATION
IFN
Few hours
LPS (endotoxin) (Gram(-) bacteria)
ACUTE PHASE
RESPONSE
Kinetics of the release of proinflammatory cytokines in
bacterial infection
macrophage
cytokines
TNF-
IL-1
Plasma level
Bacterium
NK-cell
TNF-
IL-1
IL-6
IL-6
1
2
3
4
5
hrs
INNATE IMMUNITY
Pathogen 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
INTERFERON 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.
VIRUS INDUCED TYPE I INTERFERON PRODUCTION
Type I IFN receptor
IFN response
Virus
IFN-
IRF-3
NFB
AP-1
IRF-3
IFN-
paracrine
IFN-
IRF-7
autocrine
Infected cell
IFN response
IFN-
subtypes
IRF: interferon regulatory factor
MULTIPLE EFFECTS OF TYPE I INTERFERONS
on immune cells
Increased cytotoxicity and
proliferation of NK-cells
TLR4
TRAM
TRIF
TLR7
TLR8
TLR9
TLR3
TRIF
MyD88
IRAK-1
TRAF-6
TANK
Activation of - and γδ T-cells
RIG-1
IKKε
TBK1
IRF-7
IRF-3
IRF-5
IFN-β, IFN-α1
Increased antigen presentation
in myeloid dendritic cells
IRF-7
Type I interferon receptor
Stimulation of Ig-production
by B-cells
INTERFERON EFFECTOR PATHWAYS
induction 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, dsRNAdependent)
– inhibit translation, preventing viral protein synthesis
4. ISG15 ubiquitin-like pathway
– modify protein function
LULAR GENES THAT CONTROL ALL STEPS OF VIRAL REPLICA
Type I. IFN receptor
Type III. IFN receptor (IFNλ)
IFNAR1/2
IFNLR1
IL-10R2
Type II. IFN receptor
IFNG1/2
JAK2
TYK2
JAK1
TYK2
JAK1
STAT1
STAT2
P
JAK2
JAK1 JAK1
Signal Transducers and
Activators of Transcription
STAT1
Plasma membrane
Cytoplasm
STAT1
ISGF-3
P STAT2
STAT1
IRF9
P
P STAT1
Interferon-stimulated genes
STAT1
P
STAT1
P STAT2
ISRE
ISG15, Mx,
OAS and
PKR
Antiviral immunity Interferon-stimulated
Regulatory elements
P
Nucleus
P STAT1
GAS: Gamma
Activating sequence
GAS – promoter elements
Antimycobacterial immunity
Oligomer
accumulation
in cytoplasmic
membranes
(e.g. ER)
MxA oligomer
Mechanism of action of
MxA, OAS1 and PKR
MxA monomer
(Cytoplasm)
ISRE
MxA
(Nucleus)
synthetized
pppA(2’p5’A)n
inactive
RNaseL
monomer
Trapped viral
components
P
EIF2
EIF2
Active PKR dimer
Active OAS1 tetramer
active
RNaseL
dimer
Induction by
viral RNAs
Induction by
viral dsRNA
Inactive PKR monomer
Inactive OAS1 monomer
cleaved RNA
ISRE
(Cytoplasm)
OAS1
(Nucleus)
Inhibition of
translation
(Cytoplasm)
ISRE
PKR
(Nucleus)
Reminder
INFLAMMATION – ACUTE PHASE RESPONSE
PRR
TNF-
neutrophil
LPS
IL-12
DANGER
SIGNAL
ACTIVATION
IFN
Few hours
LPS (endotoxin) (Gram(-) bacteria)
ACUTE PHASE
RESPONSE
Kinetics of the release of proinflammatory cytokines in
bacterial infection
macrophage
cytokines
TNF-
IL-1
Plasma level
Bacterium
NK-cell
TNF-
IL-1
IL-6
IL-6
1
2
3
4
5
hrs
RECEPTORS ON MACROPHAGES
TLR4 + CD14
Scavanger receptor
Mannose receptor
FcRI (CD64)
Ag + IgG
complex
MHCI
TLR – pathogen
pattern
FcRII (CD32)
MHCII
FcRIII (CD16)
LFA1 (CD11a/CD18)
CR1 (CD35)
CR3 (CD11b/CD18)
FcRs
Receptors and molecules of macrophages
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
INNATE IMMUNITY
Pathogen recognition
 PRRs (TLRs, C type lectins, Mannose and Glucan binding lectins,
NLRs and RIG-I helicases)
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
Extracellular – on surface MHC II complex proteins