Download Innate immunity 2015-16

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 act in an autocrine way, in a paracrine way,
or in an endocrine way 
 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.
!
Categories of cytokines
 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
The two „arms” of the immune system
Innate immunity: always present (ready to attack); many pathogenic
microbes have evolved to resist innate immunity
Adaptive immunity: stimulated by exposure to microbe; more potent !
Both the innate and adaptive arms of immunity are required for
elimination of pathogens
Macrophages use pathogen-specific receptors (PRR)
to engulf and destroy pathogens and induce inflammation
Innate immune mechanisms establish a
state of inflammation at sites of
infection.
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
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)!
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
Innate immunity as a first line of defence
Innate immune cells recognize conserved 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).
PRR types
TOLL
RIG
like receptors
NOD
Scavanger receptors
C type lectin receptors
Mannose recognizing receptors
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.
PAMPs- Pathogen associated molecular patters
Structures on pathogens recognized by the innate cells
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-like
receptors:
•Intracellular sensors.
•Recognizing viral RNA,
inducing an anti-viral response.
•Partial overlapping recognition
with TLRs.
Additional PRRs:
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
FcRs
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
2.
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 killing of extracellular pathogens
ROS reactive oxigen species
NO nitric oxide
Destructive enzymes, antimicrobial substances
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
MECHANISMS OF INNATE IMMUNITY
ACTIVATION OF NATURAL KILLER CELLS
NK-CELLS
PRR
Virus-infected
cell
RECOGNITION
ACTIVATION
Lysis of infected cell
RECOGNITION OF
ALTERED HOST CELLS
Kinetics of the activity of the
complement system and NK
cells in virus infection
Relative level/activity
IFN
IL-12
NK-cells
Complement system
1
2
3
4
5
6
7
8
9 10 11 12 13
days
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
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
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
EFFECTS OF TYPE I INTERFERONS
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
CELLULAR GENES THAT CONTROL
ALL STEPS OF VIRAL REPLICATION
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)
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