Transcript NK receptors

固有免疫
Innate immunity
Qingqing Wang （王青青）
Institute of immunology, ZJU
[email protected]
Contents
• Innate immunity
• Components of the innate immune system
• PAMPs and PRRs
• Innate immune response
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Innate Immunity
First Line of Defense
Characteristics:
- rapid
- does not generate immunologic memory
- dependent upon germline encoded receptors recognizing structures
common to many pathogens
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Characteristics of Innate and
Adaptive Immunity
Innate Immunity
Antigen independent
pattern recognition
No time lag
Not antigen specific
No memory
Adaptive Immunity
Antigen dependent
TCR/BCR
A lag period
Antigen specific
Memory
Functions
• Innate immunity is the initial response to microbes that
prevents, controls, or eliminates infection of the host by
many microbes.
• Innate immune mechanisms recognize the products of
damaged and dead host cells and serve to eliminate these
cells and to initiate the process of tissue repair.
• Innate immunity to microbes stimulates adaptive immune
responses and can influence the nature of the adaptive
responses to make them optimally effective against
different types of microbes.
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Innate Immune System
1. Physical, chemical，microbial barriers
- physical barriers include skin and mucus membranes (epithelial)
- chemical barriers include stomach acidity, secreted anti-microbial
peptides, defensins (防御素), cathelicidins (抗菌肽)
- Normal bacterial flora
2. Cells
- macrophages, neutrophils, DC, NK, B1, T, NKT…
3. Blood proteins
- Complement and mediators of inflammation
4. Cytokines
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Barrier
Skin-mucosal barrier
Physical barrier
Chemical barrier
Biological barrier
Blood brain barrier
Blood placental barrier
Epithelial defense mechanisms
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防水脂质层
板层小体：防御素和抗菌肽
Gut epithelium
表皮 Epidermis of skin
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What happens when the physical and chemical
barriers are breached?
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Leukocyte Players of Innate
Immune Responses
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Innate-like lymphocytes（ILLs）
- Unique, minor subsets of T and B lymphocytes that undergo receptor gene
rearrangements to generate receptor diversity (unlike NK cells)
- These subsets express limited receptor diversity, utilizing only a small number of
receptor gene segments
- Tend to found in specific locations in the body, usually sites that encounter
exogenous antigens or pathogens
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NK T cell
Distribution
bone marrow, liver, thymus,
spleen, peripheral blood, lymph node
NK T ＜1% in blood T cells；
NK T in liver (mouse 30%，human 4%）
NK T cell
1, cytokine:
IL-4, IFN-, IL-12
2, cytotoxity
perforin and FasL/Fas
3, MCP-1, MIP-1
T细胞
Surface marker：TCR、CD4-CD8-、CD8+
distribution：mucosa of skin、intestine、lung and
genitals
restriction：non-classical MHCⅠmolecules
restriction
classification：epidermis T cell
systemic T cell
T cell：function
Anti-infection
Immune surveilence
Immune regulation
Immune tolerance
Anti-tumor
B1 cell
• B1 cell mainly located in abdomen cavity,
thorax and intestines
• B1 cell recognize LPS and capsular
polysaccharide
• IgM antibody
• No class switch and immune memory
1. Two types of phagocytes
(1) Neutrophil granulocytes
phagocytosis, intracellular
killing, inflammation and
tissue damage
characteristic nucleus,
cytoplasm
granules and CD67
membrane marker.
(2) Monocytes and macrophages
phagocytosis,
intracellular and extracellular killing, tissue
repair, antigen
presentation for specific
immune response
characteristic nucleus and
CD14 membrane marker.
（2）monocyte/macrophage
macrophage
Dendritic cells, DC
• cDC
myeloid DC, conventional DC
• pDC (plasmacytoid DC)
TLR7,9 type I interferon
Innate-like lymphocytes（ILLs）
- Unique, minor subsets of T and B lymphocytes that undergo receptor gene
rearrangements to generate receptor diversity (unlike NK cells)
- These subsets express limited receptor diversity, utilizing only a small number of
receptor gene segments
- Tend to found in specific locations in the body, usually sites that encounter
exogenous antigens or pathogens
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Complement system：
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Cytokines of innate immunity
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TNF
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IL-1
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Innate Immune Receptors

Innate immune receptors are not clonally distributed

Binding of receptors results in rapid response

Innate immune receptors mediate three functions:
- phagocytic receptors to stimulate pathogen uptake
- chemotactic receptors that guide phagocytes to site of infection
- stimulate production of effector molecules and cytokines that induce
innate responses and also influence downstream adaptive immune responses
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Pathogen Recognition

Most microorganisms express repeating patterns of molecular
structures termed Pathogen Associated Molecular Patterns
(PAMPs)

Endogenous molecules that are produced by or released from
damaged and dying cells are called Damage-Associated Molecular
Patterns (DAMPs)

Innate immune system has evolved mechanisms capable of
recognizing these repeating patterns termed Pattern Recognition
Receptors (PRRs)
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免疫识别的危险模式理论
Danger signal
Danger Theory
Polly Matzinger 理论免疫学家
PAMPs
DAMPs
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Structure of bacteria
pilin for
DNA
adhesion
shape and
rigidity
flagellum for
motion
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Shared features of bacteria: cell walls
胞壁酸
lipopolysaccharide
proteins
teichoic acid
proteins
OM
peptidoglycan
peptidoglycan
IM
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Peptidoglycan 肽聚糖
teichoic acid
proteins
peptidoglycan
N-乙酰氨基葡糖和N-乙酰胞壁酸交替的杂多糖
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Lipopolysaccharide 脂多糖
OM
peptidoglycan
IM
lipid 45
A类脂质A
Flagellin 鞭毛
钩状体
丝状体
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Bacterial DNA
Bacteria
• Frequent CG sequences
• Cytosine not methylated
Mammals
• Rare CG sequences
• Cytosine in CG is methylated
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Viruses and double-stranded RNA
• Some viruses have dsRNA genomes (rare)
• Many more viruses have single-stranded
RNA genomes but produce dsRNA during
replication and mRNA synthesis
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Engagement of innate immunity
• Recognition of organisms based on conserved
patterns
–
–
–
–
–
Lipopolysaccharide (gm-)
Peptidoglycan (most bacteria)
Flagella (many bacteria)
Unmethylated CpG in DNA
Single-stranded RNA (viral)
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Pathogen Recognition

Examples of Pattern Recognition Receptors (PRRs) :
- Mannose-Binding Lectin (MBL)
- Macrophage Mannose Receptor
- Scavenger Receptors
- Toll-like Receptors (TLRs)
- RIG-I like Receptors (RLRs)
- Nod-like Receptors (NLRs)
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Toll-like receptors
single stranded
RNA
TLR8
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Toll-Like Receptors (TLRs)
TNF
IFN
Cellular Localization:
- Lysosomal localization (i.e. subcellular) of TLR-3 and TLR7,8,9
- TLR-3 and 7,8,9 recognize viral/bacterial nucleic acids
- lysosomal expression isolates pathogen nucleic acid recognition away from
potential cross-reaction with host mammalian nucleic acid motifs
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RLRs：Retinoic Acid-Inducible Gene-I-like Receptors
RD
RIG-I , Retinoic Acid-Inducible Gene-1
MDA5, Melanoma Differentiation-Associated Gene 5
CARD-containing; melanoma growth-suppressive properties
LGP2, Laboratory of Genetics and Physiology 2
DExH/D-box motif and a carboxy-terminal helicase domain
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RIG-I Like Receptors (RLRs)
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Nod-like receptors (NLRs)
• Nucleotide-binding and
oligomerization domain
(NOD)-like receptors
• Cytoplasmic proteins
• At least 22 members
• Recognize microbial
components
• Work synergistically with
TLR
MDP：胞壁酰二肽
iE-DAP：γ谷氨酰基二氨基庚二酸
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NOD-I Like Receptors
(NLRs)
NLRs are cytoplasmic
bacterial sensors
14 NLRPs
 activate IL-1β
Inflammasome
IPAF/NLRC4
NLRP3
NLRP1
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Cell-associated PRRs
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Other cell-associated PRRs
二酰基甘油酯
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Soluble recognition and effector molecules
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Summary and
Review of Innate
Immune Responses
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Correlation between innate immunity
and adaptive immunity
• Initiation of adaptive immunity
• Influence on type of adaptive immunity
• Participate in effect phase of adaptive
immunity
NK cells
u NK cells were defined initially
by their ability to lyse certain
tumor cell lines and virally
infected cells without prior
immunization, and so mediate
a form of innate (or natural)
immunity that is termed
“natural killing”.
Surface markers
1. CD56
2. CD16(FcγRⅢ) ADCC
3. FcR
NK cells are generally TCR- , mIg-, CD16+,
CD56+.
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Natural killer cells
• Development
• Receptors
• Function
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NK receptors
Activation of NK cells is the net effect of inhibitory and activating signals
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The receptors associated with
activation or inhibition
1.The receptors recognizing MHCⅠmolecules
(1) Killer immunoglobulin-like receptor, KIR
KIR 2DL
KIR 2DS
ITIM inhibitory receptor
binding with DAP-12( ITAM)
activating receptor
KIR 3DL ITIM inhibitory receptor
KIR 3DS binding with DAP-12( ITAM)
activating receptor
Intracellular signaling pathways coordinate inhibitory and
activating signals
(2) Killer lectin-like receptor, KLR
CD94
NKG2A ITIM
inhibitory receptor
CD94
NKG2C binding with DAP-12( ITAM)
activating receptor
NK receptors: ‘Defense is the best offense”
While both KIRs and KLRs sense the presence
(absence) of MHC class I molecules, activating
as well as inhibitory receptors are found in both
families of receptors.
- The KIRs are subdivided according to the
number of immunoglobulin-like domains (2 or
3 domains) and the length of their cytoplasmic
tail: Short tail = activating receptors
Long tail = inhibitory receptors
- The KLR are heterodimers of CD94
associated with a NKG2 molecule. Six distinct
NKG2 isoforms exist in humans.
NKG2C/CD94 = activating receptor
NKG2A/CD94 = inhibitory receptor
NKG2B/CD94 = inhibitory receptor
NKG2D homodimer = activating receptor.
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(3) The significance of KIR and KLR
NK cells are prevented from killing host cells
because they recognize the host classⅠMHC
molecules. Thus, they only attack cells whose
classⅠMHC molecules are lost or altered, as occurs
frequently in malignancy or viral infection.
2. The receptors recognizing non-MHCⅠ
molecules
(1) NKG2D
binding with DAP-10 ( ITAM)
activating receptor
ligand: MⅠC A/B (on some tumor cells)
(2) natural cytotoxicity receptor, NCR
NKp46,NKp30 binding with CD3(  )
NKp44 expressed on activated NK cells
binding with DAP-12 ( ITAM)
activating receptor
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Functions of NK cells
1. Anti-infection
provide an early innate barrier to infection by
eliminating infected host cells
2. Anti-tumor
kill tumor cells directly: perforin, granzymes,
ADCC
3. Immunoregulation
Activated NK cells produce cytokines such as IFN-,
TNF-, G-CSF. These cytokines can activate T cells.
Functions
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The mechanism of cytotoxicity
1. Perforin / granzyme pathway
2. Fas / FasL pathway
3. TNFα / TNFR-1
target cell apoptosis
Release of cytotoxic granules at the site of contact with infected cells
NK cell
Target cell
- First contact between a CTL or NK cell with infected cells is via non-specific binding of adhesion molecules
(LFA-1 (blue) on T and NK cells with ICAM-1 or ICAM-2 (brown) on target cells). This makes a channel between
the target and the cytotoxic cell.
- Specific antigen/MHC class I recognition by TCR on CTL, or engagement of the NK’s natural cytotoxic
receptors (NCR) (green) by non-MHC ligands (orange) on the surface of the target cell. This results in a
polarization of the cell: the actin cytoskeleton (green staining in the immunofluorescence microscopy) at the site of
contact is reorganized as to aligning the microtubule-organizing center (MTOC), as well as the secretory
apparatus, including the Golgi (GA). The GA-derived lytic granules (stained in red in the photomicrograph) are
specifically directed onto the target cell.
- The content of the granules is directly released onto the target cell.
Why are NK cells prominent tumor killers?
Similar to many pathogens, tumor cells
can escape the adaptive immune system,
by downregulating the expression of
MHC class I.
This makes them more susceptible to
NK cells.
- The regression of transplanted tumors in a normal mouse model (blue line) is largely due to the action of CTLs recognizing tumor
antigens presented on MHC class I (right panel). Albeit the presence of NK cells, this regression is absent in nude mice (red line) in
which CTLs do not develop.
-Tumor variants that express low levels of MHC class I become susceptible to NK cells, especially in nude mice (have higher levels of
NK cells than wild type mice). Thus tumors that are sensitive to NK killing grow less well in nude than normal mice (central panel).
- Transfection of MHC class I genes resulting in high expression of this protein restores NK cell resistance but susceptibility to CTL in
normal mice (left panel; blue line).
Thanks for your attention!
If you have any questions,
please feel free to contact me:
[email protected]