qingqing wang （王青青） institute of immunology, zju [email protected] 固有免疫 innate...
TRANSCRIPT
Contents
• Innate immunity
• Components of the innate immune system
• PAMPs and PRRs
• Innate immune response
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Innate ImmunityFirst 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
Characteristics of Innate and Adaptive Immunity
Antigen independent
pattern recognition
No time lag
Not antigen specific
No memory
Antigen dependent
TCR/BCR
A lag period
Antigen specific
Memory
Innate Immunity Adaptive Immunity
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 barrierPhysical barrier Chemical barrierBiological barrier
Blood brain barrierBlood placental barrier
Epithelial defense mechanisms
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表皮 Epidermis of skin
Gut epithelium
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防水脂质层板层小体：防御素和抗菌肽
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
Surface marker ： TCR 、 CD4-CD8- 、 CD8+
distribution ： mucosa of skin 、 intestine 、 lung and genitals
restriction ： non-classical MHC molecules Ⅰrestriction
classification ： epidermis T cell
systemic T cell
T 细胞
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
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(2) Monocytes and macrophages
phagocytosis, intracellular and extra-cellular killing, tissue repair, antigen presentation for specific immune response
characteristic nucleus and CD14 membrane marker.
（ 2 ） monocyte/macrophage
macrophage
• cDC
myeloid DC, conventional DC
• pDC (plasmacytoid DC)
TLR7,9 type I interferon
Dendritic cells, DC
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
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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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)
Pathogen Recognition
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免疫识别的危险模式理论Danger signalDanger Theory
Polly Matzinger 理论免疫学家
PAMPs
DAMPs
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Structure of bacteria
pilin for
adhesion
flagellum for motion
shape and rigidity
DNA
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Shared features of bacteria: cell walls
peptidoglycanpeptidoglycan
teichoic acid
proteins
lipopolysaccharide proteins
peptidoglycanpeptidoglycan
IM
OM
胞壁酸
Peptidoglycan 肽聚糖
peptidoglycanpeptidoglycan
teichoic acidproteins
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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
peptidoglycanpeptidoglycan
IM
OM
lipid Alipid A 类脂质 A
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Flagellin 鞭毛
钩状体 丝状体
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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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)
Pathogen Recognition
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Toll-like receptors
single strandedsingle stranded RNARNA
TLR8TLR8
Toll-Like Receptors (TLRs)
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
TNF
IFN
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RLRs ： Retinoic Acid-Inducible Gene-I-like Receptors
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
RD
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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
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
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二酰基甘油酯
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
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”.
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(FcγR ) ADCCⅢ
3. FcR
NK cells are generally TCR- , mIg-, CD16+,
CD56+.
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Natural killer cells
• Development
• Receptors
• Function
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Activation of NK cells is the net effect of inhibitory and activating signals
NK receptors
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The receptors associated with activation or inhibition
1.The receptors recognizing MHC moleculesⅠ(1) Killer immunoglobulin-like receptor, KIR KIR 2DL ITIM inhibitory receptor KIR 2DS 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 receptorsLong tail = inhibitory receptors
- The KLR are heterodimers of CD94 associated with a NKG2 molecule. Six distinct NKG2 isoforms exist in humans.NKG2C/CD94 = activating receptorNKG2A/CD94 = inhibitory receptorNKG2B/CD94 = inhibitory receptorNKG2D 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 class MHC Ⅰmolecules. Thus, they only attack cells whose
class MHC molecules are lost or altered, as occurs Ⅰfrequently in malignancy or viral infection.
2. The receptors recognizing non-MHC Ⅰmolecules
(1) NKG2D binding with DAP-10 ( ITAM) activating receptor ligand: M C A/B (on some tumor cells)Ⅰ
(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
- 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.
Target cell
NK cell
Why are NK cells prominent tumor killers?
- 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).
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.
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