Innate Immunity Flashcards
Major Functions of Innate immunity
Complement activation, inflammation, cell activation (cytokine and chemokine production, phagocytosis and other killing of microbes), priming of adaptive immune response
Innate immune response recognizes 3 things:
PAMPs
DAMPs
Absence of certain “self” marker molecules (by NK cells)
TLRs
transmembrane proteins that are PRRs
bind to and are activated by PAMPs and DAMPs
TLR1
Triacyllipopeptides (mycobacteria and gram-negative bacteria)
Heterodimer w/ TLR 2 –>
MyD88 –>
NF-kB –> antimicrobials, cytokines and chemokines
& MAP kinase –> AP-1 –> IFN-b and a (and above)
TLR2
Peptidoglycans (Gram +), GPI-linked proteins (trypanosomes), Lipoproteins (mycobacteria and other), Zymosan (yeast and other fungi), phophatidylserine (schistosomes)
Heterodimer w/ TLR 1 –>
MyD88 –>
NF-kB –>
& MAP kinase –> AP-1 –> IFN-b and a & antimicrobials, cytokines and chemokines
TLR 3
Homodimer ds RNA (viruses) - endosome PI3K/TRIF/TRAM --> IRF7/3 --> IFN-b, a PI3K --> MAP Kinase pathway --> AP-1 --> Also TAK1 --> MAP kinase and NF-kB --> IFNb, a & antimicrobials, cytokines, and chemokines
TLR 4
LPS (gram -), F-protein (RSV), mannans (fungi) on cell membrane AND endosome
homodimer
–> TAK1 & IRF7/IRF3
TAK1 –> MAP kinase –> AP1 & TAK1 –> NF-kB
–> IFNb/a and proinflammatory cytokines
TLR6
heterodimer with TLR2
TLR6 - diacyllipopolypeptides (mycobacteria and gram +) & zymosan (yeasts and other fungi)
signalling unknown (likely TAK1)
TLR 7
homodimer endosome - viral ssRNA MyD88 TAK1 --> MAP k and NF-kB also IRF7
IFN b/a
proinflam
TLR8
viral ssRNA - signalling unknown
TLR 9
homodimer CpG DNA/hemozoin/herpes byproducts endosome MyD88 --> TAK1 and IRF7 MAP k and NF-kB IFNb/a and proinflammatory cytokines
TLR 1 PAMPs
triacylllipopeptide (mycobacteria and gram - bacteria)
TLR 2 PAMPs
Peptidoglycans (Gram +) GPI-linked proteins (trypanosomes) Lipoproteins (mycobacteria and other) Zymosan (yeast and other fungi) Phosphatidylserine (schistosomes)
TLR 3 PAMPs
dsRNA (viruses)
TLR 4 PAMPs
LPS (gram -)
F-protein (RSV- virus)
Mannans (fungi)
TLR 5 PAMPs
Flagellin (bacteria)
TLR 6 PAMPs
Diacyllipopolypeptides (mycobacteria and gram +)
Zymosan (yeasts and other fungi)
TLR 7 PAMPs
ssRNA (viruses)
TLR 8 PAMPs
ssRNA (Viruses)
TLR 9 PAMPs
CpG unmethylated dinucleotides (bacterial DNA)
Dinucleotides
Herpes virus components
Hemozoin (malaria)
TLR 1 signaling
heterodimer with TLR 2 MyD88 TAK 1 -- MAP kinase NF-kB -- AP-1 NF-kB -- IFNa/b and proinflammatory cytokines
TLR 2 signaling
heterodimer with TLR 1 OR 6 MyD88 TAK 1 -- MAP kinase NF-kB -- AP-1 NF-kB -- IFNa/b and proinflammatory cytokines
TLR 2/1 result
IL-10 –> Th2 –> IL-4, IL-5, IL-13
TLR 3 signalling
homodimer TLR 3/3 endosome NOT MyD88 But get TAK1 and MAP kinase Also IRF7 and IRF3 IFN a/b and proinflamm
TLR 3 results
IL-12 –> Th1 –> IFN gamma
TLR 4 signalling
homodimer
cell membrane: MyD88
endosome: TRIF/TRAM
TAK 1 and IRF 7/3 –> IFN a/b and proinflamm
TLR 4 results
IL-12 –> Th1 –> IFN gamma
TLR 5 signalling
Homodimer
MyD88 –> TAK1
IFN ab and proinflamm
TLR 6 signaling
Heterodimer with 2 MyD88 TAK 1 -- MAP kinase NF-kB -- AP-1 NF-kB -- IFNa/b and proinflammatory cytokines
TLR 2/6 results
IL-10, RA, TGF-b –> Treg –> IL-10, TGF-beta
TLR 7 signalling
Homodimer
MyD88 (endosome)
TAK 1 and IRF7
IFN b/a and proinflamm
TLR 8 signaling
unknown
TLR 9 signaling
homodimer
MyD88 (endosome)
TAK1 and IRF7
IFN b/a and proinflamm
TLR 7 results
IL-12 –> Th1 –> IFN gamma
TLR 9 results
IL-12 –> Th1 –> IFN gamma
Which PRRs are TLRs?
Some PRRs that recognize PAMPs do not activate phagocytosis but rather trigger cell signaling leading to gene transcription events to combat the foreign material. These are the TLRs.
Hallmarks of inflammation
Influx of fluid (edema)
Increased temperature (hyperthermia)
Decreased oxygenation (local hypoxia)
Influx of white blood cells (extravasation)
Triggers of Inflammation
C5a stimulation of basophil/mast cell degranulation and activation
Macrophages
NK cells
Histamine
increase vascular permeability
PGE2
Vasodilation, increased vascular permeability
LTD2
Neutrophil chemotaxis, increased vascular permeability
LTD4
Increased vascular permeability
What do macrophages do to trigger inflammation
TNF
IL-1
IL-8
TNF
cause fever, stimulated expression of E-selectin
IL-1
Induction of local inflammation.
Activates endothelial cells to express adhesion molecules. Induces the production of chemokines to recruit leukocytes. Also plays a role in systemic effects such as fever, the acute phase response, and the stimulation of neutrophil production.
IL-8
chemotaxis
NK cells and inflammation
IFN gamma - activation of phagocytic cells and Nk cells
3 principle changes in tissue during acute inflammation
Increased blood supply to the affected area.
Increase capillary permeability (allows for large serum molecules to enter the tissue).
Increase in leukocyte migration into the affected tissue.
acute inflammation phases
recruit / activate leukocytes, eliminate the pathogen, resolve the damage, disappearance of leukocytes from the tissue, regenerate tissue function.
Chronic inflammation during infection
Most pathogenic organisms have developed systems to deflect immune responses that would eliminate them. In this case the body often tries to contain the infection or minimize the damage it causes. Persistent antigenic stimulus and the cytotoxic effects of the unresolved infection leads to ongoing chronic inflammation.
What cells are in acute inflammation
neutrophils and activated helper T cells
what cells are in chronic inflammation
macrophages, cytotoxic t cells and b cells
Important inflammatory cytokines
TNF-a, IL-1, IFN gamma
Important molecules in leukocyte adhesion and diapedesis
CD15 on cell attaches to E-selectin on endothelium
Chemokines (IL-8)
Integrins
Inflammatory response
- Tissue damage/bacteria –> resident sentinel cells to release chemoattractants and vasoactive factors to trigger local increase in blood flow/permeability
- Allow influx of fluid and cells
- Neutrophils and other phagocytes migrate to site of inflammation (chemotaxis)
- Phagocytes and antibacterial substances destroy bacteria
What role tissue cells in inflammation
when infected or damaged, can send signals to immune system to call for help (interferons, cytokines)
Also make defensins and cathelicidins
Neutrophils role in tissue inflammation
Primary phagocytic cell sin blood
First cells to migrate to site of inflammation/infection
Phagocytize bacteria and viruses
Can recognize antibodies
Neutrophil differentiation
IL3 + GM-CSF (myeloid progenitor) –> G-CSF = neutrophil
Eosinophils role
Phagocytosis Granules contain major basic protein vs helminths induce histamine release from mast cells activate neutrophils and platelets activated by complement to degranulate
Eosinophils differentiation
IL-3 + GM-CSF (myeloid progenitor) –> +IL-5 = Eosinophil
Mediators of delayed reaction of allergic response
Eosinophils, Th1 and basophils
Basophils role
Have IgE on surface
Mediators of delayed reaction of allergic respnse
Release histamine when IgE finds antigen
activated by complement to degranulate
Basophils differentiation
IL-3 + GM-CSF (myeloid progenitor) –> IL-4 = basophil
Monocytes role
Differentiate to form macrophages in peripheral tissues where they are first line of defense against microbial invasion
kupfer cells
liver
microglia
brain
monocytes differentiation
IL3 + GM-CSF (myeloid progenitor) –> M-CSF (monocyte)
macrophage role
late migrators to sites of inflammation (effector cells of chronic inflammation)
Major producers of cytokines and lymphokines
Phagocytosis
APCs
What cytokines/lymphokines macrophages release
IFNa (antiviral)
IL-1b, IL-6, TNF-a: fever
CXCL8 (IL-8): chemotaxis of PMNs, basophils, T cells
IL-12: activation of NK cells and CD4 Th1 T cells
IFNa
antiviral
IL1b, IL-6, TNF-a
fever
IL-8
chemotaxis of PMNs, basophils, T cells
IL-12
activation of NK cells and CD4 Th1 cells
Macrophage differentiation
(IL3 + GM-CSF) (myeloid progenitor) –> (IL-3 + GM-CSF + M-CSF) (monocyte) –> (GM-CSF + M-CSF) (macrophage)
Dendritic cells role (myeloid)
Classical - process and present foreign protein antigens to T cells
Follicular dendritic cells
passively present foreign antigen in form of immune complexes to B cells in lymphoid follicles
DCs differentiation
IL3 + GM-CSF (myeloid pro) –> M-CSF –> GM-CSF + IL-4
NK cells role
REcognize damaged cells by a deficiency in MHC antigens
Activated by IFNs
IL-12 and TNFa activate NK cells to secrete cytokines, INF gamma
NK cells differentiation
IL-7 (lymphoid progenitor) –> IL-2
important markers of NK cells
CD16 (FcgammaRIII) and CD56 (NCAM)
cytokines that activate NK cells
IFN
IL-12, TNFalpha
Severe congenital neutropenias
Many causes leading to a lack in the ability to produce or maintain a normal level of neutrophils
Leads to frequent bacterial infections
‘maturation arrest’ at the promyelocyte or myelocyte stage in the bone marrow
Chronic granulomatous disease
Inability to produce hydrogen peroxide and hypochlorous acid
Inability to kill phagocytosed bacteria
Chediak-Higashi Syndrome
Defect in gene LYST (CHS1), a lysosomal trafficking gene that affects lysosomes and melanosomes
Increased susceptibility to bacterial infections
Leukocyte adhesion deficiency
Lack of integrin subunit, the common β chain
Inability to recruit innate immune cells to site of inflammation
Increased susceptibility to bacterial, fungal, and viral infections.
What important products of complement activation are also chemotactic factors and what do they increase migration of
C3a, C4a, C5a ***
PMNs and macrophages
What important products of complement are deposited on surfaces with exposed amine or hydroxyl (ie bacteria)
C3b and C4b –> opsonins, further cleave C3
what’s C5b’s role in complement
bind microorganisms, act as focal point for membrane attack complex