3 - Innate 1: Barrier Flashcards
Which cells secrete host defence peptides?
Epithelial cells
Macrophages
Neutrophils
Generally, what are host defence peptides, how long are they and what do they do to microbial membranes?
Small cationic peptides (29-42 amino acids), they cause cell lysis which due to osmotic imbalance.
What are the two host defence peptides and what are they structurally composed of?
Defensins (beta sheet peptides)
Cathelicidins (alpha helix)
Name two categories of molecules recognized by pattern recognition receptors (PRRs)
PAMP
DAMP
PAMP stands for
conserved pathogen associated molecular pattern
DAMP stands for
Damage-associated molecular patterns
Where are PAMPS found? (type of organism)
On microbes (exclusively)
What are DAMPS associated with/where are they found?
Aging, dead, or damaged self structures
What are PAMPS? Name 2 examples.
In simple terms: a pathogenic marker specific to non-self microbes.
In more complicated terms: an exogenous compound found on lower micro-organisms composed of sugars, proteins, and lipids/nucleic acids. The DNA that codes these compounds belongs to a part of the genome that is an evolutionarily conserved molecular motif.
Examples: peptidoglycan, flagella, gram negative LPS, Gram positive teichoic acid, unmethylated CpG dinucleotides, dsRNA, fungal chitin or zymosan
What do you call: a pathogenic marker specific to non-self microbes.
In more complicated terms: an exogenous compound found on lower micro-organisms composed of sugars, proteins, and lipids/nucleic acids. The DNA that codes these compounds belongs to a part of the genome that is an evolutionarily conserved molecular motif.
PAMP
What are DAMPS? Give two examples.
Endogenous self components released by dead/dying cells or damaged tissues.
Examples:
Structures usually sequestered or exist in different forms (uric acid, DNA in the cytosol)
Wrong location. ATP or uric acid in extracellular space; extracellular cholesterol, hyaluronan, amyloid b when internalized.
Wrong quantity or combined with others. ATP
Two types of cell surface PRRs:
Toll like receptors (TLRs)
C-Type Lectin receptors (CLRs)
Two types of extracellular PRR’s:
- mannose-binding lectin/mannose-binding lectin (alternative C’ cascade)
- C-reactive protein (CRP) (binds to phosphocoline on microbes)
Two types of intracellular PRRs:
- Toll-like receptors 3, 7,8, & 9
- Nucleotide binding oligomerization domain (NOD) receptors. (NLRs)
Name 3 different adapter proteins involved in TLR-PRR signaling cascades.
NF-kb
IRF transcription factors
MAP kinase
What event does NF-kb transcription factors in TLR signalling lead to?
pro inflammatory cytokines/chemokines
What event does interferon regulating factor (IRF) transcription factors lead to in TLR signalling cascades?
Type I interferon dependent antiviral response
What is lectin?
A carbohydrate binding protein
What are the two broad categories of PRR’s (which are categorized on the basis of function)
Signaling PRRs and Phagocytic PRRs
What is inflammasome?
A signaling cascade that results in the massive production and secretion of IL-1B and IL-18 which are both potent proinflammatory cytokines
Which type of cells become activated by MAMPs (microbe associated molecular patterns) and DAMPs to synthesise and release mediators of inflammation?
Sentinel cells
What is NALP3/NLRP3?
The best studied inflammasome type: it is a large protein complex formed in macrophages following stimulation by a PAMP followed by the second signal provided by a DAMP (ATP, uric acid, alum). The end result is the activation of caspase 1 protease which cleaves IL1.IL-18 into active forms for release. Indicative of injury, metabolic stress, or environmental irritants.
The best studied inflammasome type: it is a large protein complex formed in macrophages following stimulation by a PAMP followed by the second signal provided by a DAMP (ATP, uric acid, alum). The end result is the activation of caspase 1 protease which cleaves IL1.IL-18 into active forms for release. Indicative of injury, metabolic stress, or environmental irritants.
NALP3/NLRP3
What does an inflammasome response suggest has happened to the host?
Microbial invasion and cellular damage have occured. We know this because for the inflammasome to be triggered it requires activation via both PAMP and DAMP.
3 steps in the inflammasome:
Pore formation
Disruption of lysosomes
Generation of ROS
What are cytokines?
Cytokines are proteins released by cells to communicate to other cells.
What are chemokines?
Chemokines are proteins released by activated macrophages to stimulate movement of leukocytes to the area.
What does TLR stand for?
toll like receptor
A family of structurally similar transmembrane proteins that detect a broad range of PAMPs derived from bacteria, viruses, fungi and protozoa. They were discovered through research into a similar receptor found in fruit flies.
TLRs
Toll like receptor
What is the difference in methylation of mammalian DNA and prokaryotic DNA?
Mammalian DNA can be methylated but prokaryote DNA is not.
Even though there are variations in TLRs (most mammals encode about 13), they are still well conserved. Describe the basic structural components of a TLR
- C-terminus: Cytosolic TIR domain - in charge of signaling adapter molecules to initiate signal cascade.
- N-terminus: horseshoe shaped recognition domain - for recognizing PAMP or DAMP. has lots of leucine repeats.
- Transmembrane: 20 uncharged, mainly hydrophobic residues.
True or False: TLR’s can be found on extracellular and intracellular surfaces?
True. some TLR’s will be located on the membranes of endosomes which recognize endosomal PAMPS (unfortunately this means cytosolic invaders are not detected by the TLRs within the cell because their recognition domain will be facing the side inside the endosome)
What PRR is important in recognizing cytosolic PAMPS?
NLRs
=NOD-like receptors = nucleotide-binding and oligomerization domain-like receptors
Are NLR’s present on any type of membrane?
No they float in the cytosol
What do NLRs detect?
Intracellular dangers (ligands from cellular damage, infection internalized by endocytosis
Once activated by a PAMP or DAMP, what does the NLR activate?
cell death and inflammation
Name two DAMPS
serum amyloid a (SAA)
DNA
ATP
Uric acid
An adapter protein involved in TLR signaling cascade which stimulates inflammatory cytokines/chemokine release
NF-kB transcription factors
An adapter protein involved in TLR signaling cascade which stimulates type 1 interferon (IFN)-dependent antiviral response
Interferon regulating factor (IRF) transcription factors
An adapter protein involved in TLR signaling cascade which stimulates downstream transcription factors, e.g. AP-1
MAP Kinase
An cell surface and phagocytic PRR that recognizing cell wall component sugar/polysaccharides of bacteria/fungi/yeast e.g. lectin.
CLR = c type lectin receptor
Anatomical/physiological barrier of the upper respiratory tract
Trapping and removing particulates in mucus
Anatomical/physiological barrier of the trachea/bronchi
mucus
cilia mediated clearance
cough
Anatomical/physiological barrier of the mammary gland
Keratin plug
flushing
complement
lysozyme
lactoferrin
lactoperoxidase
Anatomical/physiological barrier of the reproductive tract
low pH
Anatomical/physiological barrier of the skin
keratin barrier
desiccation (removal of moisture)
desquamation
low pH due to fatty acids
Anatomical/physiological barrier of the intestinal tract
rapid changes in pH
lysozyme
defensins
hydrolases
bile acids
peristalsis
mucus
