3 - Pattern Recognition Receptors - Angyal Flashcards
What are PAMPs? and give 2 examples
Pathogen Associated Molecular Patterns
- differ from self cells
- critical to the survival/function of the pathogen therefore cannot differ too much and will most always be recognised by innate cels
- shared by many microbes
- eg lipoteichoic acid - G+ve, LPS G-ve
What are DAMPs?
Damage Associated Molecular Patterns
- host-derived molecules indicative of infection, stress, transformation, cellular damage
What are the 4 receptors of the innate immune system and describe v briefly what they do?
cytoplasmic signalling receptors, membrane-bound phagocytic, membrane-bound signalling, soluble receptor
- job is to recognise conserved/relatively invariant patterns frequently found on pathogenic surfaces
Give examples of PAMPs for bacteria, viruses, fungi and protozoa
Bacteria; G+ve lipoteichoic acid, G-ve LPS, flagellin (normally monomeric broken down version), unmethylated CpG DNA, N-formylated proteins (fMLP)
Viruses; dsRNA
Protozoa; mannose rich glycans, GPI-linked proteins
Fungi; B-glycan, chitin
Give some examples of DAMPs
- mitochondrial components (should be in mitochondria)
- DNA (should be in nucleus)
- phosphatidylserine. normally kept on intracellular side of membrane by flippases. when cell undergoes apoptosis flippases stop working, PS can then be released -> extracellular side
- HMGB1 (high mobility group box 1 proteins), histones that should be bound to DNA but found in cytoplasm
- uric acid - indicative of kidney damage, oxidative stress
- heat shock proteins - eg Hsp70 responds under stress
Are PRRs expressed exclusively by cells of innate immune system?
NO PRRs expressed by both immune and non immune cells (encoded for by germline)
Give the 4 types of PRR and give examples of each
- soluble receptors (complement, ficolins, MBL)
- membrane bound phagocytic (complement, mannose receptors, scavenger)
- membrane bound signalling (scavenger, TLR4)
- cytoplasmic signalling (NOD-like, TLR7/8)
What do soluble receptors recognise?
DAMPs - altered self/non self molecular patterns
What is efferocytosis and why is it important that it is done?
soluble receptors are important opsonins that aid the clearance of apoptic cells. prevents inflammation being induced in tissue when not needed
What are NETs and name 2 soluble receptors that recognise these?
NETs - released genomial, mitochondrial DNA
recognised by collectins , ficolins
What is the long name for collectins?
collagenous lectin-binding proteins
What is the structure of a collectin?
collagen domain and a Ca2+ binding domain
Describe the 2 types of collectin proteins from the lecture
SP-A. expressed by lung alveolar macrophages that can bind to and aid clearance of pathogens
SP-D binds to genomic DNA/phospholipids and Abs and can also aid in the clearance of pathogens
Describe the 3 types of membrane - bound phagocytic receptors and
- scavenger receptors. recognise anionic polymers, acetylated LDL eg CD14 recognises LPS, CD36 -> LDL
- complement receptors
- C-type lectins eg macrophage mannose receptors
What type of receptor (of the 4 described) are chemotactic receptors on phagocytes?
membrane-bound signalling