🌞 Pathogen Recognition by Innate Immunity Flashcards
(17 cards)
What are pattern recognition receptors (PRRs)?
Soluble or membrane bound
Recog pamps/damps
What are pathogen-associated molecular patterns (PAMPs)?
Molecular patterns produced by pathogen activity
What are the main types of PRRs in the innate immune system?
- Mannose receptors
- Scavenger receptors
- C-type lectin-like receptors
- Toll-like receptors (TLRs)
- Cytoplasmic receptors (NOD-like [NLRs], RIG-I-like [RLRs])
What is the role of Toll-like receptors (TLRs)?
Membrane bound on various ICs
Trigger intracell signalling pathways - mount ir
Detetc various PAMPs e.g. TLR4 - gram -ve bact LPS
What are the locations of different TLRs (cell surface vs endosomal)?
Expressed on MPs + DCs
- Surface: TLR2, TLR4, TLR5, TLR6
- Endosomal: TLR3, TLR7, TLR8, TLR9
What does TLR4 detect?
Bacterial LPS
What do TLR3, TLR7, and TLR9 detect?
DsRNA, ssRNA, CpG dna
What are C-type lectin receptors and what do they bind?
PRRs on myeloid cells e.g. MPs, DCs
Bind carb structures on microbes
What are scavenger receptors and what do they detect?
PRRs on myeloid cells e.g. MPs, DCs
Bind a wide range of ligands → modified self (e.g. oxidised LDL) & microbial components (e.g. bact CW components)
What are NOD-like receptors (NLRs) and what do they detect?
Soluble prrs
Detect pamps/damps in cytosol e.g path components escaped from phagosome
What are RIG-I-like receptors (RLRs) and what do they detect?
Sluble PRR
Detects intracellular pathogens in cytoplasm - specifically CYTOPLASMIC VIRAL RNAo
What are soluble PRRs and where are they found?
Collectins & defensins
Found in bloodstream/serum
What are collectins and what do they bind?
C-type lectins w collagen domains → bind carb strucs on MO surfaces
Soluble PRR → in bloodstream
What is mannose-binding lectin (MBL) and how does it contribute to immunity?
Type of collectin
Binds repetitive carb structures (e.g., mannans) on microbes → Activates complement → opsonisationy
What types of molecules are considered DAMPs (damage-associated molecular patterns)?
• Intracellular proteins released by damaged cells → e.g. HMGB1, heat-shock proteins
• Mitochondrial components → e.g. mtDNA, formyl peptides
• Metabol ites & ions → e.g. ATP, uric acid, potassium
• ECM fragments → e.g. hyaluronan, heparan sulfate
How do PRRs distinguish self from non-self?
PAMPs/DAMPs → molecular patterns not typically found on healthy host cells
• Self-cells lack pathogen-specific structures → e.g. LPSs, unmethylated CpG DNA
• PRRs localized to avoid reacting with host molecules → e.g. TLRs in endosomes detect viral RNA
What are defensins and what do they bind?
Soluble PRR → in bloodstream
Sml cationic antimicrobial peptides
Bind microbial membranes → attracted to negative charges (e.g. phospholipids in bacterial membranes) → Disrupt membrane integrity → form pores → lysis
Alpha and beta types (conserved across species)
