Recognition of infection Flashcards
what is CRP?
a marker for infection that is made by the liver
when does C3 bind to microbe membranes?
when the thioester domain in the alpha-domain of C3 is activated. The thioester domain is prevented from activation by the inhibitory beta-domain
how is the thioester domain in the alpha domain of C3 activated?
C3 removes the beta-chain that normally inhibits the thioester domain and exposes the highly reactive alpha-chain thioester domain
what is C3b and what is its function?
C3b is the active compliment molecule
- it immediately binds to adjacent microbes, or is inactivated by hydrolysis
what is the function of complement inhibitors?
prevent complement from binding and/or inactivate complement
what is caused by CD59 deficiency?
Paroxysmal nocturnal haemoglobinuria
- characterised by episodes of erythrocyte lysis
what is CD59?
a complement inhibitor expressed on host cells
what is the mechanism of CD59?
prevents final assembly of the membrane attack complex at the C8 to C9 stage
what are the features of Toll-like receptors?
recognize many types of pathogen molecules
-homologous to fruit fly toll receptor
- dimers with leucine-rich repeat (LRR) domains that bind PAMPs and DAMPs
how are gram positive and gram negative recognised differently by TLR?
gram-negative and gram-positive display different molecules for recognition by the innate immune system. While both types of membrane can be destroyed by lysozyme, we have different recognition systems for each class of bacteria
what detects gram-negative bacteria?
Gram-negative bacteria cell membranes contain lipopolysaccharide which is detected by TLR-4
what detects gram-positive bacteria?
Gram-positive bacteria have lipoteichoic acid (detected by TLR-2
what does TLR binding of PAMPs activate?
signalling pathways
what signalling pathways do PAMPs activate?
NF-kappaB transcription factor activation
Interferon regulating factor (IRF) pathways
MAP kinase pathway downstream transcription factors such as AP-1
what do TLRs recruit to their TIR domain?
different TLRs recruit different adapter proteins to their TIR domain