Immune Evasion Flashcards
Bacteria complement evasion
Degrade C3
S.aureus : Aur
S.pyogenes: SpeB
Bacteria complement evasion.
What inhibit complement convertases?
S.aureus : SCIN
Bind to 3bBb
Bacteria complement evasion
Recruit negative regulators
S.aureus: Sbi
S.pyogenes: M protein/protein H
Both recruit factor H (on bacteria surface)- inactivate C3b
What does pathogen recognition receptors do?
Directly detects microbes/microbial products
What detects conserved microbial structure
TLR receptors
What detects microbial carbohydrate
CLEC receptor
What detects formylated peptides
FPR receptors
How immune receptors indirectly detect bacteria
-Microbes opsonised by antibody/complement.
-Detected by Neutrophils through Fc/complement receptors
What is Activator receptor
Enhances immune cell activity
How does s.aureus inhibit chemotaxis and activation
CHIPs- binds to C5aR
Prevents binding of C5a.
Neutrophils does not migrate to site of infection and not activated though c5aR
How does s.pyogenes inhibit chemotaxis
SpyCEP - cleaves CXCL8 and prevents binding to CXCR1/2
Neutrophils do not migrate to sites of infection and do not become activated through CXCR1/2
S.aureus. What blocks Fc receptor?
FLIPr binds to Fc Y receptor (IgG) preventing detection of IgG opsonised bacteria-> reduce antibody mediated phagocytosis and killing of s.aureus.
SSL5 inhibits Fc a receptor (IgA).
Bacteria can kill neutrophils:
With toxins- fewer neutrophils at side of infection- reduce phagocytosis and killing of s.aureus/s.pyogenes
