Immune Evasion Flashcards
What does pathogen opsonisation lead to?
Gradient of C3a, C5a and bacterial proteins
C5a binds to C5aR and C3a binds to C3aR which causes expression of ICAM and then neutrophil extravasation
How does a bacterial capsule aid opsonisation evasion?
Polysaccharide hides antigenic structures
How does SpA aid opsonisation evasion?
Binds to antibodies via their Fc region
How does SSL10 aid opsonisation evasion?
Secreted protein that binds to Fc region which prevents Fc receptors on neutrophils from detecting antibodies on the surface of bacteria
How do proteases aid opsonisation evasion?
They degrade antibodies
4 stages of the complement cascade?
- Initiation
- Formation of C3 convertase, C4 + C2
- Formation of C5 convertase
- MAC formation
How does SCIN aid complement opsonisation evasion?
Binds to C3bBb to inhibit formation of C3 and C5 convertases
How does Efb protein aid complement opsonisation evasion?
Binds to C3d in C3 to induce conformational change which prevents binding of factor B to C3 and C3dgto CR2. Results in lower phagocytic recognition
How does SSL7 protein aid complement opsonisation evasion?
Binds to C5 which prevents it from being converted to C5a and b for MAC formation
How do proteases and Factor H aid complement opsonisation evasion?
Cleave and inactivate complement components or acquire host-derived complement regulators
How do CHIPS proteins aid evasion of neutrophil functions?
Bind to C5aR and FPR1 to reduce neutrophil migration
How do FLIPr and SSL5 aid evasion of neutrophil functions?
Bind to Fc y and Fc a receptors respectively
How do toxins aid evasion of neutrophil functions?
Kill neutrophils
How do interferons work?
Produced by virally infected cells when something goes wrong, e.g double stranded RNA
Secreted and bind to other cells to initiate antiviral state- transcription of genes and activation of NK cells
