027 How microbes avoid the immune system Flashcards
How does H.influenze avoid complements?
It has a C5peptidase that will prevent MAC formation
How does S.pyogenes avoid complements?
Its M protein will bind to the H factor which prevents C4b formation causing complement cascade.
How are trypanosomes able to avoid the immune system?
Antigenic variation. They can also escape the phagosome
How is CMV able to avoid the immune system?
Concealment in areas that are immunologically privileged.
How does the microbe for the plague resist phagocytosis?
Yersinia pestis - It contains a virulon plasmid cell that encodes for an injectosome. This penetrates the macrophages and prevents the phagocytic action. It also blocks opsonisation and signalling.
How do Staphylococci and Streptococci avoid phagocytosis?
Thick capsule wall
S. aureus also secretes protein A, which binds to the Fc region. Hence, antibodies become functionally impaired.
How do Legionella pneumophilia avoid phagocytosis?
Forms a protein channel and injects many proteins that block lysosome fusion.
How does Herpes simplex avoid phagocytosis?
Similar to the protein A action of S.aureus.
How does Hep B evade the immune system?
Inhibits cytokine production
How do M.tuberculosis avoid phagocytosis?
M.tuberculosis prevents fusion with lysosome and also causes acidification of the lyosome.
How do Leishmania and Trypanosome avoid phagocytosis?
They just escape the phagosome.
How does the EBV evade immune system?
Produce homologue of immunosuppressive cytokine e.g. IL10
What ways can microbes prevent the presentation of antigen fragments on APC?
Blocking TAP which transports peptides into the ER. Binding to MHC class I, keeping it in the ER.
