Atypical Immune Response Flashcards
Define sterilising immunity
An immune response which clears the infection completely using the innate and aquired immune system
Define non-sterilising immunity
A good immune response but fails to completely clear the infection, resulting in chronic infection
What is the human response to TB infection?
TB is inhaled and lodges in apex of lung
In 90-95% of individuals cell mediated immunity is crucial although non-sterilizing:
- Macrophages are key controlling cell
- T cell production of interferon gamma: activates macrophages
- Cytokine involvement
This TB can be reactivated and progress to cavitary TB
In 5-10% of individuals TB progresses directly to cavitary TB where TB is transmissable
How does TB bacteria avoid immune clearance?
Evolve to survive phagocytes:
- Alter constituents of phagosome so it is unable to fuse with lysosome
- Resists phagosome acidification by pumping out protons
- Releases proteins that reduces effect of lysosomal compounds
What is the human immune response to infection with HIV?
- Release of cytokines
- Antibody-virus complexes
- CD8+ cytotoxic T cells decrease viral load although this soon becomes ineffective
How does HIV avoid immune clearance?
Unable to make exact copies of itself/ regularly mutates. Mutants with selective advantage divide and replicate rapidly.
Accumulation of viral proteins focused on CD8 responnse makes then unrecognisable by CD4 cells rendering CD8 response ineffective.
What is the concept of immune enhancement of infection?
The immune response exacerbates the infection
How does Dengue virus exhibit the concept of immune enahancement of infection?
Different stereotypes of dengue.
Antibodies produced for one stereotype can help enhance the later infection by another sterotype leading to more severe and complicated dengue infection (DHV - dengue haemorrhagic fever with 2.5% mortality rate).
