escape strategies Flashcards
what are the 6 types of escape strategies
Hiding, interfering, destroying, virulence factors, mutations, disrupting
describe the hiding cell escape strategy
hides from the immune system by residing within cells
can lay dormant for years
individual will be asymptomatic
will emerge once resistance is lowered
example = HPV
describe the interfering cell escape strategy
they interfere with the function of the immune system by blocking signals
example = anthrax
secretes 3 different proteins (protective antigen, lethal factor and oedema)
supresses pro-inflammatory cytokine secretion which prevents the inflammatory response
describe the destroying cell escape strategy
they destroy elements of the immune system (e.g. APC peptides)
example = small pox
-secretes proteins which inhibit complement enzymes
- which interferes with MHC class 1 proteins
describe the virulence factors cell escape strategy
they use virulence factors to destroy or cause malfunction of host cells.
example = chlamydia trachomatis
- doesn’t need to invade host cell, instead secretes toxins and virulence factors
- these make influence membrane channels and deliver anti-host factors into the cell
- which leads to apoptosis (cell death)
describe the mutations cell escape strategy and the 2 types
they generate escape mutations to avoid being a target of cytotoxic t cells
Antigenic drift and antigenic drift
what is antigenic drift
point mutation in genes code for immunogenic glycoproteins on the surface of the virus - leads to change in presentation - lack of recognition from the body
describe the disrupting cell escape strategy
they disrupt complement pathways, phagocytosis, innate immune receptors and adaptive immune response
what is antigenic shift
the alteration of the surface of an antigen by combining 2 different strains - leads to different presentation
what is a virulence factor
molecules or traits that help pathogens infect or damage their hosts
what is an example of a virulence factor a pathogen could adapt to avoid phagocytosis
A capsule around its self - this creates a larger SA making it more difficult to be engulfed and recognised
how does Yersinia spp use virulence factors to cause immunosuppression
it secretes virulence antigen LcrV
- this then signals to TLR2 dependant signalling to stimulate IL-10 secretion
- this leads to immunosuppression as IL-10 is an anti-inflammatory cytokine inhibiting the activity of NK cells and macrophages impeding immunopathology
what are the multiple escape mechanisms of HIV
hiding
hijacking through immunosuppression - they replicate in CD4+ cells leading to cell death
- this degrades the hosts ability to mount a strong cell mediated response
- it also increases the body’s susceptibility to other infections
Destruction - targets C type lectin on dendric cells to skew the T cell response
how does tumour evasion work
they avoid recognition by masking their antigens with a thick outer coat
- increase Treg counts to counteract an immune response
- secrete factors to promote angiogenesis to improve circulation and enhance tumour growth
- has a high rate of genetic mutation and deletion
why do tumours secrete TGF-B during evasion
to inhibit the proliferation of lymphocytes
