Immunity Against Infection III Flashcards
What are the 4 evasion mechanisms of pathogens
Concealment of antigens
Antigenic variation
Immunosuppression
Interference with effectors
Which viruses conceal antigens through stopping MHC I presentation
Herpes simplex virus (cold sore)
What other 2 ways can antigen concealment occur
Privileged sites
Uptake of host molecules to disguise foreign recognition
Which virus lays dormant in the cns privileged site until times of stress etc
Herpes zoster virus (chicken pox/shingles)
Give an example of uptake of host molecules to conceal antigens
Schistosomes parasites will remove molecules off cells so they aren’t recognised
Which pathogen has 23 varied antigens / polysaccharides causing evading mechanisms
Streptococcus
What are the 2 strep vaccines
Pneumovax- uses ti 2 response to release antibodies via 23 different polysaccharide antibodies
Prevnar 13- conjugates polysaccharide with diphtheria toxoid for a TD response
Why isn’t pneumovax effective in kids
Don’t have a ti 2 response in b cells so can’t produce antibodies for the streptococcus polysaccharide ag
Antigenic drift and shift eg in influenza is another type of antigen variation causing evasion. Explain difference
Drift is a slight mutation in hemagluttinin and neuraminidase
Shift is where two diff animal strains eg pig and bird exchange rna.
Both Can’t be recognised by antibodies at all so can’t stop influenza entrance
Which parasite can gene switch antigen for evasion mechanism
Trypanosomes (cause African sleeping sickness)
What antigen is genetically rearranged and unrecognisable by antibodies in trypanosoma
Vsg
Variant specific glycoprotein
How does hiv cause immunosuppression (3rd evasion mechanism)
Attacks CD4, macrophages and dendrites
Which 2 pathogens cause increased t reg stimulated immunosuppression (t regs stops th1 and th2 and immunity)
H pylori (surface bacteria)
Leishmania (ic parasite)
What is the marker for t reg levels when detecting h pylori and leishmania
Cd25 and CD4
How do measles cause immunosuppression
Infect dendritic cells (stop T cell stimulation) (by stopping MHC I and II)
Prevent il 12 release (stops th1 response and nk)
How do strep and neisseria interfere with evading mechanism to adhere to epithelial surfaces
They contain iga proteases. Degrades iga so they can adhere to surfaces
How does staphylococcus interfere with antibodies
Staphylococcus protein A binds to fc portion of antibodies
Causes antibodies to not activate complement / opsonisation
Which virus interferes with complement and inhibits it
Small pox/vaccinia
Which parasite prevents c3a and c5a via interfering with complement
Pseudomonas
Which cytokine can smallpox interfere with and inhibit
Ifn y- stops th1 response eg macrophages,CD8 and NK
Which virus can produce its own suppressive il10 cytokine (usually from t regs)
Epstein Barr
How does mycobacterium interfere with effector mechanism
Stops phagocytosis via stopping phagosome and lysosome fusion
What is pathology through innate and adaptive responses called
Immunopathology
How does lps binding to tlr4 in innate cause systemic issues
Causes macrophage to release cytokines like il 1, tnf a
These cause fever, endotoxic shock, cytokine storm of systemic inflammation, causes dic, drop in circulation by increasing vascular permeability to cause inflammation
How is granulomas an example of immunopathology
Macrophages aggregate in response to mycobacterium tb and leprae
Causes necrosis in cell
What immunopathology causes skin rashes in measles
T cells activation
How can antibodies to strep protein be an issue / immunopathology
They can attack heart muscle to cause rheumatic fever
How does Ebola interfere with effector mechanisms / cause immunosuppression
Infect dendrites and macrophages, T cells and NK cells
Dendrites and macrophages can’t present MHC
Also interferes with type 1 ifn
