how microbes avoid immune system

Question 1

how does yersinia pestis avoid immune system

Answer 1

• yersinia plasmid codes for injectisome
• injectisome punches a hole in membrane of target cell
• this allow infiltration of yop protein
• this cuases actin depolymerisation and inhibition of signal transduction
• inhibits phagocytosis

Question 2

how does stapylococcus aureus avoid immune system

Answer 2

• A proteins bind to antibodys
• prevent antibodys opsonising microbes
• inhibits phagocytosis

Question 3

what are three ways microbes can avoid innate immunity

Answer 3

• avoiding/ inhibiting phagocytosis
• avoiding complement
• avoiding cytokines

Question 4

how does mouse pox avoid cytokines

Answer 4

• produces soluble protein which can bind to cytokines
• this prevents cytokine binding to its receptor
• to combat this we can give antibodies which can bind to the soluble protein produced by the virus, this allows the cytokine to bind to its receptor

Question 5

what are the 3 mechanisms microbes can avoid the adaptive immune system

Answer 5

• antigenic variation
• antigen shift/drift
• active supression

Question 6

what is active supression

Answer 6

• certain microbes such as viruses can prevent MHC presentation
• e.g herpes simple virus has an immediate early gene which codes for a protein that binds to TAP and prevents entry of peptides in endoplasmic reticulum
• adenovirus- binds to mhc and retains it in the endoplasmic reticulum prevents mhc presentation

Question 7

how does trypanosoma brucei avoid immune system

Answer 7

• has surface variant glycoproteins on its surface
• over 1600 genes which codes for these variant surface glycoproteins
• only present one of these glycoproteins at a given time
• when host produces antibodies to the variant surface glycoprotein the parasite can change it to another type of variant surface gylcoprotein making the antibody incompatible

Question 8

how does influenza avoid the host immune system

Answer 8

• antigenic drift- mutations
  -antigenic shift- gene reassortment giving rise to new strains of the influenza- happens upon co-infection of two influenza strains to one host cell
• which is why new flu vaccines arise each year

Question 9

how does hiv avoid immune system

Answer 9

• antigenic drift- mutations result new strains of HIV to arise
• which is why its hard to develop a vaccine for HIV

Question 10

how does microbes avoid the complement

Answer 10

• capsule can inhibit binding of complement