Immune system in defence against infection Flashcards
describe how viruses evade the immune system?
viruses have rapid mutation rate as reverse transcriptase has a certain error rate should the proof reading fail to recognise the change this will lead to a mutation. This is very common as proof reading in RNA viruses is very poor
what is antigenic shift?
what impact does it have on infected individuals?
genetic rearrangement that can occur when they infect the same host.
means that those who has previously formed antibodies may no longer be protected due to expression of different haemagglutinin that may not be previously recognised by the antibodies that were formed against the previous strains, leading to pandemics, which is when a large portion of the population arent prepared with memory B cells to fight the infection
name 3 ways antibodies can defend the body against infection, describe one of them
opsonisation = Ab binds to epitope –> phagocytes bind to Fc portion to facilitate phagocytosis
neutralisation = Ab binds pathogen to prevent adherence and penetration of cells
complement activation = Ab binding Ag activates complement to opsonise target and lyse bacteria
What do cytotoxic T cell do?
recognise viral peptides presented by MHC 1, and kill cell if infected
how do macrophages destroy foreign material?
engulf foreign material by phagocytosis –> endosome formed joined with lysosome vesicle to form phagolysosome –> material digested –> digested material presented on cell surface using MHC 1/2
what are the 2 types of TLRs and what do they detect?
surface TLRs = bacterial antigens
internal TLRs = viral antigens/nucleic acid
how does the immune system act against helminths?
Th2 cells activate B cell production of IgE Abs –> recruit and activate eosinophils vie IL signalling -> mast cell recruitment also mediated by this –> specific IgE Abs aid mast cell to target helminth
