failure's of the body's defenses Flashcards
______ are different strains of microorganisms that are antigenically distinct
serotypes
_______ is mutations in viral surface protein genes that lead to changes in viral surface antigens
antigenic drift
_______ is a process by which different strains of a virus combine to form a new virus having a mixture of the surface antigens of the original strain
antigenic shift
______ is when one copy of a gene is replaced by a different version
gene conversion
_____ is a viral state in which the virus has entered the cell but isn’t replicating
latency
______ is a bacterial protein that causes non-specific T cell activation by binding to MHCII and TCR
superantigen
______ is the phase of an infection when antibodies against a pathogen become detectable
seroconversion
name 5 mechanisms of immune system evasion by pathogens
genetic variation, mutations, gene conversion, latency, superantigens
how do pathogens evade host immunity by genetic variation
Ab responses only protect from infections by the same strain; pathogens exist as numerous strains/serotypes
streptococcus pneumoniae serotypes differ in ______
capsular polysaccharides
how does influenza use genetic variation to evade immunity
the different subtypes are based on hemagglutinin and neuraminidase
______ is error prone and generates point mutations
RNA polymerase/ RNA replication
point mutations in influenza lead to new viral strains that lack hemagglutinin or neuraminidase epitopes, causing antigenic _____
drift
antigenic ____ leads to emergence of a new virus with pandemic potential
shift
the trypanasome’s surface is formed of a _____
glycoprotein
the many different variants of glycoproteins are referred to as _____
variable surface glycoproteins (VSGs)
_____ allows for excision of VSG and replacement of VSG
gene conversion
how does gene conversion allow trypanasome evade host immunity
most trypanasomes express the same VSG, a minority express a different VSG. host makes Ab response to the dominant form, allowing the minority form to grow
to terminate viral infections, _____ are required to kill virus, which requires presentation of viral peptides on ____
CD8 T cells, MHC class I
how do cells use latency to evade host immunity
they do not replicate so few viral peptides are generated to present on MHC I, so no CD8 T cell cytotoxicity
______ are secreted by bacteria and stimulate a massive but ineffective T cell response
superantigens
describe the activation process of a superantigen
SAg binds to MHC II of APC. SAg engages TCR beta chain. SAg binds to CD28 costimulatory receptor.
