failure's of the body's defenses

Question 1

______ are different strains of microorganisms that are antigenically distinct

Answer 1

serotypes

Question 2

_______ is mutations in viral surface protein genes that lead to changes in viral surface antigens

Answer 2

antigenic drift

Question 3

_______ 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

Answer 3

antigenic shift

Question 4

______ is when one copy of a gene is replaced by a different version

Answer 4

gene conversion

Question 5

_____ is a viral state in which the virus has entered the cell but isn’t replicating

Answer 5

latency

Question 6

______ is a bacterial protein that causes non-specific T cell activation by binding to MHCII and TCR

Answer 6

superantigen

Question 7

______ is the phase of an infection when antibodies against a pathogen become detectable

Answer 7

seroconversion

Question 8

name 5 mechanisms of immune system evasion by pathogens

Answer 8

genetic variation, mutations, gene conversion, latency, superantigens

Question 9

how do pathogens evade host immunity by genetic variation

Answer 9

Ab responses only protect from infections by the same strain; pathogens exist as numerous strains/serotypes

Question 10

streptococcus pneumoniae serotypes differ in ______

Answer 10

capsular polysaccharides

Question 11

how does influenza use genetic variation to evade immunity

Answer 11

the different subtypes are based on hemagglutinin and neuraminidase

Question 12

______ is error prone and generates point mutations

Answer 12

RNA polymerase/ RNA replication

Question 13

point mutations in influenza lead to new viral strains that lack hemagglutinin or neuraminidase epitopes, causing antigenic _____

Answer 13

drift

Question 14

antigenic ____ leads to emergence of a new virus with pandemic potential

Answer 14

shift

Question 15

the trypanasome’s surface is formed of a _____

Answer 15

glycoprotein

Question 16

the many different variants of glycoproteins are referred to as _____

Answer 16

variable surface glycoproteins (VSGs)

Question 17

_____ allows for excision of VSG and replacement of VSG

Answer 17

gene conversion

Question 18

how does gene conversion allow trypanasome evade host immunity

Answer 18

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

Question 19

to terminate viral infections, _____ are required to kill virus, which requires presentation of viral peptides on ____

Answer 19

CD8 T cells, MHC class I

Question 20

how do cells use latency to evade host immunity

Answer 20

they do not replicate so few viral peptides are generated to present on MHC I, so no CD8 T cell cytotoxicity

Question 21

______ are secreted by bacteria and stimulate a massive but ineffective T cell response

Answer 21

superantigens

Question 22

describe the activation process of a superantigen

Answer 22

SAg binds to MHC II of APC. SAg engages TCR beta chain. SAg binds to CD28 costimulatory receptor.