Exam 2- Immunity to Intracellular Pathogens

Question 1

what does it mean for an infectious agent to establish a focus of infection?

Answer 1

adheres to epithelial surface, the colonizes it or penetrates it to replicate in the tissues

Question 2

true/false: disease can only occur AFTER the infectious agent is not eliminated by innate immune response

Answer 2

true

Question 3

how do extracellular pathogens get around the body?

Answer 3

lymphatics or blood vessels

Question 4

how do intracellular pathogens get around the body?

Answer 4

direct transmission from one cell to another or release into the extracellular fluid and reinfection of adjacent and distant cells

Question 5

what is the principle mechanism of innate immunity against viruses?

Answer 5

type 1 interferons and NK cell-mediated killing of infected cells

Question 6

what do type 1 interferons (IFN-alpha and IFN-beta) do to protect against viruses?

Answer 6

cause neighboring cell to synthesize some enzymes to interfere with viral transcription and replication
“antiviral state”

Question 7

what receptors do NK cells have?

Answer 7

both activation and inhibition receptors

Question 8

when does the adaptive immune response against viruses begin?

Answer 8

day 4 until end of infection

Question 9

what mediates the adaptive immune response?

Answer 9

antibodies and cytotoxic lymphocytes

Question 10

what do antiviral antibodies function as?

Answer 10

neutralizing antibodies

Question 11

does IgM or IgG have a longer half life?

Answer 11

IgG

Question 12

true/false: influenza virus can evade innate immunity by mutating hemagluttinin antigen expressed on its surface

Answer 12

false: evading adaptive immunity

Question 13

what proves that cytotoxic lymphocytes are important with viral infections?

Answer 13

animals deficient in CD8+ T cells are more susceptible to viral infections

Question 14

how can viruses escape neutralization by pre-existing immunity?

Answer 14

point mutations (antigenic drift) and reassortment of RNA genomes (antigenic shift)

Question 15

how do viruses evade immune mechanisms in general?

Answer 15

antigenic variation
downregulation class I MHC molecules
produce immunosuppressive molecules
may infect and kill immunocompetent cells
equine herpes virus-1 (EHV-1): hides in trigeminal ganglion

Question 16

true/false: macrophages kill all bacteria

Answer 16

false: some can readily grow inside macrophages

Question 17

true/false: if a bacterial pathogen is present in the cytosol of a host cell, the infected cell is killed by cytotoxic T cells

Answer 17

true

Question 18

how do intracellular bacteria evade immune mechanisms?

Answer 18

blocking phagosome-lysosome fusion
disruption phagosome membrane and escape into cytoplasm
resistant cell wall

Question 19

how does neutralizing systemic viruses compare to neutralizing mucosal viruses?

Answer 19

systemic: IgG and IgM most important
mucosal: IgA plays a major role in blocking viruses from attaching with mucosal epithelial cells

Question 20

is complement a major part of defense against viruses?

Answer 20

no

Question 21

how does antibody-dependent cell-mediated cytotoxicity work?

Answer 21

mediated by natural killer cells
IgG coats virus infected cells and these get bound to NK cells through Fc receptors
NK cells destroy through perforin-dependent killing mechanisms

Question 22

what is the most important host defense after the virus infection has occured?

Answer 22

cytotoxic T lymphocyte response

Question 23

what is antigenic drift?

Answer 23

point mutations

Question 24

what is antigenic shift?

Answer 24

reassortment of RNA genomes

Question 25

what is antigenic variation?

Answer 25

viruses altering their genomes

Question 26

what allows influenza virus to survive in a population?

Answer 26

antigenic drift

Question 27

what cytokines do viruses encode molecules against?

Answer 27

IFN-gamma, TNF, IL-1, and chemokines

Question 28

do some viruses produce immunosuppressive cytokines?

Answer 28

yes

Question 29

what is protection against intracellular bacteria mediated by?

Answer 29

cytotoxic T lymphocyte and T helper cell responses