Host defense

Question 1

bile destroys what type of virus?

Answer 1

enveloped viruses

Question 2

innate immunity against viruses consists of what cell types / molecules?

Answer 2

interferon alpha and beta (type I interferon)
NK cells
macrophages

Question 3

what is the other name of interferon type II?

Answer 3

IFNy

Question 4

most viruses stimulate production of IFNa and IFNb by what type of host cells?

Answer 4

INFECTED host cells

Question 5

how do IFNa and IFNb protect against viral infection?

Answer 5

inhibits viral replication in surrounding UNINFECTED hose cells

Question 6

leukocytes produce which IFN?

Answer 6

alpha

Question 7

what cell types produce INFb?

Answer 7

fibroblasts and other non-leukocytes

Question 8

what cell types produce IFNa?

Answer 8

leukocytes

Question 9

fibroblasts produce which IFN?

Answer 9

beta

Question 10

once type I IFN binds to receptor, which two pathways can be taken? what is the end result?

Answer 10

1. 2’-5’-oligoadenylate synthetase - degrades mRNA
2. dsRNA-dependent protein kinase - inactivates eIF2

inhibition of protein synthesis and interruption of virus replication

Question 11

what cell type is the first line of defense against virus-infected cells?

Answer 11

NK cells

Question 12

viruses downregulate which class of MHC? why? which cell type is ‘released from inhibition’ in response to decreased MHC?

Answer 12

class I MHC 
avoid lysis by CTLs 

NK cells

Question 13

NK cell activity is enhanced by what compound?

Answer 13

IFN

Question 14

ADCC

Answer 14

antibody dependent cell mediated cytotoxicity

Question 15

what are the specific roles of NK cells (3)?

Answer 15

mediate ADCC
crosslinking of IgG Fc receptors
apoptosis and perforin mediated osmotic death

Question 16

what are two antiviral products of macrophages? what do they do?

Answer 16

production of TNFa and NO - interfere with replication

Question 17

which has a longer duration of humoral response to viral infection - serum or mucosa?

Answer 17

serum

Question 18

what are the functions of antibodies (4)?

Answer 18

1. prevent virus from binding target host cell
2. opsonize virus to enhance phagocytosis
3. activate complement to lyse viral envelopes
4. facilitate ADCC by NK cells to lyse infected host cells

Question 19

what cell type represents the principal protective immunity during ESTABLISHED virus infections?

Answer 19

CD8+ CTLs (adaptive cell mediated immunity)

Question 20

is innate immunity effective against intracellular bacteria?

Answer 20

no

Question 21

how are NK cells responsible for killing intracellular bacteria?

Answer 21

• NK cells activated by macrophage-produced IL-12
• NK cells then produce IFNy
• IFNy activates macrophages to become more efficient killers

Question 22

what is required for full eradication of intracellular bacteria?

Answer 22

adaptive immunity

Question 23

how does adaptive immunity deal with intracellular bacteria?

Answer 23

mediated by a DTH-like reaction

1. T cells become activated - IFNy - activated macrophages eliminate bacteria
2. some mycobacteria may persist in body for extended periods - granuloma formation

Question 24

which IL steers immunity response toward Th2 immunity (antibody formation)?

Answer 24

IL-4

Question 25

what is the mycobacterium strategy for evasion of immunity?

Answer 25

inhibits fusion of phagolysosome

Question 26

what is the listeria monocytogenes strategy for evasion of immunity?

Answer 26

disrupts phagosome of macrophages and escapes into cytosol

Question 27

what are the roles of IFN alpha and beta?

Answer 27

• induce resistance to viral replication in all cells
• increase MHC I expression and antigen presentation in all cells
• activate dendritic cells and macrophages
• activate NK cells to kill virus infected cells

Question 28

how are bacteria that escape phagolysosomes into the cytosol killed?

Answer 28

bacterial peptides will be processed / expressed on class I MHC to activate CTLs

Question 29

what type of immunity do you get with lepromatous leprosy?

Answer 29

Th 2 mediated (antibodies - but they are not very effective)

Question 30

what type of immunity do you get with tuberculoid leprosy?

Answer 30

Th 1 mediated - granuloma formation