Assignment 6

Question 1

what do NK cell arise from

Answer 1

bone marrow precursors (lymphoid progenitor cells)

Question 2

where are NK cells found

Answer 2

blood, spleen, peritoneal exudate

Question 3

role of NK during a CD4+ Thp cell activation

Answer 3

NK cell which is activated by IL-12 secretes IFNγ which influences the Th0 differentiation primarily to a Th1 subset

Question 4

role of NK cells in viral infection and cancer

Answer 4

kill autologous cells that are virally infected or infected with cancer by releasing its granules perforin and granzyme and escaping the region so as not to be affected by the toxic effects of the released granules

Question 5

what cytokine is released when NK cells are stimulated with IL-12

Answer 5

IFNγ

Question 6

role of IL-15, and IL-18 when NK cells are stimulated with IL- 12

Answer 6

they enhance IFNγ induced by IL-12

Question 7

source of IL-12, IL-15, IL-18

Answer 7

dendritic cells and macrophages

Question 8

role that interferon gamma (IFNγ) plays in the differentiation of Th0 cells to CD4+ T cells

Answer 8

it influences Th0 differentiation primarily to a Th1 subset

Question 9

how are lymphokine activated killer (LAK) cells generated and what is its unique property

Answer 9

in the presence of high concentration IL-2, NK cells differentiate to LAK cells which are potent killers of tumor cells

Question 10

NK cells express activating and inhibitory receptors that interact DIRECTLY with ligands on the target cell. What are the three classes of ligands for these receptors?

Answer 10

specific self - Class I MHC
MHC Class-I like molecules
molecules unrelated to MHC

Question 11

“stress- induced” ligand that allows NK cells to destroy target despite normal expression of Class I MHC

Answer 11

MICA (MHC Class I chain related gene A)

Question 12

three conditions in which MICA is upregulated

Answer 12

on virally infected cells, cancer cells,

Stress :)

Question 13

three conditions in which Class I MHC decreases on target cell

Answer 13

stress, some viral infections, some tumors

Question 14

two cytokines whose interaction with target cells leads to upregulation of Class I MHC

Answer 14

IFNγ (Type 2 interferon) or IFNα/β (Type 1 interferons)

Question 15

source of IFNγ, IFNα, IFNβ

Answer 15

IFNγ - CD4+ Th1 cells, NK cells
IFNα - virally infected leukocytes
IFNβ - virally infected fibroblasts

Question 16

how does the balance of activating and inhibitory receptors on the NK cell determines the fate of the target cell

Answer 16

if the inhibitory receptor on NK cells is strong enough, the cell expressing Class I MHC is protected and the cell tolerance is maintained

if the activating receptor on NK cells is stronger, the cell will not be protected and will be destroyed

Question 17

why does NK cells not destroy host cells in the absence of infection or tumors

Answer 17

infections and tumors decrease the amount of self Class I MHC-self peptide expression which makes it impossible for NK inhibitory receptors to deliver inhibitory signals because of insufficient self Class I MHC-self peptide so activating receptor takes over and cell is destroyed

without infection and tumors, there is a sufficient amount of self Class I MHC-self peptide so inhibitory receptor can deliver its signal hence protecting the cell

Question 18

two molecules that are released from the granules extruded by NK cells (NK cell armamentarium)

Answer 18

granzymes

perforin

Question 19

immune processes that led to the binding of Fcγ to the target cell

Answer 19

it recognizes Fc region of antibodies so if there is an antibody present on a target cell then Fcγ will bind to it

Question 20

how are target cells killed when Fcγ binds to it

Answer 20

there is a release of perforin and granzymes which destroys the target cell

Question 21

why are NK cell not destroyed itself in the process of killing a target cell

Answer 21

granules polarize to the conjugation region and is released in a way that allows the NK cells to escape the harmful effects of granzymes and perforin

Question 22

why is the Fcγ-FcγR mode of recognition for target cell destruction referred to as “antibody-dependent cell mediated toxicity” (ADCC)

Answer 22

because different antibodies recognize different viral proteins embedded in the cell membrane of the infected cell and then kill the infected cell