L17 effector cells

Question 1

what is clonal selection

Answer 1

selective expansion of lymphocytes that interact with antigen

Question 2

what are cytotoxic lymphocytes also known as

Answer 2

CD8 effector cells (T Cells) that have undergone proliferation and activation by a DC

Question 3

what are CTL used for

Answer 3

serial killers of tumour cells

they engage, disengage and continue to kill other cells

Question 4

how are proteins produced by viruses in infected cells displayed on MHC I

Answer 4

The proteins being made by the virus within the cell are sometimes released to the cytoplasm and loaded onto MHC

Question 5

where are CTL activated and by what

Answer 5

lymph or spleen

by a DC

Question 6

what are the ‘weapons’ of CTL

Answer 6

granzyme
perforin
CD95 ligand

Question 7

when are perforin and granzyme secreted by a CTL

Answer 7

when it recognises MHC peptide

Question 8

how does perforin work?

Answer 8

makes pores in the lipid bilayer by forming polymeric cylindrical structures allowing granzyme to enter the cell

Question 9

what does granzyme do

Answer 9

cleaves target cell proteins which initiates apoptosis

Question 10

what does CD95 ligand do?

Answer 10

bind to CD95 triggering apoptosis because enzymes like caspases are being activated which initiate apoptosis

Question 11

what attracts CTL to an area of the body

Answer 11

inflammation

Question 12

what happens during apoptosis

Answer 12

cell components are being degraded, doesn’t explode
uses energy
cell shrinks

Question 13

what happens to the fluid and membrane of cells during apoptosis

Answer 13

form apoptotic blebs

Question 14

what happens to apoptotic blebs

Answer 14

consumed and digested by macrophages or neutrophils (phagocytes)

Question 15

how do viruses downregulate MHC I

Answer 15

production of proteins which stop MHC reaching the surface

Question 16

what happens if a cell does not express or only has lo levels of MHC I

Answer 16

natural killer cells are activated

Question 17

What two receptors do NK cells use to activate apoptosis in infected cells

Answer 17

inhibiting

activating

Question 18

what does the activating receptor of NK cells do

Answer 18

binds to living cells and lets the NK know there is a cell there

Question 19

what does inhibitory receptor do

Answer 19

binds to MHC I

lets the NK know that the cell is expressing MHC I

Question 20

what does an NK do when there is no MHC

Answer 20

the activating receptor receives a positive signal and it builds up and it releases cell-killing proteins (perforin, granzyme)

Question 21

what happens during type 1 hypersensitivity

Answer 21

B cells are more prone to class switch to IgE

Question 21

what happens during type 1 hypersensitivity

Answer 21

B cells are more prone to class switch to IgE

Question 22

what happens during an allergic reaction

Answer 22

mast cells bind two IgE (that are sensitive to non-threatening antigen) antibodies to the surface through FC receptors
antigen crosslinks the antibodies which stimulate mast cells to produce histamines, serotonin (allergic mediators)

Question 23

what are Tregs

Answer 23

type of CD4 helper cells that secrete immunosuppressive cytokines

Question 24

what is peripheral tolerance

Answer 24

DC cells lacking CD80 which stops co-stimulation

Question 25

what happens during neonatal tolerance

Answer 25

a wave of Tregs is produced to suppress the cytokines
infants are already immunocompromised
central tolerance is highly active while neonatal

Question 26

what happens during central tolerance of B cells

Answer 26

self antigen is passed over maturing B cell in bone marrow