L2 Immune recognition

Question 1

what are the two types of recognition molecules

Answer 1

B cells (B cell receptor/immunoglobulin)
T cells (TCR)

Question 2

what is the B cell immunoglobulin structure

Answer 2

2 heavy 2 light chains, constant and variable domains at the two combining site - antigen binding
Hinge

Question 3

how come B cell immunoglobulins move to bind to target

Answer 3

have a hinge

Question 4

what is the T cell receptor structure

Answer 4

Alpha and beta chain has constant (close to cell surface) and variable domain – only one antigen combining site made of variable alpha and beta chain

Question 5

what is the difference between B and T cell recognition

Answer 5

T cell cant directly recognise need info presented to them via antigen presenting cell

Question 6

how do B cells recognise

Answer 6

surface Ig – bind directly to pathogen /antigen

Question 7

what happens to B cell following recognition

Answer 7

B cell activated makes plasma cells = lots more Ig which all bind to the pathogen

Question 8

how do T cells recognise

Answer 8

needs info of pathogen processed and presented to it via MHC
antigen presenting cells do this e.g. dendritic cells

Question 9

what happens to T cell following recognition

Answer 9

effector cell activated – might be CD4 or CD8 (depends on the MHC)

Question 10

where is there variability the variable domains

Answer 10

areas of hypervariability – variation between amino acid structure is huge = will recognise a different target
3 areas of hypervariability in heavy and light

Question 11

how are B cells activated

Answer 11

only through B cell clustering

Ig alpha and Ig beta have capacity to signal to cell to become activated – have tyrosine receptor molecules to intracellulary activate Ig alpha and beta molecules found in conjunction with B cell receptor

Question 12

why cant the B cell become activated by itself

Answer 12

might be a chance encounter with antigen or might bind to a target not specifically – can’t have this or adaptive response and B cells constantly activated

Question 13

what does BCR complex clustering cause

Answer 13

lots of B cells bind to target = B cell receptor clustering

turns on Ig alpha and beta signal B cell to start making lots of antibodies

Question 14

what is the BCR co-receptor complex

Answer 14

second signal through complement receptors binding to complement that has opsonized the pathogen

Question 15

what is needed for B cell to make antibodies

Answer 15

BCR clustering and BCR co-receptor complex

Question 16

what is the TCR for

Answer 16

not able to signal only there for indirect recognition via antigen presenting cell

Question 17

what are the two classes of TCR

Answer 17

alpha beta

gamma delta

Question 18

what are the T cell co-receptors

Answer 18

CD$

CD8

Question 19

what is the structure of the CD4 receptor

Answer 19

one chain

Question 20

what is the structure of the CD8 receptor

Answer 20

one alpha one beta molecule in separate chains

Question 21

what does the helper T cell express

Answer 21

helper T cell expresses CD4 alongside T cell receptor

Question 22

what does the cytotoxic T cell express

Answer 22

cytotoxic T cell expresses CD8 alongside T cell receptor

Question 23

what does MHC class I present to

Answer 23

CD8

Question 24

what does MHC class II present to

Answer 24

CD4

Question 25

when does the T cell kill the pathogen

Answer 25

virus gone into the cell on its own *infected will be in cytosol virally infected cell T cell by MHC I – bind to CD8 co receptor T cell – to kill it

Question 26

when is the T helper cell activated

Answer 26

pathogen deliberately taken into cell via phagocytosis will be in vesicle T cell with CD4 co receptor will bind = helper T cell activated to help clear it

Question 27

what can MHCI present

Answer 27

small peptides 8-10 amino acids to CD8 cell

Question 28

what can MHCII present

Answer 28

larger at least 13 amino acid epitope to CD4

Question 29

what is the CD3 complex function

Answer 29

has activation motifs inside cell that activate T cell to carry out its effector function

Question 30

what is the CD3 co-receptor function

Answer 30

CD3 and co-receptor complex comes together to signal and activate the T cell

Question 31

where are cytosolic pathogens degraded

Answer 31

cytosol

Question 32

what peptides bind to a cytosolic pathogen

Answer 32

MHCI

Question 33

what T cell are cytosolic pathogens presented to

Answer 33

CD8

Question 34

what happens to cytosolic pathogens

Answer 34

killed - cell death

Question 35

where are intravesicular pathogens degraded in

Answer 35

endocytic vesicles

Question 36

what peptides bind to intravesicular pathogens

Answer 36

MHCII

Question 37

what T cell are intravesicular pathogens presented to

Answer 37

CD4

Question 38

what happens to intravesicular pathogens

Answer 38

activation to kill intravesicular bacteria and parasites

Question 39

where are extracellular pathogens and toxins degraded

Answer 39

endocytic vesicles

Question 40

which peptides bind to extracellular pathogens and toxins

Answer 40

MHCII

Question 41

what are extracellular pathogens and toxins presented to

Answer 41

CD4

Question 42

what happens to extracellular pathogens and toxins

Answer 42

activation of B cells to secrete Ig - eliminate them

Question 43

why do other non innate cells have MHCI

Answer 43

any cell could be infected by virus so not just innate cells with MHC I

Question 44

what happens in MHCI processing and presentation

Answer 44

proteasome degrades antigen in cytosol – pieces taken to endoplasmic reticulum MHCI load info onto cell surface = activate CD8 cytotoxic T cell phagocytosis - degraded in vesicle

Question 45

where is MHCII made

Answer 45

made in endoplasmic reticulum

Question 46

what happens to MHCII invariant chain

Answer 46

has an invariant chain bound to it, when leaves endoplasmic reticulum is cleaved in vesicle

Question 47

what is important in blood transfusion

Answer 47

need to have HLA matching in transplantation