lecture 6 - B cell activation

Question 1

activated can become what two cells

Answer 1

plasma or memory cells

Question 2

plasma cells release their

Answer 2

BCR

Question 3

roles of antibodies:
1. neutralisation

Answer 3

antibodies bind to the pathogen preventing it from affecting our cells

Question 4

2. opsonization

Answer 4

antibodies bind to pathogen and promotes phagocytes to engulf it

Question 5

3. activates the complement system

Answer 5

enhances opsonization and puts hole in pathogens

Question 6

naive B cells express which BCRs

Answer 6

IgM or IgD

Question 7

BCR binding to an antigen provides

Answer 7

signal 1 to a B cell

Question 8

Igα and Igβ have what motifs in its cytoplasmic regions

Answer 8

ITAM (immunoreceptor tyrosine-based activation motif)

Question 9

CD3 also has ITAMS. ITAMs have what residues

Answer 9

tyrosine

Question 10

it is likely that the antigen is coated in what

Answer 10

complement

Question 11

the complement can interact with what

Answer 11

Complement recepto3 3 on b cell surface

Question 12

if this happens theres a bigger signal, why?

Answer 12

becuase you get a signal from the BCR and the CR2

Question 13

thymus-independent antigens:
signal 2 is provided by

Answer 13

the antigen itself or extensive cross linking

Question 14

thymus dependent antigen:
signal 2 is provided by

Answer 14

CD4 t cells

Question 15

thymus independent antigens lead to which antibody production

Answer 15

only IgM (never class switches)

Question 16

TI-1 antigens provide the second signal by

Answer 16

binding to other receptors on the b cells

Question 17

TI-2 antigens contain repeated epitopes and they will do what

Answer 17

cross-link many BCR on the same B cell surface
this massively amplifies signal 1 (doesnt give a signal 2)

Question 18

thymus dependent antigens:
BCR binds antigen (signal 1) and it then internalises the antigen and presents it on MHC class II to the CD4 T cells and receives signal 2 by

Answer 18

CD40/CD40-L interaction

Question 19

why can all classes antibodies be produced from an TD antigen

Answer 19

because cytokines secreted by T cell help b cell to class switch

Question 20

CD40-L is on the

Answer 20

T cell

Question 21

CD40 is on the

Answer 21

B cell

Question 22

epitopes recognised by the antibody and the T cell are different but they are

Answer 22

physically linked

Question 23

how to convert a TI antigen to a TD antigen:
add a protein to the polysaccharide, the antigen will be internalised and peptides presented will include

Answer 23

the peptide added and the antigen
this called a conjugate vaccine

Question 24

inside B cell follicles, B cells are rapidly proliferating in the

Answer 24

germinal centres (GC)

Question 25

B cells divide rapidly to become

Answer 25

centroblasts

Question 26

centroblasts undergo

Answer 26

somatic hypermutation (due to AID increasing or decreasing its affinity) causing isotype switching

Question 27

they then stop dividing and get smaller and these are called

Answer 27

centrocytes

Question 28

once the B cell has its second signal from the t cell it enters the

Answer 28

b cell follicle

Question 29

the dark zone is where?

Answer 29

the B cells are rapidly proliferating

Question 30

some centrocytes move out of dark zone to the

Answer 30

light zone

Question 31

follicular dendritic cells are in the light zone and the have antigen on their surface.

Answer 31

some t cells become T fh cells and they will follow the b cell into the light zone
the centrocytes will take up the antigen from the FDC if its affinity has improved after somatic hypermutation and present it to the T fh cell and the Tfh selects the B cells with the best BCR and the Tfh helps the b cells become memory and plasma cells
ones with decreased affinity to the antigen undergo apoptosis or go back into the dark zone and try again

Question 32

what region does the somatic mutation

Answer 32

V region

Question 33

T fh cells help the B cells can secrete Th1 and Th2 type

Answer 33

cytokines

Question 34

CD40 signal induces what

Answer 34

isotype switching

Question 35

AID also tells the b cell to start breaking its DNA to put the hyper mutated VDJ with

Answer 35

a different constant region so the b cell changes from IgM/D to IgG,A or E

Question 36

cytokines from T fh cell tells b cell which isotype to become