lecture 6 - B cell activation Flashcards

1
Q

activated can become what two cells

A

plasma or memory cells

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2
Q

plasma cells release their

A

BCR

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3
Q

roles of antibodies:
1. neutralisation

A

antibodies bind to the pathogen preventing it from affecting our cells

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4
Q
  1. opsonization
A

antibodies bind to pathogen and promotes phagocytes to engulf it

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5
Q
  1. activates the complement system
A

enhances opsonization and puts hole in pathogens

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6
Q

naive B cells express which BCRs

A

IgM or IgD

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7
Q

BCR binding to an antigen provides

A

signal 1 to a B cell

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8
Q

Igα and Igβ have what motifs in its cytoplasmic regions

A

ITAM (immunoreceptor tyrosine-based activation motif)

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9
Q

CD3 also has ITAMS. ITAMs have what residues

A

tyrosine

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10
Q

it is likely that the antigen is coated in what

A

complement

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11
Q

the complement can interact with what

A

Complement recepto3 3 on b cell surface

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12
Q

if this happens theres a bigger signal, why?

A

becuase you get a signal from the BCR and the CR2

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13
Q

thymus-independent antigens:
signal 2 is provided by

A

the antigen itself or extensive cross linking

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14
Q

thymus dependent antigen:
signal 2 is provided by

A

CD4 t cells

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15
Q

thymus independent antigens lead to which antibody production

A

only IgM (never class switches)

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16
Q

TI-1 antigens provide the second signal by

A

binding to other receptors on the b cells

17
Q

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

A

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

18
Q

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

A

CD40/CD40-L interaction

19
Q

why can all classes antibodies be produced from an TD antigen

A

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

20
Q

CD40-L is on the

21
Q

CD40 is on the

22
Q

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

A

physically linked

23
Q

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

A

the peptide added and the antigen
this called a conjugate vaccine

24
Q

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

A

germinal centres (GC)

25
B cells divide rapidly to become
centroblasts
26
centroblasts undergo
somatic hypermutation (due to AID increasing or decreasing its affinity) causing isotype switching
27
they then stop dividing and get smaller and these are called
centrocytes
28
once the B cell has its second signal from the t cell it enters the
b cell follicle
29
the dark zone is where?
the B cells are rapidly proliferating
30
some centrocytes move out of dark zone to the
light zone
31
follicular dendritic cells are in the light zone and the have antigen on their surface.
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
32
what region does the somatic mutation
V region
33
T fh cells help the B cells can secrete Th1 and Th2 type
cytokines
34
CD40 signal induces what
isotype switching
35
AID also tells the b cell to start breaking its DNA to put the hyper mutated VDJ with
a different constant region so the b cell changes from IgM/D to IgG,A or E
36
cytokines from T fh cell tells b cell which isotype to become