B Cells

Question 1

What do B cells look like under the microscope?

Answer 1

Identical to T cells

Question 2

Where are B cells produced?

Answer 2

Bone marrow

Question 3

What do B cells have on their surface?5

Answer 3

Transmembrane BCR
IG alpha and beta
CD 19
CD20
CD40

Question 4

Where do secreted antibodies come from?

Answer 4

Plasma cells

Question 5

What are Ig alpha and beta?

Answer 5

Aren’t immunoglobulins

Used to send message to lymphocyte when ab meets ag

Question 6

Markers for B cells

Answer 6

CD19 and CD40

Question 7

Which immunoglobulins do naive B cells make?

Answer 7

IgM and IgD

Question 8

2 regions of Ab- what do they do?

Answer 8

Variable and constant
Variable binds to Ag
Constant determines class of Ab

Question 9

What kind of Ag do Abs recognise?

Answer 9

Native Ag

Question 10

Structure of Ab:

Answer 10

2 identical heavy chains, 2 identical light chains
stretch of hydrophobic AA transmembrane
Short cytoplasmic chain

Question 11

How many classes of Ab are there? how are they different?

Answer 11

5 classes - dif constant region eg IgM - mue C region (heavy)
Light chain constant is kappa or lamda eg IgM can have either kappa or lamda

Question 12

Where does Ab variability come from? then?

Answer 12

Genetic recombination, then clonal selection

Question 13

What is clonal selection + 3 stages:

Answer 13

Ag selects most appropriate B cell

Selective activation, clonal proliferation, differentiation to plasma or memory

Question 14

What is somatic hypermutation?

Answer 14

Fine tunes Antibody - cells become quantitatively and qualitatively better during proliferation for secondary response

Question 15

When do B cells class switch? what classes are there?

Answer 15

Once stimulated by antigen. IgM, IgG, IgA, IgD, IgE

Question 16

How do B cells class switch?

Answer 16

Need help from Th2 cells - then mature to produce other classes

Question 17

Interaction between naive B cell and Th2 cell: 4

Answer 17

B7 (Bcell) - CD28 (Th2),
CD40 (B cell) to CD40L (Th2)
MHC B cell to TCR
exchange cytokines

Question 18

What does class of Ab depend on? example:

Answer 18

cytokines produced by Th2. eg IL4 and IL13 –> IgE

Question 19

What happens after class switching?

Answer 19

Ag induced proliferation and somatic hypermutation of the new class’s V region

Question 20

How do you get loads of mutations in somatic hypermutation?

Answer 20

No proofreading for V region, but regulatory regions that specify where to mutate

Question 21

Cost of somatic hypermutation?

Answer 21

Not always good, can be poor affinity, moderate or good

Question 22

What do you call it when there is even better binding after somatic hypermutation?

Answer 22

Affinity maturation

Question 23

What happens to the Ab with bad hypermutation?

Answer 23

Die

Question 24

Where does most of B cell proliferation happen?

Answer 24

secondary Lymph node

Question 25

How can B cells act as professional APCs?

Answer 25

They grab the Ab and Ag and take it in,
Show it to TCR of T cell using MHCII (B7, CD40)
cytokines activate T helper cell

Question 26

T cell independent Ags:

Answer 26

For some antigens - cross links so many so signal through Ig alpha and beta strong enough that no need for T cell help.
eg polysaccharides
Really good IgM but no class switching

Question 27

How do Ig alpha and beta work?

Answer 27

have tyrosines on ITAMS - tyrosine kinases add phosphate to tyrosines