Lecture 6

Question 1

What is major rule of antibody synthesis?

Answer 1

• Single B cell only makes one type of antibody
• Occurs by allelic exclusion
• Same is true for plasma cell
• Only one type of H chain and one type of L chain

Question 2

What has occured in ProB cell?

Answer 2

• Heavy DJ rearrangement

- No light chain rearrangement

Question 3

When does DJ rearrangement occur?

Answer 3

ProB stage

Question 4

What do mature B cells have on surface

Answer 4

IgM & IgD with same variable region

Question 5

What mediates VDJ rearrangement?

Answer 5

RSS

Question 6

What do RAG1/2 do?

Answer 6

Enzymes that recognize and align RSS and cleave sequence between

Question 7

Are all RAG rearrangements functional?

Answer 7

No

Question 8

How do IgM and IgD end up on same cell?

Answer 8

Alternative splicing of nuclear RNA

Question 9

What is junctional diversity?

Answer 9

• N region addition
• Nucleotides (B sequences) not present in germ line that are added to junctions of rearranged VDJ during rearrangement
• Adds to diverstiy

Question 10

What facilitates junctional diversity?

Answer 10

TdT

Question 11

3 contributions to Ig Diversity?

Answer 11

1. VDJ rearrangement
2. Junctional diversity
3. Combination of H & L chain

Question 12

What happens to non functional VDJ rearrangements?

Answer 12

They are deleted

Question 13

What happens to self reactive B cells?

Answer 13

1. Become anergic
2. Deletion
3. Rescued by receptor editing

Question 14

What happens to self reactive B cells?

Answer 14

1. Become anergic
2. Deletion
3. Rescued by receptor editing

Question 15

Where does isotype switching occur?

Answer 15

In periphery, not in marrow

Question 16

What causes isotype switching?

Answer 16

B cell interaction with antigen

Question 17

What can isotype switch result in?

Answer 17

IgG
IgE
IgA

Question 18

What is necessary for isotype switch?

Answer 18

• AID - Enzyme that will cleave loop
• Cleaved region is ligated associating VDJ region with new gene
• Cleaved region is deleted from genome

Question 19

Can B cell undergo multiple isotype switches?

Answer 19

Yes

Question 20

Where does generation of antibody diversity occur?

Answer 20

Generation of antibody diversity occurs in bone marrow in antigen independent manner

Question 21

What is hypermutation?

Answer 21

• Variable regions of Ig genes undergo BP mutation of 1/1000 when leave marrow
• Known as hypermutation as rates exponentially greater than what’s seen in normal cells
• Results in AA change in binding site changing its specificity
• This does not occur in the bone marrow and this IS in response to antigen

Question 22

Is hyermutation in response to antigen?

Answer 22

Yes

Question 23

What is an anegic cell?

Answer 23

• Non responsive, will not be activated when react with self
• This can happen to self reactive cells

Question 24

What is danger of anergic cells?

Answer 24

• Dangerous if become mutated and become activated

- Cause autoimmune disorders

Question 25

What is receptor editing?

Answer 25

- Rescues self reactive B cells by changing receptor - Instead of getting signal to die, RAG is upregulated allowing for another VJ rearrangement resulting in new B cell that is hopefully not self reactive

Question 26

What is receptor editing?

Answer 26

- Rescues self reactive B cells by changing receptor - Instead of getting signal to die, RAG is upregulated allowing for another VJ rearrangement resulting in new B cell that is hopefully not self reactive - Only happen on light chain

Question 27

Can receptor editing happen on heavy chain?

Answer 27

- Cannot happen on heavy chain as all the “D’s” were deleted in initial rearrangement - However, simply changing light chain changes specificity of receptor

Question 28

Which chain rearranged first?

Answer 28

Heavy

Question 29

Which chain rearranged first?

Answer 29

Heavy

Question 30

How many epitopes does T cell recognize?

Answer 30

Only one

Question 31

How many epitopes does T cell recognize?

Answer 31

Only one

Question 32

Chains on T cell?

Answer 32

- Alpha and Beta - Each chain has variable and constant region - Their variable regions come together to make binding site

Question 33

Is T & B cell concurrent in bone marrow?

Answer 33

No, T cells made in thymus

Question 34

T and B cell on same chromosomes?

Answer 34

Yes

Question 35

What are alpha and beta chains product of?

Answer 35

Alpha chain - product of V J rearrangement | Beta chain - product of VDJ rearrangement

Question 36

Do T cells demonstrate allelic exclusion?

Answer 36

Yes

Question 37

What mediates Rearragement in t cell?

Answer 37

Rag

Question 38

What ar TRECs?

Answer 38

- T cell rearrangement excision circles | - Intervening DNA that is removed and deleted in rearrangement

Question 39

How do you tell if patient is making Trecs?

Answer 39

See if they have TRECs

Question 40

Different in T & B cell formation?

Answer 40

- T cells do not display somatic hypermutation - T cells do not display isotype switch - T cells do not display differential splicing to get membrane & secreted form

Question 41

T/F: IG are encoded by gene segements on same chromosome?

Answer 41

False - Each family is on different chromosome

Question 42

T/F: one Ig can have two types of light chain

Answer 42

False

Question 43

T/F: myeloma proteins are result of polyclonal B cell activation

Answer 43

False

Question 44

T/F: In pre B cells both heavy and light chain genes are rearranged?

Answer 44

False

Question 45

When is hypermutation highly active?

Answer 45

Generation of memory B cells

Question 46

What has rearranged in Plasma Cell?

Answer 46

VDJ on one allele | VJ on other allele

Question 47

What has rearranged in Pre B lymphcyte?

Answer 47

No VJ DJ on one allele VDJ on other allele

Question 48

Main anitbody of primary response?

Answer 48

IGM

Question 49

Main antibody in secondary response?

Answer 49

- IGG | - IGG levels stay high longer here than IGM does in primary

Question 50

Explain secondary reagent?

Answer 50

- Inject Human IGG in animal and they make antibody it - Take human blood and mix with tetanus or something you were vaccinated for hoping that it will bind the antigen in tray - Take the animal generated antibodies to IGG and add them to tray and they should bind the human IGG - You label animal antibody with something you can detect - Secondary antibodies are directed against FC region of antibody