Lecture 5

Question 1

What encodes variable region of heavy chain?

Answer 1

V, D, & J genes

Question 2

What encodes light chain?

Answer 2

V & J

Question 3

How does VDJ gene varry in each cell?

Answer 3

• The organization of theses segments of the genes is the same in EVERY cell in the body EXCEPT the B/T cells in which they are rearranged allowing transcription

Question 4

What happens in B cell development?

Answer 4

• During B cell development DNA rearrangement must occur in which 1 V segment is placed next to one J segment
• Everything between the two that are combined is deleted from that B cells genome
• RNA will then be made, spliced, translated to get us to antibody

Question 5

Where does VDJ rearrangement occur?

Answer 5

Bone marrow

Question 6

Precursor to B cells?

Answer 6

HSC

Question 7

How many VDJ sements are there?

Answer 7

There are ~ 50 - 100 V gene segments
There are ~ 20 - 30 D gene segments
There are ~ 5 - 6 J gene segments

Question 8

What is purpose of VDJ rearrangement?

Answer 8

The creation of a highly specific antibody

Question 9

What is the order of the rearrangement?

Answer 9

• D if first moved by J then rearranged by V
  All intervening material is deleted
  The rearranged gene will end up close to the constant region

Question 10

Which antigens drive the rearrangement?

Answer 10

This is not antigen driven

Question 11

What is done in bone marrow transplant?

Answer 11

• Wipe out bone marrow and reconstitute it with HSCs

- CD34 + - the specific HSC that is used in bone marrow transplant

Question 12

Significance of CD34+

Answer 12

HSC used in bone marrow transplant

Question 13

What is the pro B cell?

Answer 13

• First stage in HSC development: HSC becomes pro B cell
• VDJ heavy chain rearrangement occurs here
• Once one allele rearranges, it wants to go to surface of cell so both heavy chains will be same

Question 14

When does VDJ rearrangement occur?

Answer 14

Pro B cell stage

Question 15

What is the Surrogate light chain?

Answer 15

• Binds to rearranged heavy chain and take it to surface of cell

Question 16

What happens when heavy chain makes it to surface?

Answer 16

Signal sent to cell to stop rearranging so both heavy chains will be the same

Question 17

What is the the pre B cell?

Answer 17

• What pro B cell becomes
• Turned off enzyme so heavy change no longer rearranged
• Enzyme will turn on again to rearrange light chain

Question 18

What characterizes immature B cell?

Answer 18

IgM on surface

Question 19

What do mature B cells do?

Answer 19

Immature B cells leave bone marrow to look for antigens to activate them

Question 20

What is on surface of mature B cells?

Answer 20

IgM & IgD

Question 21

What is true of IgM & IgD on matuer B cell?

Answer 21

• Variable region has same specificity

- Differnet antibodies however as constant region is not the same

Question 22

What is allelic exclusion?

Answer 22

• Rearrangement is only occuring on one allele and the other is turning off
• Prevents one cell from making more than one antibody

Question 23

What does allelic exclusion prevent?

Answer 23

B cell from having more than one antibody

Question 24

What is RSS?

Answer 24

• “Recombination signal sequence”

- Conserved sequence found upstream of V and downstream of J

Question 25

What is RAG?

Answer 25

- Recognizes RSS by V & J and cleave sequences between allowing V & J to come together to be ligated - The two RSS’s are coming together to ligate to each other

Question 26

What is BREC?

Answer 26

- “B cell recombination excision circle” | - Portion of gene between RRS segments that is cut out

Question 27

How do you tell if bone marrow transplant is taking?

Answer 27

- BRECs will be seen | - Signals that new B cells are being made

Question 28

What is difference between secreted and membrane IgMs?

Answer 28

- The difference is in the C terminal end that will or won’t sit in membrane - There will be a secreted or membrane portion on 3’ end of conserved area

Question 29

What determines if Ig is secreted or membrane?

Answer 29

Splicing

Question 30

What does IgD do?

Answer 30

- Noone really knows what IgD does, just know it is on surface of mature B cell

Question 31

What is the order of the rearrangement?

Answer 31

- D if first moved by J then rearranged by V - All intervening material is deleted - The rearranged gene will end up close to the constant region

Question 32

What does IgD do?

Answer 32

- Noone really knows what IgD does, just know it is on surface of mature B cell

Question 33

What is the light chain coded for?

Answer 33

Variable region - encoded for by V & J | Constant regoin - C exon

Question 34

How is heavy chain coded for?

Answer 34

Variable region - VDJ | Constant region - multiple C exons

Question 35

Where is c regoin found?

Answer 35

3' end of v genes

Question 36

First step in antibody creation?

Answer 36

Gene rearrangement

Question 37

What happens after V moved next to DJ?

Answer 37

All D segments 5' of rearrangment are deleted

Question 38

Which cells does VDJ rearrangement occur in?

Answer 38

Only those commited to becoming B lymphocytes

Question 39

What is predominant serum Ig?

Answer 39

IgG

Question 40

What is predominant secretory Ig?

Answer 40

IgA

Question 41

Most B lymphocutes have membrane Ig of what class?

Answer 41

IgD | IgM

Question 42

How much more IgM is there in serum than IgE?

Answer 42

1000x

Question 43

Antibody fragment with single comining site is designated?

Answer 43

Fab

Question 44

Ig classes can be distinguised base on?

Answer 44

Their heavy chains

Question 45

First step in rearrangement of heavy chain?

Answer 45

D brought next to J and stuff in between has been deleted

Question 46

What is Fab?

Answer 46

Variable region