B cell maturation and Ab synthesis

Question 1

List the steps of B cell maturation

Answer 1

Pro-B –> Pre-B —> B cell —> Plasma Cell

Question 2

During which stage of B cell maturation does D-J rearrangement for heavy chain occur

Answer 2

Pro-B cell (early stages of heavy chain production)

Question 3

During which stage of B cell maturation does V-DJ rearrangement for heavy chain occur?

Answer 3

Pre-B cell

Question 4

Which stage does initiation of light chain rearrangement occur?

Answer 4

Pre-B cell to B cell. Once light chain is synthesized, you have a B cell

Question 5

What stage of B cell maturation secrete antibodies?

Answer 5

Plasma cells

Question 6

Where does differentiation of B-cell occur?

Answer 6

in bone marrow

Question 7

Pre-B cell turns turns on a gene whose product is?

Answer 7

Surrogate light chain

Question 8

Accessory molecule (a fake light chain) that binds to cytoplasmic u heavy chain and brings a small amount to the surface

Answer 8

Surrogate light chain

Question 9

When the surrogate light chain brings a part of the heavy chain to the surface, what two important signals does it give off?

Answer 9

Tells cell to stop undergoing further V-DJ rearrangement and to start rearrangement of light chain

Question 10

Pre-B cell has what marker?

Answer 10

Cytoplasmic u heavy chain (recall that IgM is the only Ig present in immature B cell)

Question 11

Antibody synthesis is mediated by rearrangement of ____ to form functional Ig genes

Answer 11

Ig gene segments

Question 12

First stage of Ab synthesis

Answer 12

Rearrangement of heavy chain segments

Question 13

Heavy chain segments are made of the following gene segments:

Answer 13

Variable (V)
Diversity (D)
Joining (J)
Constant Region (C)

Question 14

VDJ rearrangement results in a functional _____

Answer 14

V region

Question 15

What does the functional V region (VDJ rearrangement) encode?

Answer 15

Heavy chain variable domain of the assembled antibody molecule

Question 16

After VDJ rearrangement, RNA synthesis of the rearranged ehavy chain gene is initiated and proceeds through which region gene segments?

Answer 16

C region

Question 17

What is the primary transcript processed into?

Answer 17

mRNA

Question 18

What is the mRNA then translated into?

Answer 18

IgM, D, G, A, or E, depending on the stage of B cell maturation and class switching

Question 19

Amount of V heavy chain domains (VH)

and V light chains

Answer 19

100 VH, 35 VL

Question 20

amount of D heavy chain domains and D light

Answer 20

27 DH, and 0 DL!

Question 21

Amount of J heavy chain domains and Jlight

Answer 21

6 JH, and 5 JL

Question 22

What is rearranged in light chain?

Answer 22

V-J

Question 23

After V-J rearrangement, RNA synthesis of the rarranged light chain gene is initiated and proceeds through the C region gene segments. This primary transcript is processed into what?

Answer 23

mRNA

Question 24

light chain mRNA is then translated into?

Answer 24

Kappa or lambda light chains

Question 25

Once the light chain and heavy chain synthesis have occured, an Ig is assembled where?

Answer 25

In B cell and transported to cell surface

Question 26

When does Ig convert from a membrane anchored form to a secreted form?

Answer 26

Upon differentiation of the B cell into a plasma cell

Question 27

What enzyme mediates the V-DJ rearrangement?

Answer 27

VDJ recombinase; it can cleave/ligate/correct DNA errors

Question 28

VDJ recombinases that are lymphoid specific (T cells and B cells)?

Answer 28

RAG1 and RAG2 = recombinase activating genes (need lymphoid specific so it doesn’t occur in…skin or kidney!)

Question 29

What ensures that you have correct rearrangement order of DJ and then V-DJ?

Answer 29

12-23 spacer rule

Question 30

What are the 5 molecule basis of Ig Diversity?

Answer 30

1. Multiple V region genes
2. Recombination of VJ and VDJ gene segments
3. Combinatorial association of H and L chains
4. Junctional Diversity
5. Somatic hypermutation

Question 31

How many multiple V region in heavy and light chains?

Answer 31

V heavy = 100

V light = 35

Question 32

How many recombination variations can you have for heavy chain VDJ and light chain VJ gene segments?

Answer 32

VDJ = 16,200 (100V*27D*6J)
VJ = 175 (35V * 5J)

Question 33

How many H and L combinatorial associations?

Answer 33

16,200 *175 = 2.836 x 10^6 different combinations

Question 34

When the gene segments come together during the rearrangement process but don’t combine faithfully

Answer 34

Junctional diversity

Question 35

This enzyme is shown during VDJ rearrangements in junctional diversity that adds nucleotides in a non-template driven fashion at DNA break points prior to ligation

Answer 35

terminal deoxynucleotidyl transferase

Question 36

Junctional sites on heavy and light chains

Answer 36

heavy chain : V and D, D and J

light chain: V and J

Question 37

When does somatic hypermutation take place?

Answer 37

After B cell engages antigen (antigen dependent)

Question 38

Antibodies mutate at a higher/lower rate than DNA in rest of genome

Answer 38

Higher rate. Particularly in the DNA coding the variable domains

Question 39

What are the two main things Somatic hypermutation contribute to?

Answer 39

1. affinity maturation

2. upregulates Activation Induced Cytodine Deaminase (AID)

Question 40

higher affinity antibodies will out-compete the lower affinity antibodies (higher affinity B cell will survive, lower affinity dies)

Answer 40

Affinity maturation

Question 41

This enzyme introduces mutations into the variable domains of Igs; contributes to converstions of nucleotides from DNA into RNA (by uridine) leading to affinity maturation

Answer 41

AID

Question 42

When does AID become activated?

Answer 42

When B cell is activated

Question 43

B cells undergo asymmetric division to form?

Answer 43

Memory B cells and plasma cells

Question 44

Circle of DNA consisting of everything between the “D3” and “JH4” connection (could be any one of the Ds with the Js in heavy chain)

Answer 44

Circular episome

Question 45

If you knock out RAG genes, what happens?

Answer 45

Severely compromise immune system

Question 46

2 antigen independent steps of antigen biosynthesis/modification

Answer 46

1. VDJ rearrangement

2. VJ rearrangemet

Question 47

Antigen dependent steps of antigen production

Answer 47

1. class switching

2. somatic hypermutation