Lecture 4 - Antibodies and Antibody Diversity

Question 1

What is a complementarity-determining region (CDR)?

Answer 1

very genetically variable regions on both light and heavy chains that constitute the antigen-binding site of Ig

Question 2

Instructive Theory of antibody creation.

Answer 2

similar to making crowns. Cells respond to antigen by IMPRINTING the shapes of the antigen and make antibodies accordingly.

Not likely.

Question 3

Selective Theory of antibody creation.

Answer 3

antibodies are pre-made for everything we could possibly encounter. We don’t have enough genes for this theory to be possible!

Question 4

How many genes are needed to create all the antibodies in your body?

Answer 4

3

Question 5

Which Ig genes are in mature B cells?

Answer 5

mIgM and MIgD

Question 6

Describe a Pro-B gene (parent gene to a specific antibody)

Answer 6

Made up of V and C domains.

Has way too many stop codons. No gene product is made.

Question 7

Describe a B gene (that makes a specific antibody).

Answer 7

The stop codons from the Pro-B cell get deleted, and a specific antibody is made from the B gene that results.

Question 8

What is germ line DNA

Answer 8

DNA that is passed down through the gametes before it is modified by somatic recomination of maturation.

Question 9

Where is germ line DNA found?

Answer 9

Pro-B cells (bone marrow stem cells) contain germ line DNA

Question 10

What are the 4 mechanisms of antibody diversity?

Answer 10

1. No Ig production in Pro-B cells, only in B cells
2. Production of (kappa) chain protein
3. Production of (lambda) chain protein
4. Production of heavy chain protein
5. Recombinational Inaccuracy
6. N-nucleotide addition
7. Somatic mutation
8. Class Switching

Question 11

How does the production of the Kappa chain protein create antibody diversity?

Answer 11

During synthesis, only 1/30 V, 1/5 J, and 1C segment is randomly selected to be in the kappa chain out of many of these segments. Variability = 150

Question 12

How does the production of the LAMBDA chain protein create antibody diversity?

Answer 12

1/30 V, 1/7 J, 1/7 C

Variability = 210

Question 13

1/51 V, 1/30 D, 1/6 J

Variability = 9180

Answer 13

Diversity created by production of heavy chain protein.

Question 14

Which 3 genes do 2 x 10^6 antibodies come from?

Answer 14

kappa chain, lambda chain, heavy chain

Question 15

What is recombinational inaccuracy?

Answer 15

When V and J boxes are joined, they are recombined by enzymes in a different way for each B cell

Question 16

What is N-nucleotide addition?

Answer 16

Sometimes extra nucleotides are inserted between boxes when they are joined.

Question 17

What is somatic mutation?

Answer 17

VDJ genes in B cells can make single base changes (at CDR region) after antigen stimulation to create more affinity.

Question 18

What chains to T-cells have?

Answer 18

alpha and beta chains

Question 19

What is positive selection in the thymus?

Answer 19

If a T-cell has a moderate affinity to MHC, it is rescued from programmed cell death.

Question 20

What is LACK of positive selection in the thymus?

Answer 20

If a T-cell has no affinity for MHC, it undergoes apoptosis.

Question 21

What is negative selection in the thymus?

Answer 21

If a T-cell has a HIGH affinity for MHC, it undergoes apoptosis.