4. Antibody structure, diversity and antigen recognition

Question 1

in which region of the Ab does it exhibit Ag specificity?

Answer 1

Variable

Question 2

how many hyper-variable regions in heavy and light chains each?

Answer 2

3

Question 3

CDR?

Answer 3

complementatory determining regions

Question 4

what are the CDRs?

Answer 4

1,2 and 3

Question 5

what do the CDRs make up?

Answer 5

paratope of ab

Question 6

in what 3 ways are the CDRs complementary to the antigen?

Answer 6

shape
hydrophobiciity
charge

Question 7

what does an Ig domain consist of?

Answer 7

1 polypeptide chain folded into:

• 2 x anti-parallel beta-pleated sheets
• intra-chain disulphide bond

Question 8

function of hinge region on Ab?

Answer 8

allows each Ab binding site to act independently

Question 9

what mechanism allows many Ab to be produced from a small number of genes?

Answer 9

somatic recombination

Question 10

Describe process of formation of constant region of heavy chain

Answer 10

1. DNA - intron, exon, hinge region
2. transcription creates RNA
3. RNA splicing creates mRNA
4. Translation creates constant region of heavy chain

Question 11

Describe process of formation of variable region of heavy chain

Answer 11

1. Germline DNA = V, D, J and constant region with introns in between
2. somatic recombination 3 x
   a) move DJ together
   b) move VDJ together
   c) Move VDJ to join constant region
3. transcription to form RNA
4. RNA splicing to form mRNA
5. translation to form polypeptide chain

Question 12

Describe process of formation of variable region of light chain

Answer 12

same as heavy chain V region - no D fragment

Question 13

how many different types of V regions for heavy chain?

Answer 13

40

Question 14

how many different types of D regions for heavy chain?

Answer 14

25

Question 15

how many different types of J regions for heavy chain?

Answer 15

6

Question 16

What codes for most of the 3rd hypervariable region? why?

Answer 16

V and D regions - there are the most of these

Question 17

on the DNA - what is the L region?

Answer 17

Leader region - used to target polypeptide into the endoplasmic reticulum during synthesis

Question 18

What occurs in RNA splicing?

Answer 18

intron/exon RNA sequences are removed

Question 19

what segment codes for CDR1?

Answer 19

V

Question 20

what segment codes for CDR2?

Answer 20

V

Question 21

what segment codes for CDR3?

Answer 21

VDJ - hypervariable

Question 22

how is variation of Ab added for light variable chains?

Answer 22

2 types of light chain - kappa and lambda

Question 23

2 types of junctional diversity?

Answer 23

1. during recombination - exons remove AA

2. Terminal deoxyribonucleotidyl transferase (TDT) adds random nucleotides to VDJ segments

Question 24

during class switching, which part of the Ab changes?

Answer 24

constant region

Question 25

which 2 enzymes are involved in class switching from IgM to IgA?

Answer 25

AID - activation induced deaminase

UDG - uracil -DNA glycosylase

Question 26

what does AID do?

Answer 26

during somatic recombination - converts cytosine to uracil

Question 27

what does UDG do?

Answer 27

repairs mismatched bases C-G and U-A

Question 28

what occurs to Ag-Ab affinity over an immune response?

Answer 28

the affinity increases

Question 29

how does Ag-Ab affinity increase over time?

Answer 29

somatic hypermutation in variable regions - mutations in the AID and UDG

Question 30

for Ab with high Ag affinity, do they have a high or low dissociation constant? (Kd)

Answer 30

low

Question 31

what occurs to affinity when the concentration of Ag decreases?

Answer 31

only mutated B cells which produce high affinity Ab are stimulated

Question 32

what does isotypic mean?

Answer 32

variations of heavy and light chain in an Ab

Question 33

what does allotypic mean?

Answer 33

genetic allele differences intraspecies

Question 34

what does idiotypic mean?

Answer 34

variations of paratopes in Ab

Question 35

different types of non-covalent forces between Ab and Ag?

Answer 35

1. electrostatic
2. VDW
3. hydrogen bonding
4. hydrophobic

Question 36

what is the valence of an Ab?

Answer 36

number of binding sites for Ag on a Ab