4- Antibody Structure and B cell Diversity

Question 1

How many different kinds of Ag’s can an Ab bind to?

Answer 1

Just 1

Question 2

What is are the constant and variable regions called of the light chain Fab part of the Ab?

Answer 2

CL (Constant Light) and VL (Variable Light)

Question 3

What is the constant part of the heavy chain called in the Fc region?

Answer 3

CH (Constant Heavy)

Question 4

What are the hypervariable regions of the Ab?

Answer 4

They are the different amino acid composition of the variable regions of the variable domains.

Question 5

What are hypervariable regions also called? Why?

Answer 5

Complementarity-determining Regions (CDR’s) because they bind complementary Ag’s.

Question 6

What are the antigenic determinants/epitopes?

Answer 6

They are the part of the Ag that the Ab bins to.

Question 7

What is formed between the VH and VL chains to bind the Ag?

Answer 7

Deep pocket

Question 8

What is the linear epitope?

Answer 8

Ab’s bind to several adjacent sugars and use shallower clefts

Question 9

What is a discontinuous epitope?

Answer 9

When a protein folds, it binds well to an Ab

Question 10

What type of chemical bond is formed between the Ag and Ab?

Answer 10

Noncovalent forces

Question 11

How are monoclonal Ab’s used clinically?

Answer 11

They’re used to block T cell responses and prevent rejection of transplants.

Question 12

What condition is monoclonal Ab’s used to treat?

Answer 12

Non-Hodgkin B cell lymphomas

Question 13

What does cytometry analyze?

Answer 13

Cell populations and the size of cell populations (like the amt of B or T cells)

Question 14

What is added to the 1 dimensional cytometry plot?

Answer 14

monoclonal Ab

Question 15

When an anti-TCR monoclonal Ab is added to a blood solution for a 1 dimensional cytometry analysis, what peaks occur?

Answer 15

1 peak for the lymphocytes that do not bind the Ab (everything except T cells) and the 2nd peak for the T cells that bind the Ab

Question 16

What is used for the 2 dimensional cytometry plot?

Answer 16

2 monoclonal Ab’s

Question 17

What happens when you add a anti-TCR and anti-IgM monoclonal Ab to a blood solution for a 2 dimensional cytometry analysis?

Answer 17

It splits up into 4 quadrants, sepatating the B cells (binding to anti-IgM) from the T cells (bind the anti-TCR) from cells that dont bind either (like NK) and from cells that bind both TCR and IgM (which are no cells)

Question 18

How is the V (variable) region of the light chain made?

Answer 18

It’s made by the combination of one V and one J (joining) segment.

Question 19

How is the V chain of the heavy chain made?

Answer 19

It’s encoded by 1 V, 1 D (diversity), and 1 J segment.

Question 20

How is the C (constant) of the light and heavy chains made?

Answer 20

By 1 C gene. That’s it.

Question 21

How do the variable regions of the light chain form by somatic recombination?

Answer 21

V and J are cut and spliced together on rearranged DNA

Question 22

How do the variable regions of the heavy chains form by somatic recombination?

Answer 22

The D first forms the J (DJ) and then the DJ joins the V region to form the rearranged DNA.

Question 23

What is the recombination signal sequence (RSS)?

Answer 23

They are genetic sequences that cut and rejoin DNA during somatic recombination to make sure that the gene segments are joined in the correct order.

Question 24

What are the set of enzymes that are needed to recombine V, D and J segments?

Answer 24

V(D)J recombinase

Question 25

Where is V(D)J recombinase found?

Answer 25

Lymphocytes

Question 26

What are the complement proteins for V(D)J recombinase?

Answer 26

Recombination Activating Gene-1 and 2 (RAG-1 and RAG-2)

Question 27

What would happen if there was a defect in V(D)J recombinase?

Answer 27

The B cells couldn't create Ab's --> severe immune system defects.

Question 28

What does the enzyme Terminal deoxynucleotidyl transferase (TdT) do?

Answer 28

It adds random nucleosides to the DNA to diversify the Ab variable region.

Question 29

What is the process of junctional diversity?

Answer 29

It contributes P and N nucleotides which adds to the diversity in the 3rd hypervariable region between the D and J segment.

Question 30

How is the IgM and IgD produced in the naive B cell?

Answer 30

By differential splicing of the same primary RNA transcript

Question 31

What is allelic exclusion?

Answer 31

It means that Ig gene rearrangement is tightly controlled so that only 1 heavy chain and 1 light chain are produced.

Question 32

What is the function of the B-cell receptor (BCR)?

Answer 32

It binds a specific antigen and passes it signal inside to cause the B cell to divide and differentiate

Question 33

What is the function of Ig α and Ig β?

Answer 33

They tell the intracellular proteins to have the B cell divide and differentiate.

Question 34

How does a B cell begin to produce secreted Ab's rather than BCR's?

Answer 34

When an Ag binds to the BCR it signals the B cell to secrete Ab's that bind to the same sequence of the Ag.

Question 35

What is somatic hypermutation?

Answer 35

It's the point mutations throughout the rearranged V regions of the heavy and light chain genes.

Question 36

What is affinity maturation?

Answer 36

It's the increasing affinity of Ab's for the infecting pathogen as somatic hypermutation occurs.

Question 37

What shape is the IgM on the B cell?

Answer 37

Monomeric- Y shaped

Question 38

What shape is the secreted IgM?

Answer 38

Pentamer

Question 39

What occurs during isotype switching?

Answer 39

In proliferating B cells, there can be recombination of the C genes that enables the rearranged V region to be used with other heavy C chains.

Question 40

What 2 Ab's have subtypes?

Answer 40

IgG (1-4) and IgA (1&2)

Question 41

Which Ab is high in the mucosa?

Answer 41

IgA

Question 42

Which Ab is highest in the serum?

Answer 42

IgG1

Question 43

Which Ab is produced in the primary immune response?

Answer 43

IgM

Question 44

Which Ab is produced in the secondary immune response?

Answer 44

IgG

Question 45

Which Ab forms a dimer?

Answer 45

IgA

Question 46

How is the IgA dimer formed?

Answer 46

It's formed by 2 monomers being joined by a J chain

Question 47

Where is the dimeric IgA found?

Answer 47

Mainly in the lymphoid tissue under mucosal surfaces and in secretions like milk, saliva, sweat and tears.