Immunology 4

Question 1

What chromosomes in humans are the kappa and gamma light chains on?

Answer 1

Lamda -22

kappa - 2

Question 2

In humans what chromosome is the heavy chain on?

Answer 2

14

Question 3

What segments are the light chains encoded by in the genome?

Answer 3

V (variable) and J(junctional) gene segments

Question 4

What segments are the heavy chains encoded by in the genome?

Answer 4

V (variable), J (junctional) and D (diversity)

Question 5

What is combination diversity?

Answer 5

Generating variable region exons by recombining gene segments

Question 6

In heavy chain gene recombination which two segments join first.

Answer 6

DJ

followed by addition of V to make VDJ

Question 7

How many nucleotides are in the recombination signal sequences?

Answer 7

7 or 9 nucleotides that flak the gene segments

Question 8

How many nucleotides separate the flanking nucleotides around gene segments?

Answer 8

12 or 23

the 12 23 rule

Question 9

What does the RAG complex contain?

Answer 9

RAG1 and RAG2 and other enzymes

Question 10

Is the RAG complex expressed in

a) T cells
b) B cells
c) Both

Answer 10

both

Question 11

What is junctional diversity? and what causes it?

Answer 11

• Diversity in the junction between gene segments (DS cut is precise, the re joining is not)
• caused by RAG complex

Question 12

What adds palindromic nucleotides (p-nucleotides) to blunt end of DNA post hair pin loop cleavage in junctional diversity?

Answer 12

The RAG complex

Question 13

What adds N-nucleotides?

Answer 13

Tdt (terminal deoxynucleotidyl transferase).

These add 1, 2 or 3 nt to either strand

Question 14

What happen if the recombination of gene segments s unsuccessful in making productive protein?

Answer 14

B Cell dies

Question 15

What does somatic hypermutation do?

Answer 15

Increases diversity at CDR regions.

Question 16

What enzyme drives somatic hypermutation?

Answer 16

AID (activation induced cytidine deaminase)

This enzyme is only made proliferating B cells

Question 17

What does AID do?

Answer 17

Converts cytosine to uracil which is then converted to other bases

Question 18

The process of somatic hypermutation drives an event called…?

Answer 18

Affinity maturation

Question 19

What is affinity maturation?

Answer 19

An improvement of binding strength of antibody over time.

Question 20

How does somatic hyper mutation lead to affinity maturation?

Answer 20

• variability generated on variable regions
• antibody on b cells with tightest affinity binds antigen
• this b cell population expands

Question 21

Following rearrangements you get initial transcription which includes which constant gene segments?

Answer 21

mu and delta
(these are the first immunoglobulins to be expressed)
These regions are then processed to give either IgM or IgD

Question 22

Unactivated B cells in the periphery will coexpress which immunoglobulins?

Answer 22

IgM and IgD

They are expressed on the B cells and act as receptors. These have the same VDJ and hence same specificity

Question 23

Between IgM and IgD which exists in the serum?

Answer 23

IgM, following differentiation of B cell into plasma cell IgD is not expressed

Question 24

What generates the difference between membrane bound or secreted IgM?

Answer 24

Alternative Splicing.
There are two exons:
Mc (membrane coding)- M1 and M2
Sc (secretion coding)

Question 25

Is the secreted or the membrane form of IgM pentameric?

Answer 25

secreted

membrane bound is monomeric

Question 26

Which terminus of the heavy chain determines whether the IgM is membrane bound or secreted?

Answer 26

The c terminus. As this is what determines whether the protein is anchored in the membrane or trafficked to ER to form a pentamer prior to secretion.

Question 27

How many amino acids of the C terminus of IgM are identical regardless of whether it is secreted or membrane bound?

Answer 27

556 aa.

After this amino acids are more hydrophillic or hydrophobic depending on whether they are secreted or membrane bound

Question 28

In the membrane bound form of IgM are there negative amino acids on the cytoplasmic end or on the outside?

Answer 28

Negative aa are on the outside and pisotive charges on cytoplasmic.

Question 29

What is class switching?

Answer 29

Changing the class of immunoglobulin that the cell expresses.

Question 30

What is the first immunoglobulin to be produced post production of IgM?

Answer 30

IgG

remember IgD is not expressed in activated B cells

Question 31

What dictates which antibody classes are made following stimulation?

Answer 31

Cytokines dictate which antibody classes are made

Question 32

What catlyses the class switching?

Answer 32

AID