Lecture 5- Adaptive immunity 2- Part 3

Question 1

What is the purpose of antibody class switch recombination (CSR)?

Answer 1

• Allows for SUBSTITUTION for one type of isotype for another
• Provides antibody with NEW FUNCTIONS

Question 2

What is the induction of class switch recombination orchestrated by?

Answer 2

• Different CYTOKINES that result from cellular interactions of the B Cell with different types of T Cell
• These interactions direct Class Switch recombination towards a specific isotype

Question 3

Where does the antibody class switch recombination occur?

Answer 3

• HEAVY CHAIN ANTIBOY LOCUS

- This is the location of different constant region genes that encode each isotype

Question 4

Does the class switch recombination change the affinity of the BCR for antigen?

Answer 4

No-Tunes the B cell response
- Allows long term B memory Cells- Class switched B cells can become long livid plasma cells (antibody secreting cells) or memory B cell.

Question 5

What is the switch region and where is it found?

Answer 5

SPECIFIC SEQUENCE OF DNA that lie UPSTREAM of each set of constant region genes

Question 6

what does each switch region associated with?

Answer 6

• Upstream promoter

- Exon

Question 7

what is the function of upstream promoter and exon?

Answer 7

-Production of STERILE (noncoding) GERMLINE TRANSCRIPTS through the S-region

Question 8

Which antibody lacks S-region and how is it produced?

Answer 8

• IgD- constant region lacks a defined switch region

- IgD is generated through splicing mechanism with the μ constant region

Question 9

what is always the first targeted switch region?

Answer 9

Su switch region which lies downstream of VDJ sequence of the heavy chain

Question 10

What is the other partner switch region determined by?

Answer 10

-Specific CYTOKINES secreted by the T helper cell involved in the B cell activation

Question 11

What does Activation-induced cytidine deaminase enzyme do?

Answer 11

Changes CYTADINE bases for URACIL which are then excised by uracil- N-glycosylase creating DNA strand breaks

Question 12

How are the double-stranded DNA breaks at both switch regions brought together?

Answer 12

-By DNA DAMAGE REPAIR MACHINERY and SPLICED together thereby removing all of the intervening DNA

Question 13

What is the result of splicing together both switch regions?

Answer 13

-Active transcript downstream of the VDJ sequence resulting in:
the transcription of a NEW CONSTANT REGION

Question 14

Why does Class switch recombination matter?

Answer 14

-Determines the type of response that immunoglobulin can promote