B Cell Diversity-L5 Flashcards Preview

Immunology > B Cell Diversity-L5 > Flashcards

Flashcards in B Cell Diversity-L5 Deck (12):
1

Types of light chains

lambda and kappa (only seen in V and J regions)

2

Gene segment types

-J region
-D region
-V region

3

How are V, D, and J brought together?

Recombinase genes RAG1 and RAG2

4

Signal sequences

Determines which immunoglobulin gene segments can be joined to each other

5

Generation of functional diversity

-RAG cleaves heptamer RSSs from the D and J gene segments to yield DNA hairpins
-RAG opens hairpins and generates palindromic P-nucleotides
-N-nucleotide additions by TdT
-Strands paired
-Unpaired nucleotides removed by exonuclease
-Gaps filled and ligated

6

TdT

-Terminal deoxynucleotidyl transferase
-Only found in developing B cells in the pro B stages after birth
-Add random nucleotides to V-D and D-J joins.

7

Rearrangement in early pro-B cells

-H chain rearrangement
-D-J regions on both chromosomes

8

Rearrangement in late pro-B cells

-H chain rearrangement
-V-DJ rearrangement on both chromosomes

9

Rearrangement in pre-B cells

-L chain rearrangement
-kappa chain on both chromosomes, then gamma
-No N regions (added by TdT) found in light chains

10

IgD formation

-Selective splicing of an RNA transcribed from both IgM and IgD constant regions
-Splicing determines whether membrane bound or secreted Ig

11

Class switching and somatic mutations

-Variable region joined to a new constant region
-Doesn't occur for IgD
-Variable region undergoes a high rate of mutation--yields amino acids that improve antigen binding
-Somatic mutations limited to variable region of Ig
-Enzyme: Activation induced cytidine deaminase (AID)

12

T cell receptor

-NO somatic hypermutation, most other mechanisms the same as the B-cell.