4: Generation of Antibody Diversity

what are the gene segments that are assembled to create the variable region of an immunoglobulin heavy chain?

V, D, and J segments

what are the gene segments that are assembled to create the variable region of an immunoglobulin light chain?

V and J segments

what is the enzyme responsible for adding random nucleotides at the V-D and D-J junctions in heavy chains?

TdT

what is the process that brings V, D, and J segments together?

recombination

what is the first gene rearrangement that occurs in an early pro-B cell?

H-chain gene rearrangement

what is the rearrangement that happens after a successful H-chain rearrangement?

L-chain gene rearrangement

what happens to a B-cell precursor if a rearrangement is nonproductive?

apoptosis

which is the immunoglobulin expressed by a B cell after a productive heavy chain and kappa light chain rearrangement?

IgM

what is the process that rearranges V, D, and J gene segments before a B cell encounters an antigen?

somatic recombination

what is a mechanism that increases diversity after a B cell encounters an antigen and gets T cell help?

somatic hypermutation

what is the enzyme involved in both class switching and somatic mutation?

activation-induced cytidine deaminase (AID)

what is the type of splicing that allows a B cell to switch from IgM to IgD?

RNA splicing

what is the type of splicing that permanently changes the DNA during class switching (except to IgD)?

DNA splicing

what is the order of immunoglobulin gene arrangement?

• D-J rearrangement on both heavy-chain chromosomes

• V-DJ arrangement on the first chromosome, then on second if first is nonproductive

• kappa light-chain rearrangement on the first chromosome, then on second

• lambda light-chain rearrangement if needed

what would happen to B cells in an individual who does not have any RAG?

gene segments could not be joined and immunoglobulin genes could not be formed

can the IgM to IgG class switching be reversed?

no because it is a permanent DNA splice

what would be the consequence if the AID enzyme was absent in an individual?

the B cell would be unable to perform class switching or somatic hypermutation