B Cell Development and VDJ Recombination

These flashcards provide key concepts and definitions regarding B cell development and VDJ recombination as covered in the lecture.

What are the phases of B cell development?

There are six phases: 1) Repertoire assembly; 2) Negative selection; 3) Positive selection; 4) Searching for infection; 5) Finding infection; 6) Attacking infection.

Which proteins are essential for B cell development?

FLT3 (signaling), Kit (growth), IL-7 receptor (early factor), RAG-1 and -2 (recombinase), and others involved in signaling and differentiation.

What occurs during negative selection of B cells?

B cells with receptors that bind to self-components are altered, eliminated, or inactivated.

What is the role of IL-7 in B cell development?

IL-7 supports the growth and survival of B cells during their development.

What are the components of the antigen binding site in antibodies?

The antigen binding site is made up of amino acids from the variable regions of both the heavy and light chains.

How does receptor diversity occur in B and T cells?

Receptor diversity is achieved through random irreversible rearrangement of multiple germline gene segments.

What is the '12/23 rule' in immunoglobulin gene rearrangement?

The '12/23 rule' states that recombination signal sequences (RSS) must be positioned 12 base pairs apart from one another to enable proper joining of gene segments.

What happens if VDJ recombination fails in B cell development?

If VDJ recombination fails to create a functional heavy chain, the cell will attempt rearrangement at the other heavy chain locus, and if still unsuccessful, the cell undergoes apoptosis.

What two types of nucleotide additions contribute to junctional diversity in antibodies?

Palindromic (P) additions and non-template encoded (N) additions.

What results from successful heavy chain rearrangement in B cells?

If the heavy chain rearrangement is successful, the pre-B cell receptor forms with VpreB/lambda5, allowing for further development.

What is the significance of RAG proteins in B cell development?

RAG proteins are necessary for cleaving genomic DNA sequences during V(D)J recombination, enabling the formation of B cell receptors.

What occurs during class switching of immunoglobulins?

The antigen-binding sites of BCRs/antibodies are modified to improve binding affinities, allowing for different isotypes.

What mechanisms eliminate self-reactive B cells during development?

Self-reactive B cells are eliminated through a process called negative selection to prevent autoimmunity.

What is the outcome of successful BCR rearrangement in terms of cell surface expression?

Successfully rearranged B cells will express surface immunoglobulin (IgM) or other variants depending on the isotype switching.