3.1 Genetics of Antibody Diversity and Ig Gene Recombination

Vocabulary flashcards covering innate/adaptive receptor differences, Ig gene organization, somatic recombination, diversity generation, and isotype switching.

Innate immune receptors (PRRs)

Pattern recognition receptors that recognize shared pathogen structures; are always available with a fixed repertoire.

Adaptive immune receptors (BCRs and TCRs)

Receptors generated by B and T cells; immense diversity; each lymphocyte expresses a single type of receptor.

Germline configuration

Ig gene segments exist as separate pieces in germline DNA and are not expressed until rearranged.

Somatic recombination

Rearrangement of Ig gene segments (V, D, J) in developing B cells to assemble a functional gene.

V(D)J recombinase

Enzyme complex mediating recombination, including RAG-1 and RAG-2 and DNA repair components.

RAG-1 and RAG-2

Lymphocyte-specific enzymes essential for initiating V(D)J recombination.

Recombination Signal Sequences (RSS)

Noncoding sequences that flank V, D, J segments and guide segment joining.

Heavy-chain variable region (V_H)

Variable part of the heavy chain formed by joining V, D, and J segments.

Light-chain variable region (V_L)

Variable part of the light chain formed by joining V and J segments.

Combinatorial diversity

Diversity from selecting different V, D, J segments and pairing heavy and light chains.

Junctional diversity

Extra diversity from imprecise joining at V(D)J junctions, including added nucleotides.

P nucleotides

Palindromic nucleotides added at hairpin openings during recombination.

N nucleotides

Non-templated nucleotides added by TdT at junctions, increasing diversity.

TdT (terminal deoxynucleotidyl transferase)

Enzyme that randomly adds N nucleotides during V(D)J recombination.

Coding joint vs signal joint

Coding joint forms the functional Ig gene; signal joint is discarded after recombination.

Somatic hypermutation

Post-activation mutations in V regions that increase antibody affinity.

Affinity maturation

Selection of B cells with higher-affinity BCRs during the immune response.

Isotype switching (class-switch recombination)

Changing the heavy-chain constant region (e.g., IgM to IgG) while keeping the variable region.