Reexpression of the V(D)J recombinase-activating genes RAG1 and RAG2 i
n germinal center B cells creates the potential for immunoglobulin gen
e rearrangement and the generation of new antigen receptor specificiti
es. intermediate products of V(D)J recombination are abundant in a sub
set of germinal center B cells, demonstrating that the kappa immunoglo
bulin light-chain locus becomes a substrate for renewed V(D)J recombin
ase activity. This recombinationally active cell compartment contains
many heavy-chain VDJ rearrangements that encode low-affinity or nonfun
ctional antibody. In germinal centers, secondary V(D)J recombination m
ay be induced by diminished binding to antigen ligands, thereby limiti
ng abrupt changes in receptor specificity to B cells that are usually
eliminated from the germinal center reaction, This restriction preserv
es efficient antigen-driven selection in germinal centers while allowi
ng for saltations in the somatic evolution of B cells.