Concanavalin A stimulation enhanced secondary V(λ)J(λ) rearrangement in some human plasma B cells without up-regulation of recombination- activating gene expression and V(λ) germline transcription

Light chain shifting is a phenomenon that occurs in certain human antibody-producing plasma B cells which, when stimulated with concanavalin A (Con A), shift production of the original light chain to new light chains. Here we investigated the effect of Con A stimulation on these light chain shift-inducible cells. Analysis of transcripts and VJ-coding joints for new light chains revealed that a leaky amount of secondary V(λ)J(λ) rearrangement occurs spontaneously, without Con A stimulation, and that Con A stimulation markedly increases VJ-coding joints and transcripts for new light chains. It was also shown that new light chain producers, which have carried out secondary rearrangement, do not further rearrange their light chain genes, even when stimulated with Con A. Recombination-activating gene (RAG) products and V(λ) germline transcription were constitutively expressed in these cell lines and their expression levels were not affected by Con A stimulation. These results suggest that Con A stimulation enhanced secondary V(λ)J(λ) rearrangement, but this was not a result of the up-regulation of RAG expression and V(λ) germline transcription, which are believed to be sufficient for the process of V(λ)J(λ) rearrangement.