Conserved distribution of λ subtypes from rearranged gene segments to immunoglobulin synthesis in the mouse B cell repertoire

Abstract

The immunoglobulin lambda light chain system displays a limited diversity in inbred mice. Indeed, the lambda locus is organized in two recombination units: V lambda 2-V lambda x-J lambda 2-C lambda 2-psi J lambda 4-psi C lambda 4, which can produce either lambda 2(V2) or lambda 2(Vx) chains; and V lambda 1-J lambda 3-C lambda 3-J lambda 1-C lambda 1, which can produce either lambda 1 or lambda 3 chains. Each of these units is associated with an enhancer, E lambda 2-4 or E lambda 1-3, at the 3' side. The expression of each lambda chain is, therefore, controlled by distinct promoter and/or enhancer regions. To clarify the basis of these controls, we measured, by quantitative polymerase chain reaction, the proportions of each lambda subtype in BALB/c spleen mRNA and among genomic rearrangements. It appears that these distributions are similar to and consistent with the relative cellular frequencies in the spleen, as evaluated by flow cytometry. These results suggest that, in resting cells, the transcription rates are identical, regardless of the lambda subtype. After lipopolysaccharide (LPS) stimulation, the transcription rates per cell remain similar for all lambda subtypes despite different regulatory sequences. To detect eventual post-transcriptional regulations, we estimated the lambda light chain distribution in IgM secreted by LPS-stimulated B cells and in serum IgG. These distributions are still similar to those of lambda-expressing cells, lambda mRNA or genomic rearrangements. We conclude that the lambda subtype distribution is conserved from productive V-J rearranged genes to secreted lambda immunoglobulins, despite different regulatory sequences.

Various V‐J rearrangement efficiencies shape the mouse λ B cell repertoire

“…These data are in agreement with other reports and our previous observations in normal mice (reviewed in [5,6,81). …”

“…As we observed 12 V2J2 productive joints for 5 V1J3 (see Fig. 1) we can estimate that there are 18 YO of h2(V2) cells and 8 Yo of h3 cells since these joints are co-amplified with the same efficiency [6]. Furthermore, we show that the profiles of productive junctions are globally conserved among the bone marrow pre-B cells and the mature spleen.…”

“…These mouse strains, therefore, represent a good model to increase our knowledge of the rules that govern the establishment of the B cell repertoire, by studying the proportions of different VhThCh combinations. Results obtained on the normal or mutant mice have shown a clear dominance of the hl subtype (except in the SJL strain [7]) and an underrepresentation of the h3 subtype among spleen cells (reviewed in [5,6,81). However, the determination of the unequal h subtype repartition is largely debated.…”

Cut-and-Run: A Distinct Mechanism by which V(D)J Recombination Causes Genome Instability

“…Because these “open” ESCs could potentially undergo re-integration, rather than cut-and-run, we were keen to assess the level of unligated signal ends in vivo . To this end, we examined the Igλ locus where 60%–70% of recombination occurs between Vλ1 and JCλ1 (Boudinot et al., 1994), and thus the Vλ1Jλ1 ESC is generated in the majority of Igλ-positive cells. Using LM-PCR, we find that unligated Vλ1Jλ1 signal ends are detectable, but only weakly (Figure 5C).…”

Does positive selection determine the B cell repertoire?

“…In H3-and M54-Tg mice, we can consider that the potential diversity of B cell receptor is limited to four combinations, i.e. p-transgeneencoded chain with one type of h subtype (the h junctional diversity is extremely restricted [32]). In the hypothesis of a negative selection, three out of four combinations should display autoreactivity against unknown self-antigens in both p-transgenic mice.…”