Receptor Editing in a Transgenic Mouse Model: Site, Efficiency, and Role in B Cell Tolerance and Antibody Diversification

Positive selection is required for B cell differentiation, as indicated by the requirement for expression of the pre-B cell receptor (pre-BCR) and the BCR at the pre-B and immature B cell stages, respectively. Positive selection mediated by a tonic signal from these receptors is sufficient to drive B cell differentiation beyond the pre-B and immature B cell stages, but it is unclear whether additional positive selection signals are required for differentiation to a mature B-2 cell. We have identified a population of Ig transgenic B cells that differentiatively arrest at a transitional B cell stage in the spleen. They exhibit no evidence of Ag encounter or negative selection and can differentiate to mature B-2 cells in vivo upon weak BCR stimulation or adoptive transfer to irradiated hosts. These data are consistent with a requirement for a ligand-mediated BCR signal for differentiation to a mature B-2 cell.

Section: Discussionmentioning

confidence: 99%

Evidence for a Ligand-Mediated Positive Selection Signal in Differentiation to a Mature B Cell

Wang

Clarke

2003

“…It has been shown that while an autoreactive BCR will induce L chain gene rearrangement, a nonautoreactive BCR will not (31). Although editing in ⌬V mice cannot be manifested by a change in L chain, because ⌬V receptors do not contain L chains, it is possible to evaluate the nature and the extent of L chain gene rearrangement by semiquantitative methods (24).…”

Section: Evidence For Secondary L Chain Gene Rearrangement In ⌬V Cellsmentioning

confidence: 99%

Expression of a V Region-Less B Cell Receptor Confers a Tolerance-Like Phenotype on Transgenic B Cells

Corcos

Grandien

Vázquez

et al. 2001

Neoplastic B cells from H chain disease patients express a truncated B cell receptor (BCR), comprising a membrane Ig that lacks part of its extracellular domain. It has been speculated that deletion of the Ag binding domain would confer a constitutive activity on the BCR, as it has been shown for oncogenic growth factor receptors. A V region-less BCR has constitutive activity, because in transgenic mice it causes inhibition of endogenous H chain gene rearrangements and relieves the requirement for surrogate L chain in pre-B cell development. However, it has been speculated that normal Ag receptors also display constitutive activity. Here we show that transgenic B cells expressing a membrane H chain disease protein on their surface are phenotypically and functionally similar to B cells developing in the presence of their cognate Ag and that cells with normal levels of mutant BCR are eliminated in spleen via a bcl-2 sensitive pathway while progressing toward the mature stage. In contrast, cells with lower levels of mutant receptors develop as mature B cells. These findings support the view that the truncated BCR has a constitutive activity that mimics ligand binding, in analogy to what has been shown for oncogenic growth factor receptors.

“…However, the expression of a functional BCR does not always terminate light chain gene rearrangement (6). One well-documented situation in which rearrangement continues is when the Ag receptors on the newly formed immature B cells possess autoreactive specificity (7)(8)(9). This secondary V(D)J rearrangement, referred to as receptor editing, occurs in IgM ϩ , IgD Ϫ immature B cells in the bone marrow (10,11).…”

mentioning

confidence: 99%

Secondary V(D)J Rearrangements and B Cell Receptor-Mediated Down-Regulation of Recombination Activating Gene-2 Expression in a Murine B Cell Line

Maës

Caspi

Rougeon

et al. 2000

It has recently become clear that recombination of Ig genes is not restricted to B cell precursors but that secondary rearrangements can also occur under certain conditions in phenotypically immature bone marrow and peripheral B cells. However, the nature of these cells and the regulation of secondary V(D)J recombination in response to B cell receptor (BCR) stimulation remain controversial. In the present study, we have analyzed secondary light chain gene rearrangements and recombination activating gene (RAG) expression in the surface IgM+, IgD− murine B cell line, 38C-13, which has previously been found to undergo κ light chain replacement. We find that 38C-13 cells undergo spontaneous secondary Vκ-Jκ and RS rearrangements in culture, with recombination occurring on both productive and nonproductive alleles. Both 38C-13 cells and the Id-negative variants express the RAG genes, indicating that the presence of RAG does not depend on activation via the 38C-13 BCR. Moreover, BCR cross-linking in 38C-13 cells leads to a rapid and reversible down-regulation of RAG2 mRNA. Therefore, 38C-13 cells resemble peripheral IgM+, IgD− B cells undergoing light chain gene rearrangement and provide a possible in vitro model for studying peripheral V(D)J recombination.