Biased immunoglobulin variable region gene expression by Ly‐1 B cells due to clonal selection

Recombinant annexin V (rAnV) has been used in flow cytometry to identify cells undergoing apoptosis, based on its ability to bind to phosphatidylserine, a negatively charged lipid normally restricted to the cytoplasmic face of the plasma membrane but externalized early during apoptosis. When we stained murine bone marrow (BM) cells with fluorescently labeled rAnV, we found that a surprisingly large fraction of BM B cells bearing selectable transgenic Ag receptors bind significant amounts of rAnV, but that these cells are not apoptotic. Here, we show that binding of rAnV to developing B cells in normal mice correlates with B cell receptor-dependent selection events at several stages of development within both B-1 and B-2 cell subsets. In fact, nearly all B-1 B cells and splenic marginal zone B cells bind rAnV, suggesting that the externalization of phosphatidylserine occurs once mature B cells are selected through BCR-mediated signaling. However, this plasma membrane alteration is apparently not shared by all lymphocytes, because we did not find a parallel population of rAnV-binding viable T cells in vivo in normal or TCR transgenic mice. We also show that BM stromal cell lines can influence the extent of rAnV binding by viable BM B cells during coculture in vitro. We suggest that rAnV detects a potentially important membrane alteration that occurs as B cells develop in the BM and are readied for export to the peripheral lymphoid organs and again among mature B cells recruited to the marginal zone or the B-1 compartment.

Section: Recombinant Anv Marks Selected Pro-b and Immature B Cellsmentioning

confidence: 73%

mentioning

confidence: 99%

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confidence: 99%

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Annexin V Binds to Positively Selected B Cells

Dillon

Constantinescu

Schlissel

2001

“…However, most of these cells were found within the CD5 ϩ population in the adult. Previously, in adult mice, B cells with canonical receptors containing particular V H -D-J H /V -J junctions were reported in association with the B1 phenotype (22,45,46). In addition, selection of certain V H -J -bearing clones into the mature long-lived B cell pool (46), and BCR-directed selection of V H 81x-V 1C and V H S107-V 24 clones into the splenic marginal zone were recently reported (47).…”

Section: Discussionmentioning

confidence: 97%

The VλJλ Repertoire in Human Fetal Spleen: Evidence for Positive Selection and Extensive Receptor Editing

Lee

Monson

Lipsky

2000

VλJλ rearrangements obtained from genomic DNA of individual IgM+ B cells from human fetal spleen were analyzed. A nonrandom pattern of λ gene rearrangements that differed from the adult Vλ repertoire was found. The Vλ distal genes 8A and 4B were absent from the nonproductive fetal repertoire, whereas 2E and 3L were overrepresented and 1B was underrepresented in the productive fetal repertoire. Positive selection of the Vλ gene, 2E, along with Vλ rearrangements employing homologous VλJλ joins were observed in the fetal, but not in the adult Vλ repertoire. Overrepresentation of Jλ distal cluster C genes rearranging to the Vλ distal J segment, Jλ7, in both productive and nonproductive fetal repertoires suggested that receptor editing/replacement was more active in the fetus than in adults. Numerous identical VλJλ junctions were observed in both the productive and nonproductive repertoire of the fetus and adult, but were significantly more frequent in the productive repertoire of the fetus, suggesting expansion of B cells expressing particular λ-light chains in both stages of development, with more profound expansion in the fetal repertoire. Notably, B cells expressing identical λ-light chains expressed diverse heavy chains. These data demonstrate that three mechanisms strongly influence the shaping of the human fetal λ-chain repertoire that are less evident in the adult: positive selection, receptor editing, and expansion of B cells expressing specific λ-light chains. These events imply that the expressed fetal repertoire is shaped by exposure to self Ags.

“…In these studies, B-1 cell development appeared to correlate with Ag receptor specificity. Recognition of self Ag, either endogenously or transgenically expressed, was shown to be necessary for the generation and expansion of the B-1 cell population (18,21,23). The pleural and peripheral compartments of these mice become replete with cells bearing the B-1 phenotype.…”

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confidence: 99%

The Unique Antigen Receptor Signaling Phenotype of B-1 Cells Is Influenced by Locale but Induced by Antigen

Chumley

Porto

Cambier

2002

Normal animals contain an autoreactive B lymphocyte subset, the B-1 subset, which is controlled by undefined mechanisms to prevent autoimmunity. Using a VH11Vκ9 Ig transgenic mouse, with a specificity prototypic of the subset, we have explored conditions responsible for the previously reported Ag hyporesponsiveness of these cells. We report that peritoneal VH11Vκ9 B cells exhibit typical B-1 behavior with high basal intracellular free Ca2+ and negligible receptor-mediated calcium mobilization. However, splenic B cells from this mouse, while phenotypically similar to their peritoneal counterparts, including expression of CD5, mount robust B-2-like responses to Ag as measured by calcium influx and altered tyrosine phosphorylation responses. When these splenic cells are adoptively transferred to the peritoneal cavity and encounter their cognate self-Ag, they acquire a B-1 signaling phenotype. The ensuing hyporesponsiveness is characterized by increases in both basal intracellular calcium and resting tyrosyl phosphorylation levels and is highlighted by a marked abrogation of B cell receptor-mediated calcium mobilization. Thus, we show that self-Ag recognition in specific microenvironments such as the peritoneum, and we would propose other privileged sites, confers a unique form of anergy on activated B cells. This may explain how autoreactive B-1 cells can exist while autoimmunity is avoided.