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Loss of precursor B cell expansion but not allelic exclusion in VpreB1/VpreB2 double-deficient mice.

Mundt C, Licence S, Shimizu T, Melchers F, Mårtensson IL - J. Exp. Med. (2001)

Bottom Line: Pre-BII cells did not expand by proliferation, consequently 40-fold less small pre-BII and immature B cells were found in bone marrow, and the generation of immature and mature conventional B cells in spleen appeared reduced.In addition, only low numbers of B-1a cells were detected in the peritoneum.Surprisingly, Ig heavy chain allelic exclusion was still active, apparently ruling out a signaling role of a VpreB1/VpreB2-containing receptor in this process.

View Article: PubMed Central - PubMed

Affiliation: Developmental Immunology, The Babraham Institute, Cambridge CB2 4AT, United Kingdom.

ABSTRACT
The pre-B cell receptor consists of immunoglobulin (Ig) mu heavy chains and surrogate light chain, i.e., the VpreB and lambda5 proteins. To analyze the role of the two VpreB proteins, mice lacking the VpreB1 and VpreB2 genes were generated. VpreB1(-/-) VpreB2(-/-) mice were impaired in their B cell development at the transition from pre-BI to large pre-BII cells. Pre-BII cells did not expand by proliferation, consequently 40-fold less small pre-BII and immature B cells were found in bone marrow, and the generation of immature and mature conventional B cells in spleen appeared reduced. In addition, only low numbers of B-1a cells were detected in the peritoneum. Surprisingly, Ig heavy chain allelic exclusion was still active, apparently ruling out a signaling role of a VpreB1/VpreB2-containing receptor in this process.

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Impaired B cell development in VpreB1−/− VpreB2−/− mice. (A) FACS® analysis of bone marrow cells from VpreB1+/−VpreB2+/− (top) and VpreB1−/−VpreB2−/− (bottom) ES94-derived 10-d-old littermates. Cells were stained for B220 (CD45R) in combination with either CD19, c-kit (CD117), CD25, IgM, or IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (B) FACS® analysis of spleen cells from the mice in A. Cells were stained for B220 in combination with CD19, IgM, IgD, or Igλ, and also with IgM in combination with IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (C) FACS® analysis of peritoneal cells from VpreB1+/+VpreB2+/+ and VpreB1−/−VpreB2−/− ES94 mice stained for B220 and CD5 aged 12 d and 12 wk, respectively. Cells falling within the lymphocyte gate are displayed. The numbers indicate the percentage of cells within these regions.
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Figure 3: Impaired B cell development in VpreB1−/− VpreB2−/− mice. (A) FACS® analysis of bone marrow cells from VpreB1+/−VpreB2+/− (top) and VpreB1−/−VpreB2−/− (bottom) ES94-derived 10-d-old littermates. Cells were stained for B220 (CD45R) in combination with either CD19, c-kit (CD117), CD25, IgM, or IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (B) FACS® analysis of spleen cells from the mice in A. Cells were stained for B220 in combination with CD19, IgM, IgD, or Igλ, and also with IgM in combination with IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (C) FACS® analysis of peritoneal cells from VpreB1+/+VpreB2+/+ and VpreB1−/−VpreB2−/− ES94 mice stained for B220 and CD5 aged 12 d and 12 wk, respectively. Cells falling within the lymphocyte gate are displayed. The numbers indicate the percentage of cells within these regions.

Mentions: To determine at which point of development the defect in both VpreB genes impedes B-lineage cell generation the sizes of cellular pools of pre-BI, large and small pre-BII, and immature and mature B cells in bone marrow were determined by FACS® analysis using B220, CD19, c-kit, CD25, and cell size as distinguishable markers (Fig. 3 A and Table ). VpreB1/VpreB2 double-deficient mice showed an about twofold increase in the number of B220+c-kit+ pre-BI cells compared with control mice. The number of CD19+c-kit+ cells was also increased about twofold (data not shown). By contrast, the number of B220+CD25+ pre-BII cells was severely reduced. In young mice, the difference in cell numbers, compared with control littermates, was ∼40-fold, whereas it was ∼10-fold in older mice. These results suggest that the lack of VpreB1 and VpreB2 expression result in a defect in the generation of pre-BII from pre-BI cells, i.e., at the stage of surface pre-BCR expression.


Loss of precursor B cell expansion but not allelic exclusion in VpreB1/VpreB2 double-deficient mice.

Mundt C, Licence S, Shimizu T, Melchers F, Mårtensson IL - J. Exp. Med. (2001)

Impaired B cell development in VpreB1−/− VpreB2−/− mice. (A) FACS® analysis of bone marrow cells from VpreB1+/−VpreB2+/− (top) and VpreB1−/−VpreB2−/− (bottom) ES94-derived 10-d-old littermates. Cells were stained for B220 (CD45R) in combination with either CD19, c-kit (CD117), CD25, IgM, or IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (B) FACS® analysis of spleen cells from the mice in A. Cells were stained for B220 in combination with CD19, IgM, IgD, or Igλ, and also with IgM in combination with IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (C) FACS® analysis of peritoneal cells from VpreB1+/+VpreB2+/+ and VpreB1−/−VpreB2−/− ES94 mice stained for B220 and CD5 aged 12 d and 12 wk, respectively. Cells falling within the lymphocyte gate are displayed. The numbers indicate the percentage of cells within these regions.
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Related In: Results  -  Collection

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Figure 3: Impaired B cell development in VpreB1−/− VpreB2−/− mice. (A) FACS® analysis of bone marrow cells from VpreB1+/−VpreB2+/− (top) and VpreB1−/−VpreB2−/− (bottom) ES94-derived 10-d-old littermates. Cells were stained for B220 (CD45R) in combination with either CD19, c-kit (CD117), CD25, IgM, or IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (B) FACS® analysis of spleen cells from the mice in A. Cells were stained for B220 in combination with CD19, IgM, IgD, or Igλ, and also with IgM in combination with IgD. Cells falling within the lymphocyte gate are displayed. Numbers indicate percentage of cells within this quadrant. (C) FACS® analysis of peritoneal cells from VpreB1+/+VpreB2+/+ and VpreB1−/−VpreB2−/− ES94 mice stained for B220 and CD5 aged 12 d and 12 wk, respectively. Cells falling within the lymphocyte gate are displayed. The numbers indicate the percentage of cells within these regions.
Mentions: To determine at which point of development the defect in both VpreB genes impedes B-lineage cell generation the sizes of cellular pools of pre-BI, large and small pre-BII, and immature and mature B cells in bone marrow were determined by FACS® analysis using B220, CD19, c-kit, CD25, and cell size as distinguishable markers (Fig. 3 A and Table ). VpreB1/VpreB2 double-deficient mice showed an about twofold increase in the number of B220+c-kit+ pre-BI cells compared with control mice. The number of CD19+c-kit+ cells was also increased about twofold (data not shown). By contrast, the number of B220+CD25+ pre-BII cells was severely reduced. In young mice, the difference in cell numbers, compared with control littermates, was ∼40-fold, whereas it was ∼10-fold in older mice. These results suggest that the lack of VpreB1 and VpreB2 expression result in a defect in the generation of pre-BII from pre-BI cells, i.e., at the stage of surface pre-BCR expression.

Bottom Line: Pre-BII cells did not expand by proliferation, consequently 40-fold less small pre-BII and immature B cells were found in bone marrow, and the generation of immature and mature conventional B cells in spleen appeared reduced.In addition, only low numbers of B-1a cells were detected in the peritoneum.Surprisingly, Ig heavy chain allelic exclusion was still active, apparently ruling out a signaling role of a VpreB1/VpreB2-containing receptor in this process.

View Article: PubMed Central - PubMed

Affiliation: Developmental Immunology, The Babraham Institute, Cambridge CB2 4AT, United Kingdom.

ABSTRACT
The pre-B cell receptor consists of immunoglobulin (Ig) mu heavy chains and surrogate light chain, i.e., the VpreB and lambda5 proteins. To analyze the role of the two VpreB proteins, mice lacking the VpreB1 and VpreB2 genes were generated. VpreB1(-/-) VpreB2(-/-) mice were impaired in their B cell development at the transition from pre-BI to large pre-BII cells. Pre-BII cells did not expand by proliferation, consequently 40-fold less small pre-BII and immature B cells were found in bone marrow, and the generation of immature and mature conventional B cells in spleen appeared reduced. In addition, only low numbers of B-1a cells were detected in the peritoneum. Surprisingly, Ig heavy chain allelic exclusion was still active, apparently ruling out a signaling role of a VpreB1/VpreB2-containing receptor in this process.

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