Limits...
Inhibition of interleukin 7 receptor signaling by antigen receptor assembly.

Smart FM, Venkitaraman AR - J. Exp. Med. (2000)

Bottom Line: This is confirmed by introduction of a rearranged lambda light chain gene, which inhibits proliferative signaling through the IL-7R.Our findings identify a novel mechanism that limits cytokine-dependent proliferation during B lymphopoiesis.This mechanism may be essential for the proper regulation of peripheral B lymphocyte numbers.

View Article: PubMed Central - PubMed

Affiliation: Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, and the Cancer Research Campaign Department of Oncology, University of Cambridge, The Cambridge Institute for Medical Research, Cambridge CB2 2XY, United Kingdom.

ABSTRACT
After the productive rearrangement of immunoglobulin (Ig) heavy chain genes, precursor (pre-)B lymphocytes undergo a limited number of cell divisions in response to interleukin (IL)-7. Here, we present evidence that this phase of IL-7-dependent expansion is constrained by an inhibitory signal initiated by antigen receptor assembly. A line of pre-B cells from normal murine bone marrow that expresses a mu heavy chain with a D-proximal V(H)7183.2 region divides continuously in IL-7. IL-7 responsiveness ceases upon differentiation to the mu(1), kappa(1) stage, despite continuing expression of the IL-7 receptor (IL-7R), suggesting that antigen receptor assembly inhibits IL-7 responsiveness. This is confirmed by introduction of a rearranged lambda light chain gene, which inhibits proliferative signaling through the IL-7R. Inhibition is specific to the IL-7R, because it is overcome by replacement of the IL-7R cytoplasmic domain with corresponding sequences from the closely related IL-2Rbeta chain. Alteration of a single tyrosine residue, Tyr410, in the IL-7R cytoplasmic domain to phenylalanine also prevents the inhibition of proliferation after antigen receptor assembly. Thus, the loss of IL-7 responsiveness after antigen receptor assembly may be mediated through the recruitment of an inhibitory molecule to this residue. Our findings identify a novel mechanism that limits cytokine-dependent proliferation during B lymphopoiesis. This mechanism may be essential for the proper regulation of peripheral B lymphocyte numbers.

Show MeSH
(A) Shows that markers characteristic of the pre-B I stage in differentiation are expressed by the pre-B cell line used in these studies. The panels show the results of flow cytometric analyses of 10,000 cells after staining with antibodies against the indicated markers. Forward and side light scatter profiles were used to exclude dead cells. (B) Demonstrates the dose-dependent proliferation of the pre-B cells in response to IL-7. Proliferation quantified by the MTT assay is plotted on the y-axis against cytokine dose on the x-axis. The solid and dotted lines compare the proliferation of a pre-B cell culture tested at an interval of >1 yr, showing that IL-7–dependent proliferation is not lost after prolonged passage in culture. Results are typical of at least three independent experiments.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2195828&req=5

Figure 1: (A) Shows that markers characteristic of the pre-B I stage in differentiation are expressed by the pre-B cell line used in these studies. The panels show the results of flow cytometric analyses of 10,000 cells after staining with antibodies against the indicated markers. Forward and side light scatter profiles were used to exclude dead cells. (B) Demonstrates the dose-dependent proliferation of the pre-B cells in response to IL-7. Proliferation quantified by the MTT assay is plotted on the y-axis against cytokine dose on the x-axis. The solid and dotted lines compare the proliferation of a pre-B cell culture tested at an interval of >1 yr, showing that IL-7–dependent proliferation is not lost after prolonged passage in culture. Results are typical of at least three independent experiments.

Mentions: We used a line of pre-B cells isolated from normal murine bone marrow 16 to study the mechanisms that limit IL-7 responsiveness during B lymphopoiesis. These cells express markers characteristic of the pre-B I stage in development (Fig. 1 A). Thus, in addition to the CD19 marker typical of the B lineage 22, the cells display the marker CD43, whose expression is lost upon differentiation to the pre-B II stage 10. They also express BP-1 16, whose expression commences at Hardy stage C 10. Finally, the cells fail to display CD25, a marker that commences its expression at the pre-B II stage of B cell development 2324.


Inhibition of interleukin 7 receptor signaling by antigen receptor assembly.

Smart FM, Venkitaraman AR - J. Exp. Med. (2000)

(A) Shows that markers characteristic of the pre-B I stage in differentiation are expressed by the pre-B cell line used in these studies. The panels show the results of flow cytometric analyses of 10,000 cells after staining with antibodies against the indicated markers. Forward and side light scatter profiles were used to exclude dead cells. (B) Demonstrates the dose-dependent proliferation of the pre-B cells in response to IL-7. Proliferation quantified by the MTT assay is plotted on the y-axis against cytokine dose on the x-axis. The solid and dotted lines compare the proliferation of a pre-B cell culture tested at an interval of >1 yr, showing that IL-7–dependent proliferation is not lost after prolonged passage in culture. Results are typical of at least three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2195828&req=5

Figure 1: (A) Shows that markers characteristic of the pre-B I stage in differentiation are expressed by the pre-B cell line used in these studies. The panels show the results of flow cytometric analyses of 10,000 cells after staining with antibodies against the indicated markers. Forward and side light scatter profiles were used to exclude dead cells. (B) Demonstrates the dose-dependent proliferation of the pre-B cells in response to IL-7. Proliferation quantified by the MTT assay is plotted on the y-axis against cytokine dose on the x-axis. The solid and dotted lines compare the proliferation of a pre-B cell culture tested at an interval of >1 yr, showing that IL-7–dependent proliferation is not lost after prolonged passage in culture. Results are typical of at least three independent experiments.
Mentions: We used a line of pre-B cells isolated from normal murine bone marrow 16 to study the mechanisms that limit IL-7 responsiveness during B lymphopoiesis. These cells express markers characteristic of the pre-B I stage in development (Fig. 1 A). Thus, in addition to the CD19 marker typical of the B lineage 22, the cells display the marker CD43, whose expression is lost upon differentiation to the pre-B II stage 10. They also express BP-1 16, whose expression commences at Hardy stage C 10. Finally, the cells fail to display CD25, a marker that commences its expression at the pre-B II stage of B cell development 2324.

Bottom Line: This is confirmed by introduction of a rearranged lambda light chain gene, which inhibits proliferative signaling through the IL-7R.Our findings identify a novel mechanism that limits cytokine-dependent proliferation during B lymphopoiesis.This mechanism may be essential for the proper regulation of peripheral B lymphocyte numbers.

View Article: PubMed Central - PubMed

Affiliation: Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, and the Cancer Research Campaign Department of Oncology, University of Cambridge, The Cambridge Institute for Medical Research, Cambridge CB2 2XY, United Kingdom.

ABSTRACT
After the productive rearrangement of immunoglobulin (Ig) heavy chain genes, precursor (pre-)B lymphocytes undergo a limited number of cell divisions in response to interleukin (IL)-7. Here, we present evidence that this phase of IL-7-dependent expansion is constrained by an inhibitory signal initiated by antigen receptor assembly. A line of pre-B cells from normal murine bone marrow that expresses a mu heavy chain with a D-proximal V(H)7183.2 region divides continuously in IL-7. IL-7 responsiveness ceases upon differentiation to the mu(1), kappa(1) stage, despite continuing expression of the IL-7 receptor (IL-7R), suggesting that antigen receptor assembly inhibits IL-7 responsiveness. This is confirmed by introduction of a rearranged lambda light chain gene, which inhibits proliferative signaling through the IL-7R. Inhibition is specific to the IL-7R, because it is overcome by replacement of the IL-7R cytoplasmic domain with corresponding sequences from the closely related IL-2Rbeta chain. Alteration of a single tyrosine residue, Tyr410, in the IL-7R cytoplasmic domain to phenylalanine also prevents the inhibition of proliferation after antigen receptor assembly. Thus, the loss of IL-7 responsiveness after antigen receptor assembly may be mediated through the recruitment of an inhibitory molecule to this residue. Our findings identify a novel mechanism that limits cytokine-dependent proliferation during B lymphopoiesis. This mechanism may be essential for the proper regulation of peripheral B lymphocyte numbers.

Show MeSH