Baff Mediates Survival of Peripheral Immature B Lymphocytes (original) (raw)
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The Journal of Immunology, 2004
The cytokine TNF family member B cell-activating factor (BAFF; also termed BLyS) is essential for B cell generation and maintenance. Three receptors have been identified that bind to BAFF: transmembrane activator, calcium modulator, and cyclophilin ligand interactor (TACI); B cell maturation Ag (BCMA); and BAFF-R. Recently, it was shown that A/WySnJ mice, which contain a dramatically reduced peripheral B cell compartment due to decreased B cell life span, express a mutant BAFF-R. This finding, together with normal or enhanced B cell generation in mice deficient for BCMA or TACI, respectively, suggested that the interaction of BAFF with BAFF-R triggers signals essential for the generation and maintenance of mature B cells. However, B cells in mice deficient for BAFF differ phenotypically and functionally from A/WySnJ B cells. Residual signaling through the mutant BAFF-R could account for these differences. Alternatively, dominant-negative interference by the mutant receptor could lead to an overestimation of the importance of BAFF-R. To resolve this issue, we generated BAFF-R-null mice. Baff-r ؊/؊ mice display strongly reduced late transitional and follicular B cell numbers and are essentially devoid of marginal zone B cells. Overexpression of Bcl-2 rescues mature B cell development in Baff-r ؊/؊ mice, suggesting that BAFF-R mediates a survival signal. CD21 and CD23 surface expression are reduced on mature Baff-r ؊/؊ B cells, but not to the same extent as on mature B cells in BAFF-deficient mice. In addition, we found that Baff-r ؊/؊ mice mount significant, but reduced, Ag-specific Ab responses and are able to form spontaneous germinal centers in mesenteric lymph nodes. The reduction in Ab titers correlates with the reduced B cell numbers in the mutant mice.
European Journal of Immunology, 2004
The TNF family ligand B cell-activating factor (BAFF, BLyS, TALL-1) is an essential factor for B cell development. BAFF binds to three receptors, BAFF-R, transmembrane activator and CAML interactor (TACI), and B cell maturation antigen (BCMA), but only BAFF-R is required for successful survival and maturation of splenic B cells. To test whether the effect of BAFF is due to the up-regulation of anti-apoptotic factors, TACI-Ig-transgenic mice, in which BAFF function is inhibited, were crossed with transgenic mice expressing FLICE-inhibitory protein (FLIP) or Bcl-2 in the B cell compartment. FLIP expression did not rescue B cells, while enforced Bcl-2 expression restored peripheral B cells and the ability to mount T-dependent antibody responses. However, many B cells retained immaturity markers and failed to express normal amounts of CD21. Marginal zone B cells were not restored and the Tindependent IgG3, but not IgM, response was impaired in the TACI-Ig×Bcl-2 mice. These results suggest that BAFF is required not only to inhibit apoptosis of maturating B cells, but also to promote differentiation events, in particular those leading to the generation of marginal zone B cells.
BAFF Receptor Regulation of Peripheral B-Lymphocyte Survival and Development
BLyS Ligands and Receptors, 2009
B-lymphocyte homeostasis depends on exogenous signals for survival during development and in immune responses to invading pathogens. These signals are continually provided by either tonic or antigen-mediated BCR signals and other trophic factors. B-cell-activating factor (BAFF) has emerged as a key growth factor for B lymphocytes. Through its interaction with a TNF-R family member, BAFF-R or BR3, BAFF promotes survival of both immature and mature B cells. BAFF/BR3 interaction also facilitates BCR-induced B-cell proliferation. Thus, dysregulation of the signals emanating from these receptors leads to autoimmune disease, whereas interference with these signals leads to B-cell immunodeficiencies. Multiple signal transduction pathways, including those involving transcription factor NF-κB, appear to play critical roles in BAFF-mediated B-cell biological responses. Recent studies have revealed that BR3 and BCR are functionally linked and that Bruton's cytoplasmic tyrosine kinase (Btk)/NF-κB signaling plays an essential role in this process. Therefore, the primary objective of this article is to discuss BR3-signaling pathways, and the cooperation with BCR signals, that regulate B-cell survival during development and activation.
Journal of Experimental Medicine, 2000
The tumor necrosis factor (TNF) family member B cell activating factor (BAFF) binds B cells and enhances B cell receptor-triggered proliferation. We find that B cell maturation antigen (BCMA), a predicted member of the TNF receptor family expressed primarily in mature B cells, is a receptor for BAFF. Although BCMA was previously localized to the Golgi apparatus, BCMA was found to be expressed on the surface of transfected cells and tonsillar B cells. A soluble form of BCMA, which inhibited the binding of BAFF to a B cell line, induced a dramatic decrease in the number of peripheral B cells when administered in vivo. Moreover, culturing splenic cells in the presence of BAFF increased survival of a percentage of the B cells. These results are consistent with a role for BAFF in maintaining homeostasis of the B cell population.
BAFF is a survival and maturation factor for mouse B cells
European Journal of Immunology, 2002
Human B cell-activating factor (BAFF) induces mouse surface IgM + B cells of the immature type from bone marrow and of the immature types 1 and 2 from spleen, as well as of the mature type from spleen to increased longevity in tissue culture. BAFF does so polyclonally and without inducing proliferation in any of these B cell subpopulations. BAFF induces phenotypic and functional maturation of immature to mature B cells so that all immature cells loose C1qRp (AA4.1, 493) expression and type 1 immature cells up-regulate IgD, CD21 and CD23. Immature B cells of types 1 and 2, upon pre-incubation with BAFF, change their reactiveness to Ig-specific antibodies so that they no longer enter apoptosis but now proliferate. However, BAFF does not seem to overcome negative selection of developing immature B cells in vitro.
Cutting Edge: BAFF Regulates CD21/35 and CD23 Expression Independent of Its B Cell Survival Function
The Journal of Immunology, 2004
Herein we demonstrate that B cell-activating factor of the TNF family (BAFF), a B cell survival factor, also regulates CD21/35 and CD23 expression. BAFF blockade in wildtype mice down-modulates CD21/35 and CD23 on B cells while survival remains intact, and BAFF exposure causes elevated CD21/35 and CD23 expression. Similar downmodulation is observed in bcl-2-transgenic mice treated with a BAFF inhibitor. This is the first evidence that BAFF has a function independent of B cell survival. Reports using CD21/35 and CD23 expression to assess splenic B cell subsets in BAFF-null mice concluded a lack of B cells beyond the immature stage. Since CD21/35 and CD23 are inadequate for delineating B cell subpopulations in BAFF-null mice, we used expression of BAFF-R and several B cell markers to identify more mature splenic B cells in these mice. These data broaden our understanding of BAFF function and correct the view that BAFF-null mice lack mature B cells.
Journal of immunology (Baltimore, Md. : 1950), 2004
The TNF family cytokine B cell-activating factor belonging to the TNF family (BAFF) (BLyS) plays a fundamental role in regulating peripheral B cell survival and homeostasis. A BAFF-specific receptor (BAFF-R; BR3) appears to mediate these functions via activation of the NF-kappaB2 pathway. Signaling by the BAFF-R is also required to sustain the germinal center (GC) reaction. Engagement of this receptor results in the induction of Bcl-2, suggesting that this antiapoptotic factor acts downstream of the BAFF-R and NF-kappaB2 pathway to promote peripheral B cell survival during primary and Ag-driven development. To test this idea, we created lines of mice coexpressing a Bcl-2 transgene and a signaling-deficient form of the BAFF-R derived from the B lymphopenic A/WySnJ strain. Surprisingly, although dramatically elevated numbers of B cells accumulate in the periphery of these mice, these B cells exhibit extremely perturbed primary development, formation of lymphoid microenvironments, and ...
Novel function of TNF cytokines in regulating bone marrow B cell survival
Cellular & molecular immunology, 2004
Two newly identified tumor necrosis factor (TNF) family cytokines, B cell activation factor from the TNF family (BAFF) and a proliferation-inducing ligand (APRIL), have recently been shown to enhance the maturation and survival of peripheral B cells. However, whether BAFF and APRIL are expressed in the bone marrow (BM) microenvironment and if these two cytokines modulate early B cell development remain unclear. In the present study, we have detected the abundant expression of BAFF and APRIL transcripts in BM non-lymphoid cells. Low levels of BAFF and APRIL mRNA are also found in developing B cells. Furthermore, we have determined the expression patterns of BAFF receptors during B lymphopoiesis. In cultures, both recombinant BAFF and APRIL significantly promote the survival of precursor B cells whereas only BAFF can suppress apoptosis of immature B cells. These findings suggest that BAFF and APRIL, in addition to their well established role in regulating peripheral B cell growth, can...