The expression of the mouse VpreB/λ5 locus in transformed cell lines and tumors of the B lineage differentiation pathway

The expression of RNA transcripts from two pre B lymphocyte related genes, VpreB and λ5, has been studied in a series of transformed cell lines which appear frozen at different states of B lineage differentiation, from early progenitors to surface Ig positive B cells. In the HAFTL-1 cell line, which arose from fetal liver by transformation with a retrovlrus containing the Hras oncogene, Northern analysis of poly A+ mRNA as well as in situ hybridization of RNA In single cells revealed that λ5 and VpreB are already expressed at the progenitor stage and increase in expression as the progenitors differentiate to precursor (preB) cells, or are turned off as the progenitors differentiate to myeloid cells. Continued rearrangements of Ig genes in pre B cell lines leading to Ig expression on the surface of NFS-5 pre B cells do not influence the continued expression of VpreB and λ5. Surface Ig-positive B lineage cell lines also express the pre B-related genes. Both Ly1+ as well as Ly1− pre B cells are VpreB and λ5positlve. Lipopolysaccharide (LPS) stimulation of 70Z/3 pre B cells does not turn off λ5 expression. It therefore appears that, at least In transformed cell lines, the expression of VpreB and λ5, is not directly regulated by the expression of μH, κL, or λL chains, LPS reactivity, or the Ly1 surface antigen. Fusion of plasmacytoma cells with normal pre B cells to generate pre B hybridomas leads to down-regulation of VpreB/λ5 expression. These results suggest that different trans-acting factors in more mature cells might down-regulate the expression of VpreB/λ

Accumulation of Multipotent Hematopoietic Progenitors in Peripheral Lymphoid Organs of Mice Over-expressing Interleukin-7 and Flt3-Ligand

Interleukin-7 (IL-7) and Flt3-ligand (FL) are two cytokines important for the generation of B cells, as manifested by the impaired B cell development in mice deficient for either cytokine or their respective receptors and by the complete block in B cell differentiation in the absence of both cytokines. IL-7 is an important survival and proliferation factor for B cell progenitors, whereas FL acts on several early developmental stages, prior to B cell commitment. We have generated mice constitutively over-expressing both IL-7 and FL. These double transgenic mice develop splenomegaly and lymphadenopathy characterized by tremendously enlarged lymph nodes even in young animals. Lymphoid, myeloid and dendritic cell numbers are increased compared to mice over-expressing either of the two cytokines alone and the effect on their expansion is synergistic, rather than additive. B cell progenitors, early progenitors with myeloid and lymphoid potential (EPLM), common lymphoid progenitors (CLP) and lineage−, Sca1+, kit+ (LSK) cells are all increased not only in the bone marrow but also in peripheral blood, spleen and even lymph nodes. When transplanted into irradiated wild-type mice, lymph node cells show long-term multilineage reconstitution, further confirming the presence of functional hematopoietic progenitors therein. Our double transgenic mouse model shows that sustained and combined over-expression of IL-7 and FL leads to a massive expansion of most bone marrow hematopoietic progenitors and to their associated presence in peripheral lymphoid organs where they reside and potentially differentiate further, thus leading to the synergistic increase in mature lymphoid and myeloid cell numbers. The present study provides further in vivo evidence for the concerted action of IL-7 and FL on lymphopoiesis and suggests that extramedullary niches, including those in lymph nodes, can support the survival and maintenance of hematopoietic progenitors that under physiological conditions develop exclusively in the bone marrow

Arginine methylation of the B cell antigen receptor promotes differentiation

Signals processed through the B cell antigen receptor (BCR) control both the proliferation and differentiation of B lymphocytes. How these different signaling modes are established at the BCR is poorly understood. We show that a conserved arginine in the tail sequence of the Igα subunit of the BCR is methylated by the protein arginine methyltransferase 1. This modification negatively regulates the calcium and PI-3 kinase pathways of the BCR while promoting signals leading to B cell differentiation. Thus, Igα arginine methylation can play an important role in specifying the outcome of BCR signaling

Accumulation of Multipotent Hematopoietic Progenitors in Peripheral Lymphoid Organs of Mice Over-expressing Interleukin-7 and Flt3-Ligand

Interleukin-7 (IL-7) and Flt3-ligand (FL) are two cytokines important for the generation of B cells, as manifested by the impaired B cell development in mice deficient for either cytokine or their respective receptors and by the complete block in B cell differentiation in the absence of both cytokines. IL-7 is an important survival and proliferation factor for B cell progenitors, whereas FL acts on several early developmental stages, prior to B cell commitment. We have generated mice constitutively over-expressing both IL-7 and FL. These double transgenic mice develop splenomegaly and lymphadenopathy characterized by tremendously enlarged lymph nodes even in young animals. Lymphoid, myeloid and dendritic cell numbers are increased compared to mice over-expressing either of the two cytokines alone and the effect on their expansion is synergistic, rather than additive. B cell progenitors, early progenitors with myeloid and lymphoid potential (EPLM), common lymphoid progenitors (CLP) and lineage-, Sca1+, kit+ (LSK) cells are all increased not only in the bone marrow but also in peripheral blood, spleen and even lymph nodes. When transplanted into irradiated wild-type mice, lymph node cells show long-term multilineage reconstitution, further confirming the presence of functional hematopoietic progenitors therein. Our double transgenic mouse model shows that sustained and combined over-expression of IL-7 and FL leads to a massive expansion of most bone marrow hematopoietic progenitors and to their associated presence in peripheral lymphoid organs where they reside and potentially differentiate further, thus leading to the synergistic increase in mature lymphoid and myeloid cell numbers. The present study provides further in vivo evidence for the concerted action of IL-7 and FL on lymphopoiesis and suggests that extramedullary niches, including those in lymph nodes, can support the survival and maintenance of hematopoietic progenitors that under physiological conditions develop exclusively in the bone marrow.status: publishe

Fighting chronic lung diseases on a national level:The Dutch national action programme

Introduction: To reduce the burden of chronic lung diseases, the Lung Alliance Netherlands has designed a National Action programme on Chronic Lung Diseases. It aims to improve healthcare coordination, thereby reducing the burden of chronic lung diseases, by focussing on five objectives to be achieved within five years: (1) a 25% reduction in hospitalisation days for asthma and chronic obstructive pulmonary disease; (2) a 15% reduction in working days lost due to respiratory diseases; (3) a 20% improved cost-effectiveness of inhalation medication; (4) a 25% reduction of adolescents taking up smoking; and (5) a 10% reduction of mortality due to asthma and chronic obstructive pulmonary disease. Methods/design: Baseline data were collected from Dutch registries with the most recent available data from 2011, 2012 and 2013. To achieve the objectives, the Lung Alliance Netherlands presented various key activities and strategies that are described in this paper. Discussion: The ambitious objectives are interconnected and their mutual reinforcement is expected to have a beneficial impact on the burden of chronic lung diseases. A strength of the Dutch national action programme is the extensive cooperation between the multiple healthcare parties that contribute to the coordination of the delivery of healthcare. A potential weakness is the relatively short time span of the programme, which may prevent observing its full potential

Soluble BAFF levels inversely correlate with peripheral B cell numbers and the expression of BAFF receptors

The TNF family member protein BAFF/BLyS is essential for B cell survival and plays an important role in regulating class switch recombination as well as in the selection of autoreactive B cells. In humans, increased concentrations of soluble BAFF are found in different pathological conditions, which may be as diverse as autoimmune diseases, B cell malignancies, and primary Ab deficiencies (PAD). Because the mechanisms that regulate BAFF levels are not well understood, we newly developed a set of mAbs against human BAFF to study the parameters that determine the concentrations of soluble BAFF in circulation. Patients with PAD, including severe functional B cell defects such as BTK, BAFF-R, or TACI deficiency, were found to have higher BAFF levels than asplenic individuals, patients after anti-CD20 B cell depletion, chronic lymphocytic leukemia patients, or healthy donors. In a comparable manner, mice constitutively expressing human BAFF were found to have higher concentrations of BAFF in the absence than in the presence of B cells. Therefore, our data strongly suggest that BAFF steady-state concentrations mainly depend on the number of B cells as well as on the expression of BAFF-binding receptors. Because most patients with PAD have high levels of circulating BAFF, the increase in BAFF concentrations cannot compensate defects in B cell development and function

NIM-R7, a novel marker for resting B1 and marginal-zone B lymphocytes, is also expressed on activated T and B cells

In mice, follicular B cells have been studied in detail, while two other B-cell subpopulations – marginal-zone B and B1 cells – are less well understood. In this work we report the expression pattern of p58, a lymphocyte-activation marker, recognized by rat monoclonal antibody, NIM-R7, and present on the latter two cell subpopulations. Staining with NIM-R7 showed that undisturbed marginal-zone B cells, as well as peritoneal cavity and splenic B1a cells, constitutively expressed p58, whereas follicular B cells and resting T lymphocytes did not. Ontogenic analysis of different compartments showed that p58 did not appear at any stage of development, prior to the development of mature T or B2 lymphocytes. Upon polyclonal stimulation, however, p58 appeared on both T and B2 lymphocytes. Finally, ricin A-conjugated NIM-R7 was able to kill the BCL1 lymphoma without effect on mature resting B2 cells. Therefore, p58 may be a potential target for diagnosis or therapy of B1 and marginal-zone B-cell malignancies