Partial block in B lymphocyte development at the transition into the pre-B cell receptor stage in Vpre-B1-deficient mice

The surrogate light chain (SL) is composed of two polypeptides, Vpre-B and λ5. In large pre-BII cells the SL chain associates with Ig μ heavy chain (μH) to form the pre-B cell receptor (pre-BCR). In mice there are two Vpre-B genes which are 98% identical within the coding regions. The two genes are co-expressed at the RNA level and encode functional proteins that can assemble with λ5. However, it is not known whether both gene products serve the same function in vivo. Here we have established mice that lack the Vpre-B1 gene (VpreB1-/-), but still express the Vpre-B2 gene, both as RNA and protein. In Vpre-B1-/- mice, the bone marrow cellularity and the percentage of B220+ cells is normal. However, among the B220+ cells, the percentage of pre-BI cells is increased, and the percentage of pre-BII and immature B cells is slightly decreased, suggesting that the lack of Vpre-B1 causes a partial block at the transition from pre-BI to pre-BII cells, i.e. into the pre-BCR stage. The number of cells that produce a functional pre-BCR is thus lower, but the cells that reach this stage are normal as they can be expanded by proliferation and then differentiate into more mature cells. The spleens of Vpre-B1 homozygous mutant mice show normal numbers of B and T lymphocytes. Moreover, the Ig loci are allelicly excluded and the homozygous mutant mice respond with normal levels of antigen-specific antibodies to T-dependent antigens. These results demonstrate that Vpre-B2 alone is capable of supporting B lymphocyte development in the bone marrow and can give rise to immuno-competent cells in the peripher

A Study of the Surrogate Light chain

This thesis has investigated the importance of the VpreB1 protein in early B cell development. Mice lacking the VpreB1 protein showed normal numbers of peripheral mature B cells. The number of B220 positive cells in the bone marrow was also normal, but the amounts of pre-BI cells was increased 2-fold and the numbers of pre-B II cells were reduced by 20%. In all other respects the lymphoid compartments were normal. The conclusion was that the VpreB1 protein is not necessary for the generation of B cells, and in the presence of the VpreB2 protein B lymphocytes develop normally and give rise to immuno competent cells in the periphery. In the second part of the thesis, the regulation of lambda5 and VpreB1 gene expression was investigated. A novel enhancer was isolated upstream of the VpreB1 gene and the core of the lambda5 enhancer was defined. Both enhancers contain elements that restrict reporter gene expression to pre-B cells when tested in cell lines. The transcription factors EBF and PEBP2 were shown to interact with both enhancers in EMSAs. These binding sites were crucial for lambda5 enhancer activity but less so for the VpreB1 enhancer. An E-box, potentially binding products of the E2A gene, E47 or E12, was shown to be functionally important for the lambda5 enhancer. In addition, the proto-oncogene c-myb was shown to interact with a functionally important element in the lamba5 core enhancer

Location of Retroperitoneal Lymph Node Metastases in Upper Tract Urothelial Carcinoma: Results from a Prospective Lymph Node Mapping Study

Background: There is limited information on the distribution of retroperitoneal lymph node metastases (LNMs) in upper tract urothelial carcinoma (UTUC). Objective: To investigate the location of LNMs in UTUC of the renal pelvis or proximal ureter and short-term complications after radical nephroureterectomy (RNU) with lymph node dissection (LND). Design, setting, and participants: This was a prospective Nordic multicenter study (four university hospitals, two county hospitals). Patients with clinically suspected locally advanced UTUC (stage >T1) and/or clinical lymph node–positive (cN+) disease were invited to participate. Participants underwent RNU and fractionated retroperitoneal LND using predefined side-specific templates. Outcome measurements and statistical analysis: The location of LNMs in the LND specimen and retroperitoneal lymph node recurrences during follow-up was recorded. Postoperative complications within 90 d of surgery were ascertained from patient charts. Descriptive statistics were used. Results and limitations: LNMs were present in the LND specimen in 23/100 patients, and nine of 100 patients experienced a retroperitoneal recurrence. Distribution per side revealed LNMs in the LND specimen in 11/38 (29%) patients with right-sided tumors, for whom the anatomically larger, right-sided template was used, in comparison to 12/62 (19%) patients with left-sided tumors, for whom a more limited template was used. High-grade complications (Clavien grade ≥3) within 90 d of surgery were registered for 13/100 patients. The study is limited in size and not powered to assess survival estimates. Conclusions: The suggested templates that we prospectively applied for right-sided and left-sided LND in patients with advanced UTUC included the majority of LNMs. High-grade complications directly related to the LND part of the surgery were limited. Patient summary: This study describes the location of lymph node metastases in patients with cancer in the upper urinary tract who underwent surgery to remove the affected kidney and ureter. The results show that most metastases occur within the template maps for lymph node surgery that we investigated, and that this surgery can be performed with few severe complications