IL-7 is critical for B cell production in adult mice; however, its role in human B lymphopoiesis is controversial. One challenge was the inability to differentiate human cord blood (CB) or adult bone marrow (BM) hematopoietic stem cells (HSCs) without murine stroma. Here, we examine the role of IL-7 in human B cell development using a novel, human-only model based on coculturing human HSCs on primary human BM stroma. In this model, IL-7 increases human B cell production by >60-fold from both CB and adult BM HSCs. IL-7-induced increases are dose-dependent and specific to CD19 ؉ cells. STAT5 phosphorylation and expression of the Ki-67 proliferation Ag indicate that IL-7 acts directly on CD19 ؉ cells to increase proliferation at the CD34 ؉ and CD34؊ pro-B cell stages. Without IL-7, HSCs in CB, but not BM, give rise to a small but consistent population of CD19 lo B lineage cells that express EBF (early B cell factor) and PAX-5 and respond to subsequent IL-7 stimulation. Flt3 ligand, but not thymic stromal-derived lymhopoietin (TSLP), was required for the IL-7-independent production of human B lineage cells. As compared with CB, adult BM shows a reduction of in vitro generative capacity that is progressively more profound in developmentally sequential populations, resulting in an ϳ50-fold reduction in IL-7-dependent B lineage generative capacity. These data provide evidence that IL-7 is essential for human B cell production from adult BM and that IL-7-induced expansion of the pro-B compartment is increasingly critical for human B cell production during the progression of ontogeny. M urine studies have provided evidence that B cell development is controlled by a network of transcription factors and cytokine signaling that coordinates stagespecific expression of B lineage genes (1, 2). In mice, signaling through two cytokine receptors, Flt3 and IL-7R, are critical for B cell development. The combined loss of signaling through both of these receptors completely blocks fetal and adult B cell development (3, 4). Flt3 signaling up-regulates IL-7R␣ expression (5). In adult mice, signaling through the IL-7R up-regulates expression of early B cell factor (EBF).3 EBF in turn regulates expression of a cascade of B cell-specific genes (1, 2) required for the transition from the common lymphoid progenitor to pro-B cells (6 -8). During fetal and neonatal life, IL-7-independent expression of EBF allows early B lineage differentiation, but not proliferation, unless IL-7 is present (9). Human B cell development is thought to differ from that in mouse with respect to the requirement for IL-7. Early evidence for the importance of IL-7 in murine B cell production came from in vitro studies showing that B cell precursors derived from adult bone marrow (BM) increase by ϳ50-fold with the addition of IL-7 (10). Further evidence came from reports of blocked B cell development in the initial in vivo studies that characterized mutant mice with defects in IL-7 (11), or in components of the IL-7R (12, 13). Parallel in vitro studies of human B ce...

Diffusion-weighted imaging (DWI) and consequent apparent diffusion coefficient (ADC) maps have been used for lesion detection and as a predictor of outcome in adults with traumatic brain injury (TBI), but few studies have been reported in children. We evaluated the role of DWI and ADC for outcome prediction after pediatric TBI (n=37 TBI; n=10 controls). Fifteen regions of interest (ROIs) were manually drawn on ADC maps that were grouped for analysis into peripheral gray matter, peripheral white matter, deep gray and white matter, and posterior fossa. All ROIs excluded areas that appeared abnormal on T2-weighted images (T2WI). Acute injury severity was measured using the Glasgow Coma Scale (GCS) score, and 6-12-month outcomes were assessed using the Pediatric Cerebral Performance Category Scale (PCPCS) score. Patients were categorized into five groups: (1) controls; (2) all TBI patients; (3) mild/moderate TBI with good outcomes; (4) severe TBI with good outcomes; and (5) severe TBI with poor outcomes. ADC values in the peripheral white matter were significantly reduced in children with severe TBI with poor outcomes (72.8+/-14.4x10(-3) mm2/sec) compared to those with severe TBI and good outcomes (82.5+/-3.8x10(-3) mm2/sec; p<0.05). We also found that the average total brain ADC value alone had the greatest ability to predict outcome and could correctly predict outcome in 84% of cases. Assessment of DWI and ADC values in pediatric TBI is useful in evaluating injury, particularly in brain regions that appear normal on conventional imaging. Early identification of children at high risk for poor outcome may assist in aggressive clinical management of pediatric TBI patients.

Magnetic resonance imaging (MRI) is increasingly used in the assessment of the severity and progression of neurotrauma. We evaluated temporal and regional changes after mild fluid percussion (FPI) and controlled cortical impact (CCI) injury using T2-weighted-imaging (T2WI) and diffusion-weighted imaging (DWI) MRI over 7 days. Region of interest analysis of brain areas distant to the injury site (such as the hippocampus, retrosplenial and piriform cortices, and the thalamus) was undertaken. In the hippocampus of CCI animals, we found a slow increase (51%) in apparent diffusion coefficients (ADC) over 72 h, which returned to control values. The hippocampal T2 values in the CCI animals were elevated by 18% over the 7-day time course compared to control, indicative of edema formation. Histological analysis supported the lack of overt cellular loss in most brain regions after mild CCI injury. FPI animals showed a generalized decrease in hippocampal ADC values over the first 72 h, which then returned to sham levels, with decreased T2 values over the same period, which remained depressed at 7 days. Histological assessment of FPI animals revealed numerous shrunken cells in the hippocampus and thalamus, but other regions showed little damage. Increased immunohistochemical staining for microglia and astroglia at 7 days post-injury was greater in FPI animals within the affected brain regions. In summary, traumatic brain injury is less severe in mild CCI than FPI, based on the temporal events assessed with MRI.

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OBJECTIVES-This study evaluates the efficacy of combining proton irradiation with gemcitabine and the role the inhibitor of apoptosis proteins (IAP) survivin & XIAP play in the radiosensitive vs. radioresistant status of pancreatic cancer. METHODS-The radioresistant (PANC-1) and radiosensitive (MIA PaCa-2) pancreatic carcinoma cells response to combined gemcitabine and proton irradiation was compared. Cells were treated with 0.1 -500 μ-M gemcitabine and 0 -15 Gy proton irradiation after which Trypan blue and flow cytometry were utilized to determine changes in the cell cycle and apoptosis. Expression levels of survivin were measured using Western blotting. Combination therapy with 24 h gemcitabine followed by 10-Gy proton irradiation proved most effective. CONCLUSIONS-Our data demonstrate that combining gemcitabine and proton irradiation enhances apoptosis in human pancreatic cancer cells when XIAP levels decrease. Therefore, XIAP may play an important role in human pancreatic cancer proton radioresistance. RESULTS-Gemcitabine