Development of Dendritic Cells from GM-CSF-/- Mice in vitro : GM-CSF Enhances Production and Survival of Cells

The production of dendritic cells (DC) from haemopoietic progenitors maintained in long term stroma-dependent cultures (LTC) of spleen or bone marrow (BM) occurs independently of added granulocyte/macrophage colony stimulating factor (GM-CSF). The possibility that cultures depend on endogenous GM-CSF produced in low levels was tested by attempting to generate LTC from spleen and BM of GM-CSF-/- mice. Multiple cultures from GM-CSF-/- and wild type mice were established and compared for cell production. GM-CSF-/- LTC developed more slowly, but by 16 weeks produced cells resembling DC in numbers comparable to wild type cultures. LTC maintained distinct populations of small and large cells, the latter resembling DC. Cells collected from GM-CSF-/- LTC were capable antigen presenting cells (APC) for T cell stimulation and morphologically resembled DC. Large cells expressed the CD11b, CD11c, CD86, 33D1 and Dec-205 markers of DC. Addition of GM-CSF to GM-CSF-/- LTC increased the proportion of large, mature DC present in culture. Stromal cells from GM-CSF-/- LTC could support the differentiation of DC from early progenitors maintained in LTC without addition of GM-CSF. However, GM-CSF is not a critical factor in the in vitro generation of DC from progenitors. It can, however, substitute for stromal cells in increasing the survival of mature DC

Direct and indirect effects of climate on richness drive the latitudinal diversity gradient in forest trees

Data accessibility statement: Full census data are available upon reasonable request from the ForestGEO data portal, http://ctfs.si.edu/datarequest/ We thank Margie Mayfield, three anonymous reviewers and Jacob Weiner for constructive comments on the manuscript. This study was financially supported by the National Key R&D Program of China (2017YFC0506100), the National Natural Science Foundation of China (31622014 and 31570426), and the Fundamental Research Funds for the Central Universities (17lgzd24) to CC. XW was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB3103). DS was supported by the Czech Science Foundation (grant no. 16-26369S). Yves Rosseel provided us valuable suggestions on using the lavaan package conducting SEM analyses. Funding and citation information for each forest plot is available in the Supplementary Information Text 1.Peer reviewedPostprin

Spleen stromal cells support haemopoiesis and in vitro growth of dendritic cells from bone marrow

Long-term stroma-dependent cultures from murine spleen have been previously shown to support dendritic cell (DC) development in vitro. Secondary cultures have now been established using a splenic stromal cell layer overlaid with cells from different lymphoid sites. Cells resembling DCs can be generated in vitro from unfractionated murine lymphoid cells in the absence of added growth factors. Bone marrow (BM) cultures are the most successful but some cultures have been derived from spleen and thymus. Large numbers of mononuclear cells with dendritic morphology can be generated from BM within 2 weeks and cell production in many cultures has been maintained for at least 6 months. A significant proportion of cells binds antibodies specific for DC markers. No lymphoid cells, mast cells or granulocytes are detectable in culture by antibody and histochemical staining and light and electron microscopy. As with cells generated in primary cultures, cells grown in secondary cultures are equally potent stimulators of both syngeneic and allogeneic mixed lymphocyte reactions, confirming their function as antigen- presenting cells. They are also capable of endocytosing and presenting protein antigen to the D10.G4.1 Th2 clone and to unprimed T cells. This study confirmed the presence of DC precursors in multiple lymphoid sites which can be induced to proliferate in the presence of a spleen stromal cell monolayer. The secondary culture system provides an ideal in vitro model for investigation of the development of DC from different tissue sites. It also provides a stable and continuous resource of cells for further studies on DC development

Improved FACS analysis confirms generation of immature dendritic cells in long-term stromal-dependent spleen cultures

Cells produced in spleen stroma-dependent long-term cultures (LTC) have now been clearly defined as dendritic cells (DC). Characterization of cells by antibody staining and FACS analysis has only been possible using a procedure to quench the high autofluorescence of DC produced in LTC (LTC-DC). The population of large cells produced by the established LTC-X1 culture are homogeneously positive for a number of cell-surface markers expressed by DC. These include CD11c, CD11b, Dec-205, Fc receptor and CD86. They also express markers detectable with the F4/80 and 33D1 antibodies. Cells produced in LTC do not uniformly express the MHC II marker, consistent with an immature DC phenotype. Most cells are weakly positive for MHC II with a small subset of highly positive cells. The quenching method involves staining cells with crystal violet dye, which is taken up within the cell. The importance of optimizimg fluorescent antibody staining assays for delineating DC subsets is indicated and the LTC system is established as a valuable and continuous source of DC precursors

Estimating Rear-End Accident Probabilities at Signalized Intersections: A Comparison Study of Intersections With and Without Green Signal Countdown Devices

<div><p><b>Objective:</b> Rear-end accidents are the most common accident type at signalized intersections, because the diversity of actions taken increases due to signal change. Green signal countdown devices (GSCDs), which have been widely installed in Asia, are thought to have the potential of improving capacity and reducing accidents, but some negative effects on intersection safety have been observed in practice; for example, an increase in rear-end accidents.</p><p><b>Methods:</b> A microscopic modeling approach was applied to estimate rear-end accident probability during the phase transition interval in the study. The rear-end accident probability is determined by the following probabilities: (1) a leading vehicle makes a “stop” decision, which was formulated by using a binary logistic model, and (2) the following vehicle fails to stop in the available stopping distance, which is closely related to the critical deceleration used by the leading vehicle. Based on the field observation carried out at 2 GSCD intersections and 2 NGSCD intersections (i.e., intersections without GSCD devices) along an arterial in Suzhou, the rear-end probabilities at GSCD and NGSCD intersections were calculated using Monte Carlo simulation.</p><p><b>Results:</b> The results suggested that, on the one hand, GSCDs caused significantly negative safety effects during the flashing green interval, especially for vehicles in a zone ranging from 15 to 70 m; on the other hand, GSCD devices were helpful in reducing rear-end accidents during the yellow interval, especially in a zone from 0 to 50 m.</p><p><b>Conclusions:</b> GSCDs helped shorten indecision zones and reduce rear-end collisions near the stop line during the yellow interval, but they easily resulted in risky car following behavior and much higher rear-end collision probabilities at indecision zones during both flashing green and yellow intervals. GSCDs are recommended to be cautiously installed and education on safe driving behavior should be available.</p></div