Figure 2

CD137L signaling activates microglia in vitro . Microglia cells were grown on plates that had been coated with PBS (grey bars) or 10 μg/mL of Fc control protein (white bars) or 10 μg/mL of CD137-Fc protein (black bars). (A) Attachment and morphological changes of primary microglia were documented by photography (40× magnification) 1 h after plating. Scale bar: 20 μm. (B) Attachment and morphological changes of BV-2 and N9 cells and primary microglia were documented by photography (63×) 24 h after plating. Cells exposed to immobilized CD137-Fc protein developed long spiky projections* and became amoeboid cells^ with shortened protrusions^#. Scale bar: 20 μm. (C) The concentrations of cytokines in supernatants of primary microglia were determined by ELISA at indicated time points. Depicted are means ± standard deviations of triplicate measurements. (D) The phagocytic capacity of the cells was determined by adding FITC-labeled latex beads for 1 h before analysis by flow cytometry. Control: Autofluorescence of the cells. Numbers above the histograms state the percentages of positive cells and mean fluorescence intensities (MFI). These experiments were repeated three times with similar results. * P <0.05; ** P <0.01.