Figure 8.

Ligation of SIRPα impairs the reorganization of surface FcγRI. (A) Human macrophages were incubated for 24 h in wells coated with PLL, 20 µg/ml of hCD47, or with increasing concentrations of hCD47 in the presence of 10 µg/ml of hIgG, as indicated. M-CSF release was assessed by ELISA. Bars represent mean ± SD from three donors. Each color represents one individual donor. (B) TIRF images of FcγRI at the surface of human macrophages incubated for 10 min on slides coated with hCD47 or hCD47 plus hIgG and stained with fluorescently labeled specific antibody. Bars, 10 µm. (C) TIRF and dSTORM images showing FcγRI (green) and SIRPα (red) at the surface of human macrophages incubated for 10 min on slides coated with hCD47 (top) or hCD47 plus hIgG (bottom) and stained with anti–FcγRI-AF488 and anti–SIRPα-AF647 mAbs. Bars, 5 µm. In each condition, regions outlined by the white squares (middle column) are shown enlarged (right column) with relative fluorescence intensity profiles along the white lines. Bars, 1 µm. (D and G) CBC histograms of the single-molecule distributions of the colocalization parameter for FcγRI and SIRPα (D) and for FcγRI and pSHP-1Y536 (G) in cells seeded onto slides coated with PLL (light gray), hCD47 (light red), hCD47 plus hIgG (dark red), or hIgG (dark gray) for 10 (D) or 5 min (G). Data are from a minimum of 30 cells from three independent donors. Bars represent mean ± SD. (E and H) NND analysis from data shown in D and G, respectively. Each symbol represents the median NND of all paired single-molecule localizations from one cell. Horizontal lines and error bars represent mean ± SD. ns, not significant; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; one-way ANOVA with Tukey’s post-hoc test. (F and I) Histogram distributions of the NND between the centroids of nanoclusters from one channel and the centroid of their nearest neighbor from the second channel (≥20,000 clusters from a minimum of 10 cells per condition). Graphs compare colocalization between FcγRI and SIRPα (F) and FCγRI and pSHP-1Y536 (I). a.u., arbitrary units; NN, nearest neighbor; PC, positive control.

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