Binding of biotinylated SIRP1ex to PB cells. Mononuclear PB cells were incubated for 30 minutes with biotinylated SIRP1ex protein and labeled with SA-PE. Histograms show binding of biotinylated SIRP1ex to gated lymphocytes (LY), monocytes (MO), or granulocytes (GRA), analyzed on a FACSCalibur flow cytometer. Results are presented as the ▵ median fluorescence intensity of the biotinylated SIRP1ex signal (filled histogram) versus the control signal (black line), where biotinylated GST was used (n = 6).