Specificity of anti-SIRP mAbs. Staining of BW and BW-SIRPβ2, BW-SIRPα, BW-SIRPβ1 transfectants (gray profiles) with mAbs LSB2.20 (anti-SIRPβ2, left column), 148 (anti-pan SIRP, middle column), and LSB1.50 (anti-SIRPβ1, right column). Primary antibodies were detected with a PE-conjugated goat antimouse antibody. Thin solid lines represent background staining with mouse control IgG and secondary antibody.