Specificity of MoAbs B1D5 and B4B6.

(A) 293E/huSIRPβ1 and NIH/3T3/huSIRPα1 cells were immunolabeled with MoAbs SE5A5, B1D5, and B4B6 and stained with PE-conjugated goat antimouse IgG1 or IgG2a antiserum (filled histograms). Nonbinding IgG1 and IgG2a antibodies were used as negative controls (black lines). Cells were analyzed on a FACSCalibur flow cytometer (n = 3). (B) Recombinant SIRPα1ex and SIRPβ1ex protein was immunoprecipitated with MoAbs SE5A5, B1D5, and B4B6. Precipitated protein was separated by 12% SDS-PAGE and immunoblotted with a polyclonal antibody against SIRP (n = 3).