Characterization of Cbl-SLP-76 interaction in U937IF cells. We examined the tyrosine phosphorylation of Cbl and SLP-76 in U937IF cells under conditions of anti-FcR (A77) stimulation. (A) Antiphosphotyrosine blot performed on anti-Cbl and anti–SLP-76 immunoprecipitates. Lane 1 is a preimmune immunoprecipitate. Anti-Cbl immunoprecipitation was performed from resting U937IF cells (lane 2) and from U937IF stimulated with anti-FcR and RM (lane 3). Anti–SLP-76 immunoprecipitates of resting (lane 4) and U937IF cells stimulated with anti-FcR and RM for 1 minute (lane 5). (B) Anti-Cbl (upper panel) and anti–SLP-76 (lower panel) immunoblots performed on the same membrane of (A) after stripping with 0.1 mol/L glycine, pH 2.5, at room temperature for 30 minutes. Lanes are identical to those in (A).