Effect of engagement of cell surface molecules on tyrosine phosphorylation of p72Syk and p120Cbl. MO7e cells were cross-linked with the indicated antibodies for 10 minutes at 37°C. (A) Cell lysates were immunoprecipitated with anti-Syk Ab and followed by immunoblotting with antiphosphotyrosine MoAb (upper panel) and reprobing with anti-Syk Ab (lower panel). (B) Cell lysates were immunoprecipitated with anti-Cbl Ab and followed by immunoblotting with antiphosphotyrosin MoAb (upper panel) and reprobing with anti-Cbl Ab (lower panel). The tyrosine-phosphorylated band around 130 kD in the lanes from cell lysates stimulated with anti-CD31 MoAb is supposed to be CD31 molecule bound to protein A through the antibody used for cross-linking. These are the representative results from two separate experiments.
