Time course analysis of tyrosine phosphorylation and dephosphorylation of CBL and its association with the CRKL adapter protein following FcγR1 activation. Anti-phosphotyrosine immunoblot was performed on CBL immunoprecipitated from U937 cells with anti-phosphotyrosine antibody (4G10). Lane 1, preimmune (1 mg/ml rabbit IgG) and lane 2, resting U937 cells (NS). FcγR1 stimulation [32.2mAb F(ab)2] and crosslinking with rabbit anti mouse antisera to U937 cells were done for 1, 5, 10, 20, 40 & 60 min., lane 3 to 8 respectively. Lane 9, whole cell lysate (WCL). This blot was again reprobed with anti-CBL and anti-CRKL antibody to confirm equal precipitation of CBL in all lanes and its association with CRKL. This experiment was repeated three times.