[Kinetics of SLP-76-Cbl interaction following FcγRI stimulation.] Immunoprecipitation was performed with anti–SLP-76 antibody from lysates of resting U937IF cells or cells stimulated by anti-FcγRI cross-linking with MoAb 32.2 F(ab′)₂ fragment for varying periods of time ranging from 30 seconds to 30 minutes. Proteins were resolved by SDS/PAGE, transferred to nitrocellulose membrane, and immunoblotted. (A) Antiphosphotyrosine immunoblot. Lane 1 represents precipitation with preimmune antisera. Lane 2 represents U937IF cells at rest. Lanes 3-7 represent U937IF cells stimulated for 30 seconds, 1 minutes, 5 minutes, 10 minutes, and 30 minutes, respectively. Lane 8 represents whole-cell lysate (1 × 10⁶ cell equivalents) of stimulated U937IF cells. (B) Same membrane as in Fig 2A was blocked and reprobed. Upper panel represents anti-Cbl immunoblot. Middle panel represents anti–SLP-76 immunoblot. Lower panel represents anti-Grb2 immunoblot.