Tyrosine phosphorylation of RAFTK in THP1 monocytic cells and primary MMs. THP1 cells (20 × 10⁶) were stimulated with either (A) 1,000 U/mL CSF-1/M-CSF or (B) 2 μg/mL LPS for the indicated time periods. (C) MMs (20 × 10⁶) were allowed to adhere and mature in culture for 7 to 14 days before their stimulation with 1,000 U/mL CSF-1/M-CSF. Cell lysates prepared in RIPA buffer were subjected to immunoprecipitation with anti-RAFTK antibody or normal rabbit serum as a control. Anti-RAFTK immunoprecipitates were resolved by 7.5% SDS-PAGE, transferred to nitrocellulose membranes, and immunoblotted with antiphosphotyrosine antibody (4G10) (top panel). The same blot was subjected to serial immunoblotting with anti-RAFTK antibody (bottom panel). TCL, total cell lysates; NRS, normal rabbit serum control.