Imatinib inhibits c-fms phosphorylation. (A) FDC-cfms cells were starved for 1 hour in the presence of imatinib, then stimulated with M-CSF for 2 minutes. Immunoprecipitates were examined for α-phosphotyrosine using Western blotting (IC indicates isotype control). (B) Band intensity was normalized from 3 Western blots. (C) The relationship between imatinib concentration and phosphorylation was predicted according to a sigmoidal model and used to calculate an IC₅₀ value. Results are representative of 3 individual experiments. *P < .05). Error bars represent SEM.