U937 cells were crosslinked with control IgG or anti-CD13 452 mAb (1.0 μg/mL) for indicated period of time, lysates immunoprecipitated with biotinylated anti-CD13 mAbs and probed for A) IQGAP1 and CD13 or B)α-actinin and CD13. C, D) U937 monocytes were pretreated with vehicle or Src Kinase inhibitors PP2 or Herbimycin for 30 min, crosslinked with control IgG or 452 mAb for 30 min, lysates were immunoprecipitated with biotinylated anti-CD13 mAbs and probed for α-actinin and CD13. E) U937 cells were cross-linked with control IgG or anti CD13 452 mAb for the indicated periods of time, lysates immunoprecipitated with biotinylated anti-pTyr antibody and probed for α-actinin1 and CD13. Graphs of quantitative Western blot data combine 3 separate experiments.