CSF1 and Wiskott-Aldrich syndrome: Since the observed kinetics of the first wave of increase in F-actin content coincided with our previously published kinetics of WASp activation status in response to CSF-1 [17], we repeated the CSF-1 upshift experiment using shWASp RAW/LR5 cells, which have significantly reduced WASp expression and have been previously shown to recapitulate the chemotactic defects observed in macrophages isolated from patients with Wiskott-Aldrich syndrome [18].