G-CSF hypersensitivity of the p.Pro784Thr CSF3R variant correlates with STAT3 phosphorylation responses. Cells expressing p.Pro784Thr CSF3R or WT CSF3R were serum and cytokine deprived for 2 hours and then stimulated with the indicated concentrations of G-CSF for 30 minutes. (A-B) Whole-cell lysates were immunoblotted with antibodies to phosphorylated STAT5 (pSTAT5), pSTAT3, and β-actin. Representative blots of 3 independent experiments are shown. Densitometric analyses of the immunoblots were performed using ImageJ software. The data are presented as the ratios of pSTAT/β-actin. Error bars show the standard error. *P < .05.