Ex vivo effect of rapamycin on D816V human mast cells. (A) Effect of rapamycin and imatinib on D816V c-kit–mutated mast cells isolated from bone marrow of a patient with systemic mastocytosis. Cells were incubated in the presence of different concentrations of imatinib (0.1 to 1 μM; top panel) or rapamycin (5 and 50 nM; bottom panel) for 4 days. Data represent one experiment plated in duplicate. (B) Effect of rapamycin and imatinib on cord blood–derived human mast cells from healthy donors. Histogram represents the survival cell number after 6 days of treatment. Results represent 1 of 4 separate experiments plated in triplicate.