FACS analysis of CMFDGlu-loaded Gaucher fibroblasts or PFBFDGlu-loaded Gaucher PBMC. MFG-GC transduced and nontransduced Gaucher fibroblasts (A) or Gaucher and control PBMC (C), were incubated at 37°C for 5 to 30 minutes in the presence of 1 mmol/L CMFDGlu (for 5, 10, or 30 minutes) or PFBFDGlu (for 5, 15, or 30 minutes), respectively. The fluorescence histograms of fibroblasts or large PBMC (FS, OS scatter high) for each time point are overlaid to indicate the relative fluorescence levels of each pair of samples (upper panel, Gaucher fibroblasts: — nontransduced, — transduced; lower panel, FS, OS large PBMC isolated from: — Gaucher patients, or — controls). The MF values of nontransduced fibroblasts or Gaucher patient FS, OS large cells are shown in the upper left corner of each histogram. The MF values of transduced fibroblasts or control FS, OS large cells are shown in the upper right corner. The MF values are plotted versus time in (B) and (D) for each of the samples displayed in A and C, respectively. The MF ratio is determined by subtracting the MF of cells incubated in the absence of substrate, and taking the ratio of the corrected MF values.