Signal scatter plots comparing the intensities of gene expressions on microarray chips within Ficoll and CPT-derived PBMC and their immune cell subsets for each healthy donor tested. The expression signals of Ficoll-derived cells were plotted against the expression signals of CPT-derived cells for each cell type and donor. A line of perfect correlation is indicated in all plots. Pearson's correlation coefficients between each pair of samples are shown at the bottom right of each plot. The data showed that the pattern of gene expression was very similar between Ficoll and CPT-derived cell types, as indicated by the high correlation coefficients