Expression of CD19 and CD34 on PBMC of MM patients. Representative staining by MoAb to CD34 and CD19 on PBMC from a myeloma patient. PBMC from myeloma patients were stained in dual IF with CD19-FITC and 8G12-PE (CD34), or isotype-matched control MoAb in direct IF. For each patient, positive staining was determined by comparison with the isotype-matched controls. Each row represents one patient. For these patients, the rectangles identify the sort windows for purification of CD34⁺19⁺ and CD34⁻19⁺ MM PBMC (left panels). Reanalysis of sorted subsets indicated the percent purity recorded within each sort window (middle and right panels). Overall, for CD34⁺19⁺ sorts 98% ± 0.7% were within the selected sort window and had 0.26% ± 0.3% cells from the other sort window; for CD34⁻19⁺ sorts 97% ± 0.5% were within the selected sort window and 0.5% ± 0.6% were from the other sort window (values are mean ±SD).