Optimization of immunomagnetic selection of myeloma cells from bone marrow using magnetic activated cell sorting.

Plasma cells (PCs) enrichment from bone marrow samples of multiple myeloma (MM) patients is frequently performed by immunomagnetic separation (magnetic activated cell sorting, MACS) using anti-CD138 MicroBeads. The aim of our work was to find optimal strategy for immunomagnetic separation of PCs and determine optimal algorithm of separation techniques for samples with various percentage of neoplastic cells. From 2007 to 2008, selection of PCs using separation programs Possels and Posseld(2) was carried out on 234 bone marrow samples obtained from 208 MM patients. In 2008, an optimal algorithm for separation programs was introduced based on the analysis of the previous experiments. The Possels program is applicable for samples with >10% PCs in the mononuclear fraction, while the Posseld(2) program is used for samples with 5-10% PCs in the mononuclear fraction. Median purity of 92.6% for the positive fraction of cells (range 14.5-99.6%) and median recovery of 60.4% (range 25.7-99.5%) were obtained when the Possels program was applied (n = 45). A total of 80% (36/45) of processed samples had purity of >70%. Median purity for the positive fraction of 83.7% (range 14.3-99.7%) and median recovery of 14.3% (range 3.6-50.0%) were achieved using the Posseld(2) program (n = 99). A total of 68% (67/99) of processed samples reached >70% purity. This separation strategy enabled us to obtain sufficient amounts of highly purified PCs required for subsequent research purposes. The MACS method has been unsuccessful if the percentage of PCs in the initial sample was <5%. These samples were processed by fluorescence activated cell sorting (FACS).