A rapid two-step method for elimination of bcl-2/IgH positive non-Hodgkin's lymphoma cells from human blood or marrow stem cells, employing immunomagnetic purging with streptavidin-coated ferrofluids.

ABSTRACT

BACKGROUND: Follicular lymphoma cells may contaminate blood or BM stem cell collections used for autologous transplants and contribute to relapse. We report on the development of a B-cell lymphoma-purging technique, using streptavidin-coated ferrofluids (SAFF) and a high-gradient magnetic-separation device (HGMSD). METHODS: Blood or BM samples were spiked with bcl-2 positive lymphoma cells, labeled with biotinylated B cell MAb (CD19, CD20, CD37) then purged by positive selection of CD34(+) cells, followed by negative selection with SAFF and a high HGMSD. Purging efficiency was judged by dual-labeled flow cytometry and by PCR analysis of bcl-2. RESULTS: A 6 log purge of bcl-2 lymphoma cells could be achieved by first enriching for CD34(+) cells, followed by negative selection with SAFF and HGMSD. The use of SAFF with HGMSD alone could only accomplish a 2-3 log purge. DISCUSSION: CD34 selection from blood or BM of follicular lymphoma patients, followed by negative selection of MAb-labeled cells with SAFF could achieve a 6 log purge. However, cell yields were low (10%) and purging efficacy was limited to low starting concentration of lymphoma cells (< or = 1.0%). This technique, however, may be useful for full-scale clinical purging of minimal residual disease following debulking with a cyclophosphamide or other agents.