Simultaneous immunomagnetic CD34+cell selection and B-cell depletion in peripheral blood progenitor cell samples of patients suffering from B-cell non-Hodgkin's lymphoma

The reduction of residual tumor cells is one of the main targets of leukaph eresis product (LP) processing. Immunomagnetic enrichment/selection of CD34 + progenitor cells (Baxter Isolex 300i) can achieve a reduction of contamin ating B-cells of approximately 2-3 logs in B-cell non-Hodgkin's lymphoma pa tients. Specific release of the enriched CD34+ cells (stem cell releasing a gent PR34+; Baxter) and the use of antibody-coated immunobeads targeted aga inst B-cell markers (CD10, CD19, CD20, CD22, CD23, and CD37) during this pr ocedure allows the GMP-like simultaneous capture of residual B cells within a closed system. This combination of two purging techniques enhances the B -cell depletion capacity up to 4.5 logs. By performing 10 clinical-scale pu rging procedures, we could show that the simultaneous immunomagnetic purgin g method is easy to perform and highly efficient. We evaluated B-cell log d epletion by flow cytometry for cases with marker-positive cells detectable before and after the purging procedure. The mean reduction of B-cells in th ese cases was 3.5 logs; the mean CD34+ cell yield and purity were 47 and 92 %, Using three LPs, we tested the procedure on a modified Baxter Isolex 300 i device with software adaptations for this procedure (software version 2.0 ) in direct comparison with CD34+ cell selection only, using the former ver sion (version 1.12), The CD34+ cell yield was 49% (40-54%) for the CD34+ ce ll selection and 51% (19-72%) for simultaneous double selection, The mean p urity was 96% for CD34+ cell selection and 98% for simultaneous double sele ction. B-cell depletion was 1.9 logs for CD34+ cell selection, and after si multaneous double selection, the B-cell content was decreased by 3.7 log st eps (P = 0.0495), Clinical application of double-purged cells has not prolo nged the hematopoietic recovery times after high-dose therapy as compared w ith nonpurged peripheral blood progenitor cell autotransplants, In conclusi on, we could show that the simultaneous double selection protocol developed leads to a highly increased B-cell purging efficacy when compared with CD3 4+ cell selection without any negative effects regarding CD34+ cell yield a nd engraftment times after high-dose therapy.