CD34 SELECTION FOR PURGING IN MULTIPLE-MYELOMA AND ANALYSIS OF CD34(-CELL PRECURSORS() B)

Selection of CD34(+) hematopoietic progenitor cells from autografts ma y be performed in multiple myeloma (MM) to minimize contamination with tumor cells. This approach is based on the assumption that the malign ant cells do not express the CD34 antigen. Therefore, we first compare d the CD34(+)/CD10(+) and CD34(+)/CD19(+) subpopulations from bone mar row (BM) and peripheral blood (PB) of fourteen MM patients and five no rmal controls. No difference between the respective early B cell subse ts of both groups could be observed. Using tricolor flow cytometry, th e CD19 expression on CD34(+)/CD10(+) cells in BM was found to increase continuously from CD19(-) to CD19(dlim). In contrast, circulating CD3 4(+)/CD10(+) cells did not coexpress the CD19 antigen. This population may contain myeloid progenitor cells or bipotential progenitor cells of the myeloid and lymphoid lineage as suggested by data obtained with fetal liver cells. Further functional studies are required. Enrichmen t of CD34(+) cells with immunomagnetic beads was performed from BM of three MM patients and four normal donors. The CD34(+) cells were selec ted with the HPCA-1 antibody and detached from the beads with chymopap ain. Compared with the starting cell preparation, a 3.97 +/- 0.48 log (mean +/- SE) reduction of plasma cells could be achieved after CD34 s election. On morphological examination, 84% +/- 4% of the cells in the CD34(+) fraction (MM) were immature blasts. The plating efficiency fo r hematopoietic colony forming cells was 9.7% +/- 2.8% in the CD34 sel ected fraction of the MM group, reflecting a 51-fold increase as compa red with the starting population. However, the mean recovery of colony forming precursor cells was only 19% +/- 8% in the MM samples and 30% +/- 9% in the control samples. The selection of CD34(+) hematopoietic cells is an effective purging method in MM that may be used for autog rafts, provided the recovery can be improved.